damus

mdb.c (292667B)

---

 /** @file mdb.c
  *	@brief Lightning memory-mapped database library
  *
  *	A Btree-based database management library modeled loosely on the
  *	BerkeleyDB API, but much simplified.
  */
 /*
  * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted only as authorized by the OpenLDAP
  * Public License.
  *
  * A copy of this license is available in the file LICENSE in the
  * top-level directory of the distribution or, alternatively, at
  * <http://www.OpenLDAP.org/license.html>.
  *
  * This code is derived from btree.c written by Martin Hedenfalk.
  *
  * Copyright (c) 2009, 2010 Martin Hedenfalk <martin@bzero.se>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE 1
 #endif
 #if defined(__WIN64__)
 #define _FILE_OFFSET_BITS	64
 #endif
 #ifdef _WIN32
 #include <malloc.h>
 #include <windows.h>
 #include <wchar.h>				/* get wcscpy() */
 
 /** getpid() returns int; MinGW defines pid_t but MinGW64 typedefs it
  *  as int64 which is wrong. MSVC doesn't define it at all, so just
  *  don't use it.
  */
 #define MDB_PID_T	int
 #define MDB_THR_T	DWORD
 #include <sys/types.h>
 #include <sys/stat.h>
 #ifdef __GNUC__
 # include <sys/param.h>
 #else
 # define LITTLE_ENDIAN	1234
 # define BIG_ENDIAN	4321
 # define BYTE_ORDER	LITTLE_ENDIAN
 # ifndef SSIZE_MAX
 #  define SSIZE_MAX	INT_MAX
 # endif
 #endif
 #else
 #include <sys/types.h>
 #include <sys/stat.h>
 #define MDB_PID_T	pid_t
 #define MDB_THR_T	pthread_t
 #include <sys/param.h>
 #include <sys/uio.h>
 #include <sys/mman.h>
 #ifdef HAVE_SYS_FILE_H
 #include <sys/file.h>
 #endif
 #include <fcntl.h>
 #endif
 
 #if defined(__mips) && defined(__linux)
 /* MIPS has cache coherency issues, requires explicit cache control */
 #include <sys/cachectl.h>
 #define CACHEFLUSH(addr, bytes, cache)	cacheflush(addr, bytes, cache)
 #else
 #define CACHEFLUSH(addr, bytes, cache)
 #endif
 
 #if defined(__linux) && !defined(MDB_FDATASYNC_WORKS)
 /** fdatasync is broken on ext3/ext4fs on older kernels, see
  *	description in #mdb_env_open2 comments. You can safely
  *	define MDB_FDATASYNC_WORKS if this code will only be run
  *	on kernels 3.6 and newer.
  */
 #define	BROKEN_FDATASYNC
 #endif
 
 #include <errno.h>
 #include <limits.h>
 #include <stddef.h>
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
 
 #ifdef _MSC_VER
 #include <io.h>
 typedef SSIZE_T	ssize_t;
 #else
 #include <unistd.h>
 #endif
 
 #if defined(__sun) || defined(ANDROID)
 /* Most platforms have posix_memalign, older may only have memalign */
 #define HAVE_MEMALIGN	1
 #include <malloc.h>
 /* On Solaris, we need the POSIX sigwait function */
 #if defined (__sun)
 # define _POSIX_PTHREAD_SEMANTICS	1
 #endif
 #endif
 
 #if !(defined(BYTE_ORDER) || defined(__BYTE_ORDER))
 #include <netinet/in.h>
 #include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
 #endif
 
 #if defined(__FreeBSD__) && defined(__FreeBSD_version) && __FreeBSD_version >= 1100110
 # define MDB_USE_POSIX_MUTEX	1
 # define MDB_USE_ROBUST	1
 #elif defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
 # define MDB_USE_POSIX_SEM	1
 # define MDB_FDATASYNC		fsync
 #elif defined(ANDROID)
 # define MDB_FDATASYNC		fsync
 #endif
 
 #ifndef _WIN32
 #include <pthread.h>
 #include <signal.h>
 #ifdef MDB_USE_POSIX_SEM
 # define MDB_USE_HASH		1
 #include <semaphore.h>
 #else
 #define MDB_USE_POSIX_MUTEX	1
 #endif
 #endif
 
 #if defined(_WIN32) + defined(MDB_USE_POSIX_SEM) \
 	+ defined(MDB_USE_POSIX_MUTEX) != 1
 # error "Ambiguous shared-lock implementation"
 #endif
 
 #ifdef USE_VALGRIND
 #include <valgrind/memcheck.h>
 #define VGMEMP_CREATE(h,r,z)    VALGRIND_CREATE_MEMPOOL(h,r,z)
 #define VGMEMP_ALLOC(h,a,s) VALGRIND_MEMPOOL_ALLOC(h,a,s)
 #define VGMEMP_FREE(h,a) VALGRIND_MEMPOOL_FREE(h,a)
 #define VGMEMP_DESTROY(h)	VALGRIND_DESTROY_MEMPOOL(h)
 #define VGMEMP_DEFINED(a,s)	VALGRIND_MAKE_MEM_DEFINED(a,s)
 #else
 #define VGMEMP_CREATE(h,r,z)
 #define VGMEMP_ALLOC(h,a,s)
 #define VGMEMP_FREE(h,a)
 #define VGMEMP_DESTROY(h)
 #define VGMEMP_DEFINED(a,s)
 #endif
 
 #ifndef BYTE_ORDER
 # if (defined(_LITTLE_ENDIAN) || defined(_BIG_ENDIAN)) && !(defined(_LITTLE_ENDIAN) && defined(_BIG_ENDIAN))
 /* Solaris just defines one or the other */
 #  define LITTLE_ENDIAN	1234
 #  define BIG_ENDIAN	4321
 #  ifdef _LITTLE_ENDIAN
 #   define BYTE_ORDER  LITTLE_ENDIAN
 #  else
 #   define BYTE_ORDER  BIG_ENDIAN
 #  endif
 # else
 #  define BYTE_ORDER   __BYTE_ORDER
 # endif
 #endif
 
 #ifndef LITTLE_ENDIAN
 #define LITTLE_ENDIAN	__LITTLE_ENDIAN
 #endif
 #ifndef BIG_ENDIAN
 #define BIG_ENDIAN	__BIG_ENDIAN
 #endif
 
 #if defined(__i386) || defined(__x86_64) || defined(_M_IX86)
 #define MISALIGNED_OK	1
 #endif
 
 #include "lmdb.h"
 #include "midl.h"
 
 #if (BYTE_ORDER == LITTLE_ENDIAN) == (BYTE_ORDER == BIG_ENDIAN)
 # error "Unknown or unsupported endianness (BYTE_ORDER)"
 #elif (-6 & 5) || CHAR_BIT != 8 || UINT_MAX < 0xffffffff || ULONG_MAX % 0xFFFF
 # error "Two's complement, reasonably sized integer types, please"
 #endif
 
 #if (((__clang_major__ << 8) | __clang_minor__) >= 0x0302) || (((__GNUC__ << 8) | __GNUC_MINOR__) >= 0x0403)
 /** Mark infrequently used env functions as cold. This puts them in a separate
  *  section, and optimizes them for size */
 #define ESECT __attribute__ ((cold))
 #else
 /* On older compilers, use a separate section */
 # ifdef __GNUC__
 #  ifdef __APPLE__
 #   define      ESECT   __attribute__ ((section("__TEXT,text_env")))
 #  else
 #   define      ESECT   __attribute__ ((section("text_env")))
 #  endif
 # else
 #  define ESECT
 # endif
 #endif
 
 #ifdef _WIN32
 #define CALL_CONV WINAPI
 #else
 #define CALL_CONV
 #endif
 
 /** @defgroup internal	LMDB Internals
  *	@{
  */
 /** @defgroup compat	Compatibility Macros
  *	A bunch of macros to minimize the amount of platform-specific ifdefs
  *	needed throughout the rest of the code. When the features this library
  *	needs are similar enough to POSIX to be hidden in a one-or-two line
  *	replacement, this macro approach is used.
  *	@{
  */
 
 	/** Features under development */
 #ifndef MDB_DEVEL
 #define MDB_DEVEL 0
 #endif
 
 	/** Wrapper around __func__, which is a C99 feature */
 #if __STDC_VERSION__ >= 199901L
 # define mdb_func_	__func__
 #elif __GNUC__ >= 2 || _MSC_VER >= 1300
 # define mdb_func_	__FUNCTION__
 #else
 /* If a debug message says <mdb_unknown>(), update the #if statements above */
 # define mdb_func_	"<mdb_unknown>"
 #endif
 
 /* Internal error codes, not exposed outside liblmdb */
 #define	MDB_NO_ROOT		(MDB_LAST_ERRCODE + 10)
 #ifdef _WIN32
 #define MDB_OWNERDEAD	((int) WAIT_ABANDONED)
 #elif defined(MDB_USE_POSIX_MUTEX) && defined(EOWNERDEAD)
 #define MDB_OWNERDEAD	EOWNERDEAD	/**< #LOCK_MUTEX0() result if dead owner */
 #endif
 
 #ifdef __GLIBC__
 #define	GLIBC_VER	((__GLIBC__ << 16 )| __GLIBC_MINOR__)
 #endif
 /** Some platforms define the EOWNERDEAD error code
  * even though they don't support Robust Mutexes.
  * Compile with -DMDB_USE_ROBUST=0, or use some other
  * mechanism like -DMDB_USE_POSIX_SEM instead of
  * -DMDB_USE_POSIX_MUTEX.
  * (Posix semaphores are not robust.)
  */
 #ifndef MDB_USE_ROBUST
 /* Android currently lacks Robust Mutex support. So does glibc < 2.4. */
 # if defined(MDB_USE_POSIX_MUTEX) && (defined(ANDROID) || \
 	(defined(__GLIBC__) && GLIBC_VER < 0x020004))
 #  define MDB_USE_ROBUST	0
 # else
 #  define MDB_USE_ROBUST	1
 # endif
 #endif /* !MDB_USE_ROBUST */
 
 #if defined(MDB_USE_POSIX_MUTEX) && (MDB_USE_ROBUST)
 /* glibc < 2.12 only provided _np API */
 #  if (defined(__GLIBC__) && GLIBC_VER < 0x02000c) || \
 	(defined(PTHREAD_MUTEX_ROBUST_NP) && !defined(PTHREAD_MUTEX_ROBUST))
 #   define PTHREAD_MUTEX_ROBUST	PTHREAD_MUTEX_ROBUST_NP
 #   define pthread_mutexattr_setrobust(attr, flag)	pthread_mutexattr_setrobust_np(attr, flag)
 #   define pthread_mutex_consistent(mutex)	pthread_mutex_consistent_np(mutex)
 #  endif
 #endif /* MDB_USE_POSIX_MUTEX && MDB_USE_ROBUST */
 
 #if defined(MDB_OWNERDEAD) && (MDB_USE_ROBUST)
 #define MDB_ROBUST_SUPPORTED	1
 #endif
 
 #ifdef _WIN32
 #define MDB_USE_HASH	1
 #define MDB_PIDLOCK	0
 #define THREAD_RET	DWORD
 #define pthread_t	HANDLE
 #define pthread_mutex_t	HANDLE
 #define pthread_cond_t	HANDLE
 typedef HANDLE mdb_mutex_t, mdb_mutexref_t;
 #define pthread_key_t	DWORD
 #define pthread_self()	GetCurrentThreadId()
 #define pthread_key_create(x,y)	\
 	((*(x) = TlsAlloc()) == TLS_OUT_OF_INDEXES ? ErrCode() : 0)
 #define pthread_key_delete(x)	TlsFree(x)
 #define pthread_getspecific(x)	TlsGetValue(x)
 #define pthread_setspecific(x,y)	(TlsSetValue(x,y) ? 0 : ErrCode())
 #define pthread_mutex_unlock(x)	ReleaseMutex(*x)
 #define pthread_mutex_lock(x)	WaitForSingleObject(*x, INFINITE)
 #define pthread_cond_signal(x)	SetEvent(*x)
 #define pthread_cond_wait(cond,mutex)	do{SignalObjectAndWait(*mutex, *cond, INFINITE, FALSE); WaitForSingleObject(*mutex, INFINITE);}while(0)
 #define THREAD_CREATE(thr,start,arg) \
 	(((thr) = CreateThread(NULL, 0, start, arg, 0, NULL)) ? 0 : ErrCode())
 #define THREAD_FINISH(thr) \
 	(WaitForSingleObject(thr, INFINITE) ? ErrCode() : 0)
 #define LOCK_MUTEX0(mutex)		WaitForSingleObject(mutex, INFINITE)
 #define UNLOCK_MUTEX(mutex)		ReleaseMutex(mutex)
 #define mdb_mutex_consistent(mutex)	0
 #define getpid()	GetCurrentProcessId()
 #define	MDB_FDATASYNC(fd)	(!FlushFileBuffers(fd))
 #define	MDB_MSYNC(addr,len,flags)	(!FlushViewOfFile(addr,len))
 #define	ErrCode()	GetLastError()
 #define GET_PAGESIZE(x) {SYSTEM_INFO si; GetSystemInfo(&si); (x) = si.dwPageSize;}
 #define	close(fd)	(CloseHandle(fd) ? 0 : -1)
 #define	munmap(ptr,len)	UnmapViewOfFile(ptr)
 #ifdef PROCESS_QUERY_LIMITED_INFORMATION
 #define MDB_PROCESS_QUERY_LIMITED_INFORMATION PROCESS_QUERY_LIMITED_INFORMATION
 #else
 #define MDB_PROCESS_QUERY_LIMITED_INFORMATION 0x1000
 #endif
 #define	Z	"I"
 #else
 #define THREAD_RET	void *
 #define THREAD_CREATE(thr,start,arg)	pthread_create(&thr,NULL,start,arg)
 #define THREAD_FINISH(thr)	pthread_join(thr,NULL)
 #define	Z	"z"			/**< printf format modifier for size_t */
 
 	/** For MDB_LOCK_FORMAT: True if readers take a pid lock in the lockfile */
 #define MDB_PIDLOCK			1
 
 #ifdef MDB_USE_POSIX_SEM
 
 typedef sem_t *mdb_mutex_t, *mdb_mutexref_t;
 #define LOCK_MUTEX0(mutex)		mdb_sem_wait(mutex)
 #define UNLOCK_MUTEX(mutex)		sem_post(mutex)
 
 static int
 mdb_sem_wait(sem_t *sem)
 {
    int rc;
    while ((rc = sem_wait(sem)) && (rc = errno) == EINTR) ;
    return rc;
 }
 
 #else	/* MDB_USE_POSIX_MUTEX: */
 	/** Shared mutex/semaphore as the original is stored.
 	 *
 	 *	Not for copies.  Instead it can be assigned to an #mdb_mutexref_t.
 	 *	When mdb_mutexref_t is a pointer and mdb_mutex_t is not, then it
 	 *	is array[size 1] so it can be assigned to the pointer.
 	 */
 typedef pthread_mutex_t mdb_mutex_t[1];
 	/** Reference to an #mdb_mutex_t */
 typedef pthread_mutex_t *mdb_mutexref_t;
 	/** Lock the reader or writer mutex.
 	 *	Returns 0 or a code to give #mdb_mutex_failed(), as in #LOCK_MUTEX().
 	 */
 #define LOCK_MUTEX0(mutex)	pthread_mutex_lock(mutex)
 	/** Unlock the reader or writer mutex.
 	 */
 #define UNLOCK_MUTEX(mutex)	pthread_mutex_unlock(mutex)
 	/** Mark mutex-protected data as repaired, after death of previous owner.
 	 */
 #define mdb_mutex_consistent(mutex)	pthread_mutex_consistent(mutex)
 #endif	/* MDB_USE_POSIX_SEM */
 
 	/** Get the error code for the last failed system function.
 	 */
 #define	ErrCode()	errno
 
 	/** An abstraction for a file handle.
 	 *	On POSIX systems file handles are small integers. On Windows
 	 *	they're opaque pointers.
 	 */
 #define	HANDLE	int
 
 	/**	A value for an invalid file handle.
 	 *	Mainly used to initialize file variables and signify that they are
 	 *	unused.
 	 */
 #define INVALID_HANDLE_VALUE	(-1)
 
 	/** Get the size of a memory page for the system.
 	 *	This is the basic size that the platform's memory manager uses, and is
 	 *	fundamental to the use of memory-mapped files.
 	 */
 #define	GET_PAGESIZE(x)	((x) = sysconf(_SC_PAGE_SIZE))
 #endif
 
 #if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
 #define MNAME_LEN	32
 #else
 #define MNAME_LEN	(sizeof(pthread_mutex_t))
 #endif
 
 /** @} */
 
 #ifdef MDB_ROBUST_SUPPORTED
 	/** Lock mutex, handle any error, set rc = result.
 	 *	Return 0 on success, nonzero (not rc) on error.
 	 */
 #define LOCK_MUTEX(rc, env, mutex) \
 	(((rc) = LOCK_MUTEX0(mutex)) && \
 	 ((rc) = mdb_mutex_failed(env, mutex, rc)))
 static int mdb_mutex_failed(MDB_env *env, mdb_mutexref_t mutex, int rc);
 #else
 #define LOCK_MUTEX(rc, env, mutex) ((rc) = LOCK_MUTEX0(mutex))
 #define mdb_mutex_failed(env, mutex, rc) (rc)
 #endif
 
 #ifndef _WIN32
 /**	A flag for opening a file and requesting synchronous data writes.
  *	This is only used when writing a meta page. It's not strictly needed;
  *	we could just do a normal write and then immediately perform a flush.
  *	But if this flag is available it saves us an extra system call.
  *
  *	@note If O_DSYNC is undefined but exists in /usr/include,
  * preferably set some compiler flag to get the definition.
  */
 #ifndef MDB_DSYNC
 # ifdef O_DSYNC
 # define MDB_DSYNC	O_DSYNC
 # else
 # define MDB_DSYNC	O_SYNC
 # endif
 #endif
 #endif
 
 /** Function for flushing the data of a file. Define this to fsync
  *	if fdatasync() is not supported.
  */
 #ifndef MDB_FDATASYNC
 # define MDB_FDATASYNC	fdatasync
 #endif
 
 #ifndef MDB_MSYNC
 # define MDB_MSYNC(addr,len,flags)	msync(addr,len,flags)
 #endif
 
 #ifndef MS_SYNC
 #define	MS_SYNC	1
 #endif
 
 #ifndef MS_ASYNC
 #define	MS_ASYNC	0
 #endif
 
 	/** A page number in the database.
 	 *	Note that 64 bit page numbers are overkill, since pages themselves
 	 *	already represent 12-13 bits of addressable memory, and the OS will
 	 *	always limit applications to a maximum of 63 bits of address space.
 	 *
 	 *	@note In the #MDB_node structure, we only store 48 bits of this value,
 	 *	which thus limits us to only 60 bits of addressable data.
 	 */
 typedef MDB_ID	pgno_t;
 
 	/** A transaction ID.
 	 *	See struct MDB_txn.mt_txnid for details.
 	 */
 typedef MDB_ID	txnid_t;
 
 /** @defgroup debug	Debug Macros
  *	@{
  */
 #ifndef MDB_DEBUG
 	/**	Enable debug output.  Needs variable argument macros (a C99 feature).
 	 *	Set this to 1 for copious tracing. Set to 2 to add dumps of all IDLs
 	 *	read from and written to the database (used for free space management).
 	 */
 #define MDB_DEBUG 0
 #endif
 
 #if MDB_DEBUG
 static int mdb_debug;
 static txnid_t mdb_debug_start;
 
 	/**	Print a debug message with printf formatting.
 	 *	Requires double parenthesis around 2 or more args.
 	 */
 # define DPRINTF(args) ((void) ((mdb_debug) && DPRINTF0 args))
 # define DPRINTF0(fmt, ...) \
 	fprintf(stderr, "%s:%d " fmt "\n", mdb_func_, __LINE__, __VA_ARGS__)
 #else
 # define DPRINTF(args)	((void) 0)
 #endif
 	/**	Print a debug string.
 	 *	The string is printed literally, with no format processing.
 	 */
 #define DPUTS(arg)	DPRINTF(("%s", arg))
 	/** Debugging output value of a cursor DBI: Negative in a sub-cursor. */
 #define DDBI(mc) \
 	(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
 /** @} */
 
 	/**	@brief The maximum size of a database page.
 	 *
 	 *	It is 32k or 64k, since value-PAGEBASE must fit in
 	 *	#MDB_page.%mp_upper.
 	 *
 	 *	LMDB will use database pages < OS pages if needed.
 	 *	That causes more I/O in write transactions: The OS must
 	 *	know (read) the whole page before writing a partial page.
 	 *
 	 *	Note that we don't currently support Huge pages. On Linux,
 	 *	regular data files cannot use Huge pages, and in general
 	 *	Huge pages aren't actually pageable. We rely on the OS
 	 *	demand-pager to read our data and page it out when memory
 	 *	pressure from other processes is high. So until OSs have
 	 *	actual paging support for Huge pages, they're not viable.
 	 */
 #define MAX_PAGESIZE	 (PAGEBASE ? 0x10000 : 0x8000)
 
 	/** The minimum number of keys required in a database page.
 	 *	Setting this to a larger value will place a smaller bound on the
 	 *	maximum size of a data item. Data items larger than this size will
 	 *	be pushed into overflow pages instead of being stored directly in
 	 *	the B-tree node. This value used to default to 4. With a page size
 	 *	of 4096 bytes that meant that any item larger than 1024 bytes would
 	 *	go into an overflow page. That also meant that on average 2-3KB of
 	 *	each overflow page was wasted space. The value cannot be lower than
 	 *	2 because then there would no longer be a tree structure. With this
 	 *	value, items larger than 2KB will go into overflow pages, and on
 	 *	average only 1KB will be wasted.
 	 */
 #define MDB_MINKEYS	 2
 
 	/**	A stamp that identifies a file as an LMDB file.
 	 *	There's nothing special about this value other than that it is easily
 	 *	recognizable, and it will reflect any byte order mismatches.
 	 */
 #define MDB_MAGIC	 0xBEEFC0DE
 
 	/**	The version number for a database's datafile format. */
 #define MDB_DATA_VERSION	 ((MDB_DEVEL) ? 999 : 1)
 	/**	The version number for a database's lockfile format. */
 #define MDB_LOCK_VERSION	 1
 
 	/**	@brief The max size of a key we can write, or 0 for computed max.
 	 *
 	 *	This macro should normally be left alone or set to 0.
 	 *	Note that a database with big keys or dupsort data cannot be
 	 *	reliably modified by a liblmdb which uses a smaller max.
 	 *	The default is 511 for backwards compat, or 0 when #MDB_DEVEL.
 	 *
 	 *	Other values are allowed, for backwards compat.  However:
 	 *	A value bigger than the computed max can break if you do not
 	 *	know what you are doing, and liblmdb <= 0.9.10 can break when
 	 *	modifying a DB with keys/dupsort data bigger than its max.
 	 *
 	 *	Data items in an #MDB_DUPSORT database are also limited to
 	 *	this size, since they're actually keys of a sub-DB.  Keys and
 	 *	#MDB_DUPSORT data items must fit on a node in a regular page.
 	 */
 #ifndef MDB_MAXKEYSIZE
 #define MDB_MAXKEYSIZE	 ((MDB_DEVEL) ? 0 : 511)
 #endif
 
 	/**	The maximum size of a key we can write to the environment. */
 #if MDB_MAXKEYSIZE
 #define ENV_MAXKEY(env)	(MDB_MAXKEYSIZE)
 #else
 #define ENV_MAXKEY(env)	((env)->me_maxkey)
 #endif
 
 	/**	@brief The maximum size of a data item.
 	 *
 	 *	We only store a 32 bit value for node sizes.
 	 */
 #define MAXDATASIZE	0xffffffffUL
 
 #if MDB_DEBUG
 	/**	Key size which fits in a #DKBUF.
 	 *	@ingroup debug
 	 */
 #define DKBUF_MAXKEYSIZE ((MDB_MAXKEYSIZE) > 0 ? (MDB_MAXKEYSIZE) : 511)
 	/**	A key buffer.
 	 *	@ingroup debug
 	 *	This is used for printing a hex dump of a key's contents.
 	 */
 #define DKBUF	char kbuf[DKBUF_MAXKEYSIZE*2+1]
 	/**	Display a key in hex.
 	 *	@ingroup debug
 	 *	Invoke a function to display a key in hex.
 	 */
 #define	DKEY(x)	mdb_dkey(x, kbuf)
 #else
 #define	DKBUF
 #define DKEY(x)	0
 #endif
 
 	/** An invalid page number.
 	 *	Mainly used to denote an empty tree.
 	 */
 #define P_INVALID	 (~(pgno_t)0)
 
 	/** Test if the flags \b f are set in a flag word \b w. */
 #define F_ISSET(w, f)	 (((w) & (f)) == (f))
 
 	/** Round \b n up to an even number. */
 #define EVEN(n)		(((n) + 1U) & -2) /* sign-extending -2 to match n+1U */
 
 	/**	Used for offsets within a single page.
 	 *	Since memory pages are typically 4 or 8KB in size, 12-13 bits,
 	 *	this is plenty.
 	 */
 typedef uint16_t	 indx_t;
 
 	/**	Default size of memory map.
 	 *	This is certainly too small for any actual applications. Apps should always set
 	 *	the size explicitly using #mdb_env_set_mapsize().
 	 */
 #define DEFAULT_MAPSIZE	1048576
 
 /**	@defgroup readers	Reader Lock Table
  *	Readers don't acquire any locks for their data access. Instead, they
  *	simply record their transaction ID in the reader table. The reader
  *	mutex is needed just to find an empty slot in the reader table. The
  *	slot's address is saved in thread-specific data so that subsequent read
  *	transactions started by the same thread need no further locking to proceed.
  *
  *	If #MDB_NOTLS is set, the slot address is not saved in thread-specific data.
  *
  *	No reader table is used if the database is on a read-only filesystem, or
  *	if #MDB_NOLOCK is set.
  *
  *	Since the database uses multi-version concurrency control, readers don't
  *	actually need any locking. This table is used to keep track of which
  *	readers are using data from which old transactions, so that we'll know
  *	when a particular old transaction is no longer in use. Old transactions
  *	that have discarded any data pages can then have those pages reclaimed
  *	for use by a later write transaction.
  *
  *	The lock table is constructed such that reader slots are aligned with the
  *	processor's cache line size. Any slot is only ever used by one thread.
  *	This alignment guarantees that there will be no contention or cache
  *	thrashing as threads update their own slot info, and also eliminates
  *	any need for locking when accessing a slot.
  *
  *	A writer thread will scan every slot in the table to determine the oldest
  *	outstanding reader transaction. Any freed pages older than this will be
  *	reclaimed by the writer. The writer doesn't use any locks when scanning
  *	this table. This means that there's no guarantee that the writer will
  *	see the most up-to-date reader info, but that's not required for correct
  *	operation - all we need is to know the upper bound on the oldest reader,
  *	we don't care at all about the newest reader. So the only consequence of
  *	reading stale information here is that old pages might hang around a
  *	while longer before being reclaimed. That's actually good anyway, because
  *	the longer we delay reclaiming old pages, the more likely it is that a
  *	string of contiguous pages can be found after coalescing old pages from
  *	many old transactions together.
  *	@{
  */
 	/**	Number of slots in the reader table.
 	 *	This value was chosen somewhat arbitrarily. 126 readers plus a
 	 *	couple mutexes fit exactly into 8KB on my development machine.
 	 *	Applications should set the table size using #mdb_env_set_maxreaders().
 	 */
 #define DEFAULT_READERS	126
 
 	/**	The size of a CPU cache line in bytes. We want our lock structures
 	 *	aligned to this size to avoid false cache line sharing in the
 	 *	lock table.
 	 *	This value works for most CPUs. For Itanium this should be 128.
 	 */
 #ifndef CACHELINE
 #define CACHELINE	64
 #endif
 
 	/**	The information we store in a single slot of the reader table.
 	 *	In addition to a transaction ID, we also record the process and
 	 *	thread ID that owns a slot, so that we can detect stale information,
 	 *	e.g. threads or processes that went away without cleaning up.
 	 *	@note We currently don't check for stale records. We simply re-init
 	 *	the table when we know that we're the only process opening the
 	 *	lock file.
 	 */
 typedef struct MDB_rxbody {
 	/**	Current Transaction ID when this transaction began, or (txnid_t)-1.
 	 *	Multiple readers that start at the same time will probably have the
 	 *	same ID here. Again, it's not important to exclude them from
 	 *	anything; all we need to know is which version of the DB they
 	 *	started from so we can avoid overwriting any data used in that
 	 *	particular version.
 	 */
 	volatile txnid_t		mrb_txnid;
 	/** The process ID of the process owning this reader txn. */
 	volatile MDB_PID_T	mrb_pid;
 	/** The thread ID of the thread owning this txn. */
 	volatile MDB_THR_T	mrb_tid;
 } MDB_rxbody;
 
 	/** The actual reader record, with cacheline padding. */
 typedef struct MDB_reader {
 	union {
 		MDB_rxbody mrx;
 		/** shorthand for mrb_txnid */
 #define	mr_txnid	mru.mrx.mrb_txnid
 #define	mr_pid	mru.mrx.mrb_pid
 #define	mr_tid	mru.mrx.mrb_tid
 		/** cache line alignment */
 		char pad[(sizeof(MDB_rxbody)+CACHELINE-1) & ~(CACHELINE-1)];
 	} mru;
 } MDB_reader;
 
 	/** The header for the reader table.
 	 *	The table resides in a memory-mapped file. (This is a different file
 	 *	than is used for the main database.)
 	 *
 	 *	For POSIX the actual mutexes reside in the shared memory of this
 	 *	mapped file. On Windows, mutexes are named objects allocated by the
 	 *	kernel; we store the mutex names in this mapped file so that other
 	 *	processes can grab them. This same approach is also used on
 	 *	MacOSX/Darwin (using named semaphores) since MacOSX doesn't support
 	 *	process-shared POSIX mutexes. For these cases where a named object
 	 *	is used, the object name is derived from a 64 bit FNV hash of the
 	 *	environment pathname. As such, naming collisions are extremely
 	 *	unlikely. If a collision occurs, the results are unpredictable.
 	 */
 typedef struct MDB_txbody {
 		/** Stamp identifying this as an LMDB file. It must be set
 		 *	to #MDB_MAGIC. */
 	uint32_t	mtb_magic;
 		/** Format of this lock file. Must be set to #MDB_LOCK_FORMAT. */
 	uint32_t	mtb_format;
 #if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
 	char	mtb_rmname[MNAME_LEN];
 #else
 		/** Mutex protecting access to this table.
 		 *	This is the reader table lock used with LOCK_MUTEX().
 		 */
 	mdb_mutex_t	mtb_rmutex;
 #endif
 		/**	The ID of the last transaction committed to the database.
 		 *	This is recorded here only for convenience; the value can always
 		 *	be determined by reading the main database meta pages.
 		 */
 	volatile txnid_t		mtb_txnid;
 		/** The number of slots that have been used in the reader table.
 		 *	This always records the maximum count, it is not decremented
 		 *	when readers release their slots.
 		 */
 	volatile unsigned	mtb_numreaders;
 } MDB_txbody;
 
 	/** The actual reader table definition. */
 typedef struct MDB_txninfo {
 	union {
 		MDB_txbody mtb;
 #define mti_magic	mt1.mtb.mtb_magic
 #define mti_format	mt1.mtb.mtb_format
 #define mti_rmutex	mt1.mtb.mtb_rmutex
 #define mti_rmname	mt1.mtb.mtb_rmname
 #define mti_txnid	mt1.mtb.mtb_txnid
 #define mti_numreaders	mt1.mtb.mtb_numreaders
 		char pad[(sizeof(MDB_txbody)+CACHELINE-1) & ~(CACHELINE-1)];
 	} mt1;
 	union {
 #if defined(_WIN32) || defined(MDB_USE_POSIX_SEM)
 		char mt2_wmname[MNAME_LEN];
 #define	mti_wmname	mt2.mt2_wmname
 #else
 		mdb_mutex_t	mt2_wmutex;
 #define mti_wmutex	mt2.mt2_wmutex
 #endif
 		char pad[(MNAME_LEN+CACHELINE-1) & ~(CACHELINE-1)];
 	} mt2;
 	MDB_reader	mti_readers[1];
 } MDB_txninfo;
 
 	/** Lockfile format signature: version, features and field layout */
 #define MDB_LOCK_FORMAT \
 	((uint32_t) \
 	 ((MDB_LOCK_VERSION) \
 	  /* Flags which describe functionality */ \
 	  + (((MDB_PIDLOCK) != 0) << 16)))
 /** @} */
 
 /** Common header for all page types. The page type depends on #mp_flags.
  *
  * #P_BRANCH and #P_LEAF pages have unsorted '#MDB_node's at the end, with
  * sorted #mp_ptrs[] entries referring to them. Exception: #P_LEAF2 pages
  * omit mp_ptrs and pack sorted #MDB_DUPFIXED values after the page header.
  *
  * #P_OVERFLOW records occupy one or more contiguous pages where only the
  * first has a page header. They hold the real data of #F_BIGDATA nodes.
  *
  * #P_SUBP sub-pages are small leaf "pages" with duplicate data.
  * A node with flag #F_DUPDATA but not #F_SUBDATA contains a sub-page.
  * (Duplicate data can also go in sub-databases, which use normal pages.)
  *
  * #P_META pages contain #MDB_meta, the start point of an LMDB snapshot.
  *
  * Each non-metapage up to #MDB_meta.%mm_last_pg is reachable exactly once
  * in the snapshot: Either used by a database or listed in a freeDB record.
  */
 typedef struct MDB_page {
 #define	mp_pgno	mp_p.p_pgno
 #define	mp_next	mp_p.p_next
 	union {
 		pgno_t		p_pgno;	/**< page number */
 		struct MDB_page *p_next; /**< for in-memory list of freed pages */
 	} mp_p;
 	uint16_t	mp_pad;			/**< key size if this is a LEAF2 page */
 /**	@defgroup mdb_page	Page Flags
  *	@ingroup internal
  *	Flags for the page headers.
  *	@{
  */
 #define	P_BRANCH	 0x01		/**< branch page */
 #define	P_LEAF		 0x02		/**< leaf page */
 #define	P_OVERFLOW	 0x04		/**< overflow page */
 #define	P_META		 0x08		/**< meta page */
 #define	P_DIRTY		 0x10		/**< dirty page, also set for #P_SUBP pages */
 #define	P_LEAF2		 0x20		/**< for #MDB_DUPFIXED records */
 #define	P_SUBP		 0x40		/**< for #MDB_DUPSORT sub-pages */
 #define	P_LOOSE		 0x4000		/**< page was dirtied then freed, can be reused */
 #define	P_KEEP		 0x8000		/**< leave this page alone during spill */
 /** @} */
 	uint16_t	mp_flags;		/**< @ref mdb_page */
 #define mp_lower	mp_pb.pb.pb_lower
 #define mp_upper	mp_pb.pb.pb_upper
 #define mp_pages	mp_pb.pb_pages
 	union {
 		struct {
 			indx_t		pb_lower;		/**< lower bound of free space */
 			indx_t		pb_upper;		/**< upper bound of free space */
 		} pb;
 		uint32_t	pb_pages;	/**< number of overflow pages */
 	} mp_pb;
 	indx_t		mp_ptrs[0];		/**< dynamic size */
 } MDB_page;
 
 /** Alternate page header, for 2-byte aligned access */
 typedef struct MDB_page2 {
 	uint16_t	mp2_p[sizeof(pgno_t)/2];
 	uint16_t	mp2_pad;
 	uint16_t	mp2_flags;
 	indx_t		mp2_lower;
 	indx_t		mp2_upper;
 	indx_t		mp2_ptrs[0];
 } MDB_page2;
 
 #define MP_PGNO(p)	(((MDB_page2 *)(void *)(p))->mp2_p)
 #define MP_PAD(p)	(((MDB_page2 *)(void *)(p))->mp2_pad)
 #define MP_FLAGS(p)	(((MDB_page2 *)(void *)(p))->mp2_flags)
 #define MP_LOWER(p)	(((MDB_page2 *)(void *)(p))->mp2_lower)
 #define MP_UPPER(p)	(((MDB_page2 *)(void *)(p))->mp2_upper)
 #define MP_PTRS(p)	(((MDB_page2 *)(void *)(p))->mp2_ptrs)
 
 	/** Size of the page header, excluding dynamic data at the end */
 #define PAGEHDRSZ	 ((unsigned) offsetof(MDB_page, mp_ptrs))
 
 	/** Address of first usable data byte in a page, after the header */
 #define METADATA(p)	 ((void *)((char *)(p) + PAGEHDRSZ))
 
 	/** ITS#7713, change PAGEBASE to handle 65536 byte pages */
 #define	PAGEBASE	((MDB_DEVEL) ? PAGEHDRSZ : 0)
 
 	/** Number of nodes on a page */
 #define NUMKEYS(p)	 ((MP_LOWER(p) - (PAGEHDRSZ-PAGEBASE)) >> 1)
 
 	/** The amount of space remaining in the page */
 #define SIZELEFT(p)	 (indx_t)(MP_UPPER(p) - MP_LOWER(p))
 
 	/** The percentage of space used in the page, in tenths of a percent. */
 #define PAGEFILL(env, p) (1000L * ((env)->me_psize - PAGEHDRSZ - SIZELEFT(p)) / \
 				((env)->me_psize - PAGEHDRSZ))
 	/** The minimum page fill factor, in tenths of a percent.
 	 *	Pages emptier than this are candidates for merging.
 	 */
 #define FILL_THRESHOLD	 250
 
 	/** Test if a page is a leaf page */
 #define IS_LEAF(p)	 F_ISSET(MP_FLAGS(p), P_LEAF)
 	/** Test if a page is a LEAF2 page */
 #define IS_LEAF2(p)	 F_ISSET(MP_FLAGS(p), P_LEAF2)
 	/** Test if a page is a branch page */
 #define IS_BRANCH(p)	 F_ISSET(MP_FLAGS(p), P_BRANCH)
 	/** Test if a page is an overflow page */
 #define IS_OVERFLOW(p)	 F_ISSET(MP_FLAGS(p), P_OVERFLOW)
 	/** Test if a page is a sub page */
 #define IS_SUBP(p)	 F_ISSET(MP_FLAGS(p), P_SUBP)
 
 	/** The number of overflow pages needed to store the given size. */
 #define OVPAGES(size, psize)	((PAGEHDRSZ-1 + (size)) / (psize) + 1)
 
 	/** Link in #MDB_txn.%mt_loose_pgs list.
 	 *  Kept outside the page header, which is needed when reusing the page.
 	 */
 #define NEXT_LOOSE_PAGE(p)		(*(MDB_page **)((p) + 2))
 
 	/** Header for a single key/data pair within a page.
 	 * Used in pages of type #P_BRANCH and #P_LEAF without #P_LEAF2.
 	 * We guarantee 2-byte alignment for 'MDB_node's.
 	 *
 	 * #mn_lo and #mn_hi are used for data size on leaf nodes, and for child
 	 * pgno on branch nodes.  On 64 bit platforms, #mn_flags is also used
 	 * for pgno.  (Branch nodes have no flags).  Lo and hi are in host byte
 	 * order in case some accesses can be optimized to 32-bit word access.
 	 *
 	 * Leaf node flags describe node contents.  #F_BIGDATA says the node's
 	 * data part is the page number of an overflow page with actual data.
 	 * #F_DUPDATA and #F_SUBDATA can be combined giving duplicate data in
 	 * a sub-page/sub-database, and named databases (just #F_SUBDATA).
 	 */
 typedef struct MDB_node {
 	/** part of data size or pgno
 	 *	@{ */
 #if BYTE_ORDER == LITTLE_ENDIAN
 	unsigned short	mn_lo, mn_hi;
 #else
 	unsigned short	mn_hi, mn_lo;
 #endif
 	/** @} */
 /** @defgroup mdb_node Node Flags
  *	@ingroup internal
  *	Flags for node headers.
  *	@{
  */
 #define F_BIGDATA	 0x01			/**< data put on overflow page */
 #define F_SUBDATA	 0x02			/**< data is a sub-database */
 #define F_DUPDATA	 0x04			/**< data has duplicates */
 
 /** valid flags for #mdb_node_add() */
 #define	NODE_ADD_FLAGS	(F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
 
 /** @} */
 	unsigned short	mn_flags;		/**< @ref mdb_node */
 	unsigned short	mn_ksize;		/**< key size */
 	char		mn_data[1];			/**< key and data are appended here */
 } MDB_node;
 
 	/** Size of the node header, excluding dynamic data at the end */
 #define NODESIZE	 offsetof(MDB_node, mn_data)
 
 	/** Bit position of top word in page number, for shifting mn_flags */
 #define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)
 
 	/** Size of a node in a branch page with a given key.
 	 *	This is just the node header plus the key, there is no data.
 	 */
 #define INDXSIZE(k)	 (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
 
 	/** Size of a node in a leaf page with a given key and data.
 	 *	This is node header plus key plus data size.
 	 */
 #define LEAFSIZE(k, d)	 (NODESIZE + (k)->mv_size + (d)->mv_size)
 
 	/** Address of node \b i in page \b p */
 #define NODEPTR(p, i)	 ((MDB_node *)((char *)(p) + MP_PTRS(p)[i] + PAGEBASE))
 
 	/** Address of the key for the node */
 #define NODEKEY(node)	 (void *)((node)->mn_data)
 
 	/** Address of the data for a node */
 #define NODEDATA(node)	 (void *)((char *)(node)->mn_data + (node)->mn_ksize)
 
 	/** Get the page number pointed to by a branch node */
 #define NODEPGNO(node) \
 	((node)->mn_lo | ((pgno_t) (node)->mn_hi << 16) | \
 	 (PGNO_TOPWORD ? ((pgno_t) (node)->mn_flags << PGNO_TOPWORD) : 0))
 	/** Set the page number in a branch node */
 #define SETPGNO(node,pgno)	do { \
 	(node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
 	if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
 
 	/** Get the size of the data in a leaf node */
 #define NODEDSZ(node)	 ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
 	/** Set the size of the data for a leaf node */
 #define SETDSZ(node,size)	do { \
 	(node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
 	/** The size of a key in a node */
 #define NODEKSZ(node)	 ((node)->mn_ksize)
 
 	/** Copy a page number from src to dst */
 #ifdef MISALIGNED_OK
 #define COPY_PGNO(dst,src)	dst = src
 #undef MP_PGNO
 #define MP_PGNO(p)	((p)->mp_pgno)
 #else
 #if SIZE_MAX > 4294967295UL
 #define COPY_PGNO(dst,src)	do { \
 	unsigned short *s, *d;	\
 	s = (unsigned short *)&(src);	\
 	d = (unsigned short *)&(dst);	\
 	*d++ = *s++;	\
 	*d++ = *s++;	\
 	*d++ = *s++;	\
 	*d = *s;	\
 } while (0)
 #else
 #define COPY_PGNO(dst,src)	do { \
 	unsigned short *s, *d;	\
 	s = (unsigned short *)&(src);	\
 	d = (unsigned short *)&(dst);	\
 	*d++ = *s++;	\
 	*d = *s;	\
 } while (0)
 #endif
 #endif
 	/** The address of a key in a LEAF2 page.
 	 *	LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
 	 *	There are no node headers, keys are stored contiguously.
 	 */
 #define LEAF2KEY(p, i, ks)	((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
 
 	/** Set the \b node's key into \b keyptr, if requested. */
 #define MDB_GET_KEY(node, keyptr)	{ if ((keyptr) != NULL) { \
 	(keyptr)->mv_size = NODEKSZ(node); (keyptr)->mv_data = NODEKEY(node); } }
 
 	/** Set the \b node's key into \b key. */
 #define MDB_GET_KEY2(node, key)	{ key.mv_size = NODEKSZ(node); key.mv_data = NODEKEY(node); }
 
 	/** Information about a single database in the environment. */
 typedef struct MDB_db {
 	uint32_t	md_pad;		/**< also ksize for LEAF2 pages */
 	uint16_t	md_flags;	/**< @ref mdb_dbi_open */
 	uint16_t	md_depth;	/**< depth of this tree */
 	pgno_t		md_branch_pages;	/**< number of internal pages */
 	pgno_t		md_leaf_pages;		/**< number of leaf pages */
 	pgno_t		md_overflow_pages;	/**< number of overflow pages */
 	size_t		md_entries;		/**< number of data items */
 	pgno_t		md_root;		/**< the root page of this tree */
 } MDB_db;
 
 #define MDB_VALID	0x8000		/**< DB handle is valid, for me_dbflags */
 #define PERSISTENT_FLAGS	(0xffff & ~(MDB_VALID))
 	/** #mdb_dbi_open() flags */
 #define VALID_FLAGS	(MDB_REVERSEKEY|MDB_DUPSORT|MDB_INTEGERKEY|MDB_DUPFIXED|\
 	MDB_INTEGERDUP|MDB_REVERSEDUP|MDB_CREATE)
 
 	/** Handle for the DB used to track free pages. */
 #define	FREE_DBI	0
 	/** Handle for the default DB. */
 #define	MAIN_DBI	1
 	/** Number of DBs in metapage (free and main) - also hardcoded elsewhere */
 #define CORE_DBS	2
 
 	/** Number of meta pages - also hardcoded elsewhere */
 #define NUM_METAS	2
 
 	/** Meta page content.
 	 *	A meta page is the start point for accessing a database snapshot.
 	 *	Pages 0-1 are meta pages. Transaction N writes meta page #(N % 2).
 	 */
 typedef struct MDB_meta {
 		/** Stamp identifying this as an LMDB file. It must be set
 		 *	to #MDB_MAGIC. */
 	uint32_t	mm_magic;
 		/** Version number of this file. Must be set to #MDB_DATA_VERSION. */
 	uint32_t	mm_version;
 	void		*mm_address;		/**< address for fixed mapping */
 	size_t		mm_mapsize;			/**< size of mmap region */
 	MDB_db		mm_dbs[CORE_DBS];	/**< first is free space, 2nd is main db */
 	/** The size of pages used in this DB */
 #define	mm_psize	mm_dbs[FREE_DBI].md_pad
 	/** Any persistent environment flags. @ref mdb_env */
 #define	mm_flags	mm_dbs[FREE_DBI].md_flags
 	/** Last used page in the datafile.
 	 *	Actually the file may be shorter if the freeDB lists the final pages.
 	 */
 	pgno_t		mm_last_pg;
 	volatile txnid_t	mm_txnid;	/**< txnid that committed this page */
 } MDB_meta;
 
 	/** Buffer for a stack-allocated meta page.
 	 *	The members define size and alignment, and silence type
 	 *	aliasing warnings.  They are not used directly; that could
 	 *	mean incorrectly using several union members in parallel.
 	 */
 typedef union MDB_metabuf {
 	MDB_page	mb_page;
 	struct {
 		char		mm_pad[PAGEHDRSZ];
 		MDB_meta	mm_meta;
 	} mb_metabuf;
 } MDB_metabuf;
 
 	/** Auxiliary DB info.
 	 *	The information here is mostly static/read-only. There is
 	 *	only a single copy of this record in the environment.
 	 */
 typedef struct MDB_dbx {
 	MDB_val		md_name;		/**< name of the database */
 	MDB_cmp_func	*md_cmp;	/**< function for comparing keys */
 	MDB_cmp_func	*md_dcmp;	/**< function for comparing data items */
 	MDB_rel_func	*md_rel;	/**< user relocate function */
 	void		*md_relctx;		/**< user-provided context for md_rel */
 } MDB_dbx;
 
 	/** A database transaction.
 	 *	Every operation requires a transaction handle.
 	 */
 struct MDB_txn {
 	MDB_txn		*mt_parent;		/**< parent of a nested txn */
 	/** Nested txn under this txn, set together with flag #MDB_TXN_HAS_CHILD */
 	MDB_txn		*mt_child;
 	pgno_t		mt_next_pgno;	/**< next unallocated page */
 	/** The ID of this transaction. IDs are integers incrementing from 1.
 	 *	Only committed write transactions increment the ID. If a transaction
 	 *	aborts, the ID may be re-used by the next writer.
 	 */
 	txnid_t		mt_txnid;
 	MDB_env		*mt_env;		/**< the DB environment */
 	/** The list of pages that became unused during this transaction.
 	 */
 	MDB_IDL		mt_free_pgs;
 	/** The list of loose pages that became unused and may be reused
 	 *	in this transaction, linked through #NEXT_LOOSE_PAGE(page).
 	 */
 	MDB_page	*mt_loose_pgs;
 	/** Number of loose pages (#mt_loose_pgs) */
 	int			mt_loose_count;
 	/** The sorted list of dirty pages we temporarily wrote to disk
 	 *	because the dirty list was full. page numbers in here are
 	 *	shifted left by 1, deleted slots have the LSB set.
 	 */
 	MDB_IDL		mt_spill_pgs;
 	union {
 		/** For write txns: Modified pages. Sorted when not MDB_WRITEMAP. */
 		MDB_ID2L	dirty_list;
 		/** For read txns: This thread/txn's reader table slot, or NULL. */
 		MDB_reader	*reader;
 	} mt_u;
 	/** Array of records for each DB known in the environment. */
 	MDB_dbx		*mt_dbxs;
 	/** Array of MDB_db records for each known DB */
 	MDB_db		*mt_dbs;
 	/** Array of sequence numbers for each DB handle */
 	unsigned int	*mt_dbiseqs;
 /** @defgroup mt_dbflag	Transaction DB Flags
  *	@ingroup internal
  * @{
  */
 #define DB_DIRTY	0x01		/**< DB was written in this txn */
 #define DB_STALE	0x02		/**< Named-DB record is older than txnID */
 #define DB_NEW		0x04		/**< Named-DB handle opened in this txn */
 #define DB_VALID	0x08		/**< DB handle is valid, see also #MDB_VALID */
 #define DB_USRVALID	0x10		/**< As #DB_VALID, but not set for #FREE_DBI */
 #define DB_DUPDATA	0x20		/**< DB is #MDB_DUPSORT data */
 /** @} */
 	/** In write txns, array of cursors for each DB */
 	MDB_cursor	**mt_cursors;
 	/** Array of flags for each DB */
 	unsigned char	*mt_dbflags;
 	/**	Number of DB records in use, or 0 when the txn is finished.
 	 *	This number only ever increments until the txn finishes; we
 	 *	don't decrement it when individual DB handles are closed.
 	 */
 	MDB_dbi		mt_numdbs;
 
 /** @defgroup mdb_txn	Transaction Flags
  *	@ingroup internal
  *	@{
  */
 	/** #mdb_txn_begin() flags */
 #define MDB_TXN_BEGIN_FLAGS	MDB_RDONLY
 #define MDB_TXN_RDONLY		MDB_RDONLY	/**< read-only transaction */
 	/* internal txn flags */
 #define MDB_TXN_WRITEMAP	MDB_WRITEMAP	/**< copy of #MDB_env flag in writers */
 #define MDB_TXN_FINISHED	0x01		/**< txn is finished or never began */
 #define MDB_TXN_ERROR		0x02		/**< txn is unusable after an error */
 #define MDB_TXN_DIRTY		0x04		/**< must write, even if dirty list is empty */
 #define MDB_TXN_SPILLS		0x08		/**< txn or a parent has spilled pages */
 #define MDB_TXN_HAS_CHILD	0x10		/**< txn has an #MDB_txn.%mt_child */
 	/** most operations on the txn are currently illegal */
 #define MDB_TXN_BLOCKED		(MDB_TXN_FINISHED|MDB_TXN_ERROR|MDB_TXN_HAS_CHILD)
 /** @} */
 	unsigned int	mt_flags;		/**< @ref mdb_txn */
 	/** #dirty_list room: Array size - \#dirty pages visible to this txn.
 	 *	Includes ancestor txns' dirty pages not hidden by other txns'
 	 *	dirty/spilled pages. Thus commit(nested txn) has room to merge
 	 *	dirty_list into mt_parent after freeing hidden mt_parent pages.
 	 */
 	unsigned int	mt_dirty_room;
 };
 
 /** Enough space for 2^32 nodes with minimum of 2 keys per node. I.e., plenty.
  * At 4 keys per node, enough for 2^64 nodes, so there's probably no need to
  * raise this on a 64 bit machine.
  */
 #define CURSOR_STACK		 32
 
 struct MDB_xcursor;
 
 	/** Cursors are used for all DB operations.
 	 *	A cursor holds a path of (page pointer, key index) from the DB
 	 *	root to a position in the DB, plus other state. #MDB_DUPSORT
 	 *	cursors include an xcursor to the current data item. Write txns
 	 *	track their cursors and keep them up to date when data moves.
 	 *	Exception: An xcursor's pointer to a #P_SUBP page can be stale.
 	 *	(A node with #F_DUPDATA but no #F_SUBDATA contains a subpage).
 	 */
 struct MDB_cursor {
 	/** Next cursor on this DB in this txn */
 	MDB_cursor	*mc_next;
 	/** Backup of the original cursor if this cursor is a shadow */
 	MDB_cursor	*mc_backup;
 	/** Context used for databases with #MDB_DUPSORT, otherwise NULL */
 	struct MDB_xcursor	*mc_xcursor;
 	/** The transaction that owns this cursor */
 	MDB_txn		*mc_txn;
 	/** The database handle this cursor operates on */
 	MDB_dbi		mc_dbi;
 	/** The database record for this cursor */
 	MDB_db		*mc_db;
 	/** The database auxiliary record for this cursor */
 	MDB_dbx		*mc_dbx;
 	/** The @ref mt_dbflag for this database */
 	unsigned char	*mc_dbflag;
 	unsigned short 	mc_snum;	/**< number of pushed pages */
 	unsigned short	mc_top;		/**< index of top page, normally mc_snum-1 */
 /** @defgroup mdb_cursor	Cursor Flags
  *	@ingroup internal
  *	Cursor state flags.
  *	@{
  */
 #define C_INITIALIZED	0x01	/**< cursor has been initialized and is valid */
 #define C_EOF	0x02			/**< No more data */
 #define C_SUB	0x04			/**< Cursor is a sub-cursor */
 #define C_DEL	0x08			/**< last op was a cursor_del */
 #define C_UNTRACK	0x40		/**< Un-track cursor when closing */
 /** @} */
 	unsigned int	mc_flags;	/**< @ref mdb_cursor */
 	MDB_page	*mc_pg[CURSOR_STACK];	/**< stack of pushed pages */
 	indx_t		mc_ki[CURSOR_STACK];	/**< stack of page indices */
 };
 
 	/** Context for sorted-dup records.
 	 *	We could have gone to a fully recursive design, with arbitrarily
 	 *	deep nesting of sub-databases. But for now we only handle these
 	 *	levels - main DB, optional sub-DB, sorted-duplicate DB.
 	 */
 typedef struct MDB_xcursor {
 	/** A sub-cursor for traversing the Dup DB */
 	MDB_cursor mx_cursor;
 	/** The database record for this Dup DB */
 	MDB_db	mx_db;
 	/**	The auxiliary DB record for this Dup DB */
 	MDB_dbx	mx_dbx;
 	/** The @ref mt_dbflag for this Dup DB */
 	unsigned char mx_dbflag;
 } MDB_xcursor;
 
 	/** Check if there is an inited xcursor */
 #define XCURSOR_INITED(mc) \
 	((mc)->mc_xcursor && ((mc)->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
 
 	/** Update the xcursor's sub-page pointer, if any, in \b mc.  Needed
 	 *	when the node which contains the sub-page may have moved.  Called
 	 *	with leaf page \b mp = mc->mc_pg[\b top].
 	 */
 #define XCURSOR_REFRESH(mc, top, mp) do { \
 	MDB_page *xr_pg = (mp); \
 	MDB_node *xr_node; \
 	if (!XCURSOR_INITED(mc) || (mc)->mc_ki[top] >= NUMKEYS(xr_pg)) break; \
 	xr_node = NODEPTR(xr_pg, (mc)->mc_ki[top]); \
 	if ((xr_node->mn_flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA) \
 		(mc)->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(xr_node); \
 } while (0)
 
 	/** State of FreeDB old pages, stored in the MDB_env */
 typedef struct MDB_pgstate {
 	pgno_t		*mf_pghead;	/**< Reclaimed freeDB pages, or NULL before use */
 	txnid_t		mf_pglast;	/**< ID of last used record, or 0 if !mf_pghead */
 } MDB_pgstate;
 
 	/** The database environment. */
 struct MDB_env {
 	HANDLE		me_fd;		/**< The main data file */
 	HANDLE		me_lfd;		/**< The lock file */
 	HANDLE		me_mfd;		/**< For writing and syncing the meta pages */
 	/** Failed to update the meta page. Probably an I/O error. */
 #define	MDB_FATAL_ERROR	0x80000000U
 	/** Some fields are initialized. */
 #define	MDB_ENV_ACTIVE	0x20000000U
 	/** me_txkey is set */
 #define	MDB_ENV_TXKEY	0x10000000U
 	/** fdatasync is unreliable */
 #define	MDB_FSYNCONLY	0x08000000U
 	uint32_t 	me_flags;		/**< @ref mdb_env */
 	unsigned int	me_psize;	/**< DB page size, inited from me_os_psize */
 	unsigned int	me_os_psize;	/**< OS page size, from #GET_PAGESIZE */
 	unsigned int	me_maxreaders;	/**< size of the reader table */
 	/** Max #MDB_txninfo.%mti_numreaders of interest to #mdb_env_close() */
 	volatile int	me_close_readers;
 	MDB_dbi		me_numdbs;		/**< number of DBs opened */
 	MDB_dbi		me_maxdbs;		/**< size of the DB table */
 	MDB_PID_T	me_pid;		/**< process ID of this env */
 	char		*me_path;		/**< path to the DB files */
 	char		*me_map;		/**< the memory map of the data file */
 	MDB_txninfo	*me_txns;		/**< the memory map of the lock file or NULL */
 	MDB_meta	*me_metas[NUM_METAS];	/**< pointers to the two meta pages */
 	void		*me_pbuf;		/**< scratch area for DUPSORT put() */
 	MDB_txn		*me_txn;		/**< current write transaction */
 	MDB_txn		*me_txn0;		/**< prealloc'd write transaction */
 	size_t		me_mapsize;		/**< size of the data memory map */
 	off_t		me_size;		/**< current file size */
 	pgno_t		me_maxpg;		/**< me_mapsize / me_psize */
 	MDB_dbx		*me_dbxs;		/**< array of static DB info */
 	uint16_t	*me_dbflags;	/**< array of flags from MDB_db.md_flags */
 	unsigned int	*me_dbiseqs;	/**< array of dbi sequence numbers */
 	pthread_key_t	me_txkey;	/**< thread-key for readers */
 	txnid_t		me_pgoldest;	/**< ID of oldest reader last time we looked */
 	MDB_pgstate	me_pgstate;		/**< state of old pages from freeDB */
 #	define		me_pglast	me_pgstate.mf_pglast
 #	define		me_pghead	me_pgstate.mf_pghead
 	MDB_page	*me_dpages;		/**< list of malloc'd blocks for re-use */
 	/** IDL of pages that became unused in a write txn */
 	MDB_IDL		me_free_pgs;
 	/** ID2L of pages written during a write txn. Length MDB_IDL_UM_SIZE. */
 	MDB_ID2L	me_dirty_list;
 	/** Max number of freelist items that can fit in a single overflow page */
 	int			me_maxfree_1pg;
 	/** Max size of a node on a page */
 	unsigned int	me_nodemax;
 #if !(MDB_MAXKEYSIZE)
 	unsigned int	me_maxkey;	/**< max size of a key */
 #endif
 	int		me_live_reader;		/**< have liveness lock in reader table */
 #ifdef _WIN32
 	int		me_pidquery;		/**< Used in OpenProcess */
 #endif
 #ifdef MDB_USE_POSIX_MUTEX	/* Posix mutexes reside in shared mem */
 #	define		me_rmutex	me_txns->mti_rmutex /**< Shared reader lock */
 #	define		me_wmutex	me_txns->mti_wmutex /**< Shared writer lock */
 #else
 	mdb_mutex_t	me_rmutex;
 	mdb_mutex_t	me_wmutex;
 #endif
 	void		*me_userctx;	 /**< User-settable context */
 	MDB_assert_func *me_assert_func; /**< Callback for assertion failures */
 };
 
 	/** Nested transaction */
 typedef struct MDB_ntxn {
 	MDB_txn		mnt_txn;		/**< the transaction */
 	MDB_pgstate	mnt_pgstate;	/**< parent transaction's saved freestate */
 } MDB_ntxn;
 
 	/** max number of pages to commit in one writev() call */
 #define MDB_COMMIT_PAGES	 64
 #if defined(IOV_MAX) && IOV_MAX < MDB_COMMIT_PAGES
 #undef MDB_COMMIT_PAGES
 #define MDB_COMMIT_PAGES	IOV_MAX
 #endif
 
 	/** max bytes to write in one call */
 #define MAX_WRITE		(0x40000000U >> (sizeof(ssize_t) == 4))
 
 	/** Check \b txn and \b dbi arguments to a function */
 #define TXN_DBI_EXIST(txn, dbi, validity) \
 	((txn) && (dbi)<(txn)->mt_numdbs && ((txn)->mt_dbflags[dbi] & (validity)))
 
 	/** Check for misused \b dbi handles */
 #define TXN_DBI_CHANGED(txn, dbi) \
 	((txn)->mt_dbiseqs[dbi] != (txn)->mt_env->me_dbiseqs[dbi])
 
 static int  mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp);
 static int  mdb_page_new(MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp);
 static int  mdb_page_touch(MDB_cursor *mc);
 
 #define MDB_END_NAMES {"committed", "empty-commit", "abort", "reset", \
 	"reset-tmp", "fail-begin", "fail-beginchild"}
 enum {
 	/* mdb_txn_end operation number, for logging */
 	MDB_END_COMMITTED, MDB_END_EMPTY_COMMIT, MDB_END_ABORT, MDB_END_RESET,
 	MDB_END_RESET_TMP, MDB_END_FAIL_BEGIN, MDB_END_FAIL_BEGINCHILD
 };
 #define MDB_END_OPMASK	0x0F	/**< mask for #mdb_txn_end() operation number */
 #define MDB_END_UPDATE	0x10	/**< update env state (DBIs) */
 #define MDB_END_FREE	0x20	/**< free txn unless it is #MDB_env.%me_txn0 */
 #define MDB_END_SLOT MDB_NOTLS	/**< release any reader slot if #MDB_NOTLS */
 static void mdb_txn_end(MDB_txn *txn, unsigned mode);
 
 static int  mdb_page_get(MDB_cursor *mc, pgno_t pgno, MDB_page **mp, int *lvl);
 static int  mdb_page_search_root(MDB_cursor *mc,
 			    MDB_val *key, int modify);
 #define MDB_PS_MODIFY	1
 #define MDB_PS_ROOTONLY	2
 #define MDB_PS_FIRST	4
 #define MDB_PS_LAST		8
 static int  mdb_page_search(MDB_cursor *mc,
 			    MDB_val *key, int flags);
 static int	mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst);
 
 #define MDB_SPLIT_REPLACE	MDB_APPENDDUP	/**< newkey is not new */
 static int	mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
 				pgno_t newpgno, unsigned int nflags);
 
 static int  mdb_env_read_header(MDB_env *env, MDB_meta *meta);
 static MDB_meta *mdb_env_pick_meta(const MDB_env *env);
 static int  mdb_env_write_meta(MDB_txn *txn);
 #if defined(MDB_USE_POSIX_MUTEX) && !defined(MDB_ROBUST_SUPPORTED) /* Drop unused excl arg */
 # define mdb_env_close0(env, excl) mdb_env_close1(env)
 #endif
 static void mdb_env_close0(MDB_env *env, int excl);
 
 static MDB_node *mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp);
 static int  mdb_node_add(MDB_cursor *mc, indx_t indx,
 			    MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags);
 static void mdb_node_del(MDB_cursor *mc, int ksize);
 static void mdb_node_shrink(MDB_page *mp, indx_t indx);
 static int	mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst, int fromleft);
 static int  mdb_node_read(MDB_cursor *mc, MDB_node *leaf, MDB_val *data);
 static size_t	mdb_leaf_size(MDB_env *env, MDB_val *key, MDB_val *data);
 static size_t	mdb_branch_size(MDB_env *env, MDB_val *key);
 
 static int	mdb_rebalance(MDB_cursor *mc);
 static int	mdb_update_key(MDB_cursor *mc, MDB_val *key);
 
 static void	mdb_cursor_pop(MDB_cursor *mc);
 static int	mdb_cursor_push(MDB_cursor *mc, MDB_page *mp);
 
 static int	mdb_cursor_del0(MDB_cursor *mc);
 static int	mdb_del0(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data, unsigned flags);
 static int	mdb_cursor_sibling(MDB_cursor *mc, int move_right);
 static int	mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
 static int	mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op);
 static int	mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op,
 				int *exactp);
 static int	mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data);
 static int	mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data);
 
 static void	mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx);
 static void	mdb_xcursor_init0(MDB_cursor *mc);
 static void	mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node);
 static void	mdb_xcursor_init2(MDB_cursor *mc, MDB_xcursor *src_mx, int force);
 
 static int	mdb_drop0(MDB_cursor *mc, int subs);
 static void mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi);
 static int mdb_reader_check0(MDB_env *env, int rlocked, int *dead);
 
 /** @cond */
 static MDB_cmp_func	mdb_cmp_memn, mdb_cmp_memnr, mdb_cmp_int, mdb_cmp_cint, mdb_cmp_long;
 /** @endcond */
 
 /** Compare two items pointing at size_t's of unknown alignment. */
 #ifdef MISALIGNED_OK
 # define mdb_cmp_clong mdb_cmp_long
 #else
 # define mdb_cmp_clong mdb_cmp_cint
 #endif
 
 #ifdef _WIN32
 static SECURITY_DESCRIPTOR mdb_null_sd;
 static SECURITY_ATTRIBUTES mdb_all_sa;
 static int mdb_sec_inited;
 
 struct MDB_name;
 static int utf8_to_utf16(const char *src, struct MDB_name *dst, int xtra);
 #endif
 
 /** Return the library version info. */
 char * ESECT
 mdb_version(int *major, int *minor, int *patch)
 {
 	if (major) *major = MDB_VERSION_MAJOR;
 	if (minor) *minor = MDB_VERSION_MINOR;
 	if (patch) *patch = MDB_VERSION_PATCH;
 	return MDB_VERSION_STRING;
 }
 
 /** Table of descriptions for LMDB @ref errors */
 static char *const mdb_errstr[] = {
 	"MDB_KEYEXIST: Key/data pair already exists",
 	"MDB_NOTFOUND: No matching key/data pair found",
 	"MDB_PAGE_NOTFOUND: Requested page not found",
 	"MDB_CORRUPTED: Located page was wrong type",
 	"MDB_PANIC: Update of meta page failed or environment had fatal error",
 	"MDB_VERSION_MISMATCH: Database environment version mismatch",
 	"MDB_INVALID: File is not an LMDB file",
 	"MDB_MAP_FULL: Environment mapsize limit reached",
 	"MDB_DBS_FULL: Environment maxdbs limit reached",
 	"MDB_READERS_FULL: Environment maxreaders limit reached",
 	"MDB_TLS_FULL: Thread-local storage keys full - too many environments open",
 	"MDB_TXN_FULL: Transaction has too many dirty pages - transaction too big",
 	"MDB_CURSOR_FULL: Internal error - cursor stack limit reached",
 	"MDB_PAGE_FULL: Internal error - page has no more space",
 	"MDB_MAP_RESIZED: Database contents grew beyond environment mapsize",
 	"MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed",
 	"MDB_BAD_RSLOT: Invalid reuse of reader locktable slot",
 	"MDB_BAD_TXN: Transaction must abort, has a child, or is invalid",
 	"MDB_BAD_VALSIZE: Unsupported size of key/DB name/data, or wrong DUPFIXED size",
 	"MDB_BAD_DBI: The specified DBI handle was closed/changed unexpectedly",
 };
 
 char *
 mdb_strerror(int err)
 {
 #ifdef _WIN32
 	/** HACK: pad 4KB on stack over the buf. Return system msgs in buf.
 	 *	This works as long as no function between the call to mdb_strerror
 	 *	and the actual use of the message uses more than 4K of stack.
 	 */
 #define MSGSIZE	1024
 #define PADSIZE	4096
 	char buf[MSGSIZE+PADSIZE], *ptr = buf;
 #endif
 	int i;
 	if (!err)
 		return ("Successful return: 0");
 
 	if (err >= MDB_KEYEXIST && err <= MDB_LAST_ERRCODE) {
 		i = err - MDB_KEYEXIST;
 		return mdb_errstr[i];
 	}
 
 #ifdef _WIN32
 	/* These are the C-runtime error codes we use. The comment indicates
 	 * their numeric value, and the Win32 error they would correspond to
 	 * if the error actually came from a Win32 API. A major mess, we should
 	 * have used LMDB-specific error codes for everything.
 	 */
 	switch(err) {
 	case ENOENT:	/* 2, FILE_NOT_FOUND */
 	case EIO:		/* 5, ACCESS_DENIED */
 	case ENOMEM:	/* 12, INVALID_ACCESS */
 	case EACCES:	/* 13, INVALID_DATA */
 	case EBUSY:		/* 16, CURRENT_DIRECTORY */
 	case EINVAL:	/* 22, BAD_COMMAND */
 	case ENOSPC:	/* 28, OUT_OF_PAPER */
 		return strerror(err);
 	default:
 		;
 	}
 	buf[0] = 0;
 	FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM |
 		FORMAT_MESSAGE_IGNORE_INSERTS,
 		NULL, err, 0, ptr, MSGSIZE, (va_list *)buf+MSGSIZE);
 	return ptr;
 #else
 	if (err < 0)
 		return "Invalid error code";
 	return strerror(err);
 #endif
 }
 
 /** assert(3) variant in cursor context */
 #define mdb_cassert(mc, expr)	mdb_assert0((mc)->mc_txn->mt_env, expr, #expr)
 /** assert(3) variant in transaction context */
 #define mdb_tassert(txn, expr)	mdb_assert0((txn)->mt_env, expr, #expr)
 /** assert(3) variant in environment context */
 #define mdb_eassert(env, expr)	mdb_assert0(env, expr, #expr)
 
 #ifndef NDEBUG
 # define mdb_assert0(env, expr, expr_txt) ((expr) ? (void)0 : \
 		mdb_assert_fail(env, expr_txt, mdb_func_, __FILE__, __LINE__))
 
 static void ESECT
 mdb_assert_fail(MDB_env *env, const char *expr_txt,
 	const char *func, const char *file, int line)
 {
 	char buf[400];
 	sprintf(buf, "%.100s:%d: Assertion '%.200s' failed in %.40s()",
 		file, line, expr_txt, func);
 	if (env->me_assert_func)
 		env->me_assert_func(env, buf);
 	fprintf(stderr, "%s\n", buf);
 	abort();
 }
 #else
 # define mdb_assert0(env, expr, expr_txt) ((void) 0)
 #endif /* NDEBUG */
 
 #if MDB_DEBUG
 /** Return the page number of \b mp which may be sub-page, for debug output */
 static pgno_t
 mdb_dbg_pgno(MDB_page *mp)
 {
 	pgno_t ret;
 	COPY_PGNO(ret, MP_PGNO(mp));
 	return ret;
 }
 
 /** Display a key in hexadecimal and return the address of the result.
  * @param[in] key the key to display
  * @param[in] buf the buffer to write into. Should always be #DKBUF.
  * @return The key in hexadecimal form.
  */
 char *
 mdb_dkey(MDB_val *key, char *buf)
 {
 	char *ptr = buf;
 	unsigned char *c = key->mv_data;
 	unsigned int i;
 
 	if (!key)
 		return "";
 
 	if (key->mv_size > DKBUF_MAXKEYSIZE)
 		return "MDB_MAXKEYSIZE";
 	/* may want to make this a dynamic check: if the key is mostly
 	 * printable characters, print it as-is instead of converting to hex.
 	 */
 #if 1
 	buf[0] = '\0';
 	for (i=0; i<key->mv_size; i++)
 		ptr += sprintf(ptr, "%02x", *c++);
 #else
 	sprintf(buf, "%.*s", key->mv_size, key->mv_data);
 #endif
 	return buf;
 }
 
 static const char *
 mdb_leafnode_type(MDB_node *n)
 {
 	static char *const tp[2][2] = {{"", ": DB"}, {": sub-page", ": sub-DB"}};
 	return F_ISSET(n->mn_flags, F_BIGDATA) ? ": overflow page" :
 		tp[F_ISSET(n->mn_flags, F_DUPDATA)][F_ISSET(n->mn_flags, F_SUBDATA)];
 }
 
 /** Display all the keys in the page. */
 void
 mdb_page_list(MDB_page *mp)
 {
 	pgno_t pgno = mdb_dbg_pgno(mp);
 	const char *type, *state = (MP_FLAGS(mp) & P_DIRTY) ? ", dirty" : "";
 	MDB_node *node;
 	unsigned int i, nkeys, nsize, total = 0;
 	MDB_val key;
 	DKBUF;
 
 	switch (MP_FLAGS(mp) & (P_BRANCH|P_LEAF|P_LEAF2|P_META|P_OVERFLOW|P_SUBP)) {
 	case P_BRANCH:              type = "Branch page";		break;
 	case P_LEAF:                type = "Leaf page";			break;
 	case P_LEAF|P_SUBP:         type = "Sub-page";			break;
 	case P_LEAF|P_LEAF2:        type = "LEAF2 page";		break;
 	case P_LEAF|P_LEAF2|P_SUBP: type = "LEAF2 sub-page";	break;
 	case P_OVERFLOW:
 		fprintf(stderr, "Overflow page %"Z"u pages %u%s\n",
 			pgno, mp->mp_pages, state);
 		return;
 	case P_META:
 		fprintf(stderr, "Meta-page %"Z"u txnid %"Z"u\n",
 			pgno, ((MDB_meta *)METADATA(mp))->mm_txnid);
 		return;
 	default:
 		fprintf(stderr, "Bad page %"Z"u flags 0x%X\n", pgno, MP_FLAGS(mp));
 		return;
 	}
 
 	nkeys = NUMKEYS(mp);
 	fprintf(stderr, "%s %"Z"u numkeys %d%s\n", type, pgno, nkeys, state);
 
 	for (i=0; i<nkeys; i++) {
 		if (IS_LEAF2(mp)) {	/* LEAF2 pages have no mp_ptrs[] or node headers */
 			key.mv_size = nsize = mp->mp_pad;
 			key.mv_data = LEAF2KEY(mp, i, nsize);
 			total += nsize;
 			fprintf(stderr, "key %d: nsize %d, %s\n", i, nsize, DKEY(&key));
 			continue;
 		}
 		node = NODEPTR(mp, i);
 		key.mv_size = node->mn_ksize;
 		key.mv_data = node->mn_data;
 		nsize = NODESIZE + key.mv_size;
 		if (IS_BRANCH(mp)) {
 			fprintf(stderr, "key %d: page %"Z"u, %s\n", i, NODEPGNO(node),
 				DKEY(&key));
 			total += nsize;
 		} else {
 			if (F_ISSET(node->mn_flags, F_BIGDATA))
 				nsize += sizeof(pgno_t);
 			else
 				nsize += NODEDSZ(node);
 			total += nsize;
 			nsize += sizeof(indx_t);
 			fprintf(stderr, "key %d: nsize %d, %s%s\n",
 				i, nsize, DKEY(&key), mdb_leafnode_type(node));
 		}
 		total = EVEN(total);
 	}
 	fprintf(stderr, "Total: header %d + contents %d + unused %d\n",
 		IS_LEAF2(mp) ? PAGEHDRSZ : PAGEBASE + MP_LOWER(mp), total, SIZELEFT(mp));
 }
 
 void
 mdb_cursor_chk(MDB_cursor *mc)
 {
 	unsigned int i;
 	MDB_node *node;
 	MDB_page *mp;
 
 	if (!mc->mc_snum || !(mc->mc_flags & C_INITIALIZED)) return;
 	for (i=0; i<mc->mc_top; i++) {
 		mp = mc->mc_pg[i];
 		node = NODEPTR(mp, mc->mc_ki[i]);
 		if (NODEPGNO(node) != mc->mc_pg[i+1]->mp_pgno)
 			printf("oops!\n");
 	}
 	if (mc->mc_ki[i] >= NUMKEYS(mc->mc_pg[i]))
 		printf("ack!\n");
 	if (XCURSOR_INITED(mc)) {
 		node = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 		if (((node->mn_flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA) &&
 			mc->mc_xcursor->mx_cursor.mc_pg[0] != NODEDATA(node)) {
 			printf("blah!\n");
 		}
 	}
 }
 #endif
 
 #if (MDB_DEBUG) > 2
 /** Count all the pages in each DB and in the freelist
  *  and make sure it matches the actual number of pages
  *  being used.
  *  All named DBs must be open for a correct count.
  */
 static void mdb_audit(MDB_txn *txn)
 {
 	MDB_cursor mc;
 	MDB_val key, data;
 	MDB_ID freecount, count;
 	MDB_dbi i;
 	int rc;
 
 	freecount = 0;
 	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
 	while ((rc = mdb_cursor_get(&mc, &key, &data, MDB_NEXT)) == 0)
 		freecount += *(MDB_ID *)data.mv_data;
 	mdb_tassert(txn, rc == MDB_NOTFOUND);
 
 	count = 0;
 	for (i = 0; i<txn->mt_numdbs; i++) {
 		MDB_xcursor mx;
 		if (!(txn->mt_dbflags[i] & DB_VALID))
 			continue;
 		mdb_cursor_init(&mc, txn, i, &mx);
 		if (txn->mt_dbs[i].md_root == P_INVALID)
 			continue;
 		count += txn->mt_dbs[i].md_branch_pages +
 			txn->mt_dbs[i].md_leaf_pages +
 			txn->mt_dbs[i].md_overflow_pages;
 		if (txn->mt_dbs[i].md_flags & MDB_DUPSORT) {
 			rc = mdb_page_search(&mc, NULL, MDB_PS_FIRST);
 			for (; rc == MDB_SUCCESS; rc = mdb_cursor_sibling(&mc, 1)) {
 				unsigned j;
 				MDB_page *mp;
 				mp = mc.mc_pg[mc.mc_top];
 				for (j=0; j<NUMKEYS(mp); j++) {
 					MDB_node *leaf = NODEPTR(mp, j);
 					if (leaf->mn_flags & F_SUBDATA) {
 						MDB_db db;
 						memcpy(&db, NODEDATA(leaf), sizeof(db));
 						count += db.md_branch_pages + db.md_leaf_pages +
 							db.md_overflow_pages;
 					}
 				}
 			}
 			mdb_tassert(txn, rc == MDB_NOTFOUND);
 		}
 	}
 	if (freecount + count + NUM_METAS != txn->mt_next_pgno) {
 		fprintf(stderr, "audit: %"Z"u freecount: %"Z"u count: %"Z"u total: %"Z"u next_pgno: %"Z"u\n",
 			txn->mt_txnid, freecount, count+NUM_METAS,
 			freecount+count+NUM_METAS, txn->mt_next_pgno);
 	}
 }
 #endif
 
 int
 mdb_cmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
 {
 	return txn->mt_dbxs[dbi].md_cmp(a, b);
 }
 
 int
 mdb_dcmp(MDB_txn *txn, MDB_dbi dbi, const MDB_val *a, const MDB_val *b)
 {
 	MDB_cmp_func *dcmp = txn->mt_dbxs[dbi].md_dcmp;
 #if UINT_MAX < SIZE_MAX
 	if (dcmp == mdb_cmp_int && a->mv_size == sizeof(size_t))
 		dcmp = mdb_cmp_clong;
 #endif
 	return dcmp(a, b);
 }
 
 /** Allocate memory for a page.
  * Re-use old malloc'd pages first for singletons, otherwise just malloc.
  * Set #MDB_TXN_ERROR on failure.
  */
 static MDB_page *
 mdb_page_malloc(MDB_txn *txn, unsigned num)
 {
 	MDB_env *env = txn->mt_env;
 	MDB_page *ret = env->me_dpages;
 	size_t psize = env->me_psize, sz = psize, off;
 	/* For ! #MDB_NOMEMINIT, psize counts how much to init.
 	 * For a single page alloc, we init everything after the page header.
 	 * For multi-page, we init the final page; if the caller needed that
 	 * many pages they will be filling in at least up to the last page.
 	 */
 	if (num == 1) {
 		if (ret) {
 			VGMEMP_ALLOC(env, ret, sz);
 			VGMEMP_DEFINED(ret, sizeof(ret->mp_next));
 			env->me_dpages = ret->mp_next;
 			return ret;
 		}
 		psize -= off = PAGEHDRSZ;
 	} else {
 		sz *= num;
 		off = sz - psize;
 	}
 	if ((ret = malloc(sz)) != NULL) {
 		VGMEMP_ALLOC(env, ret, sz);
 		if (!(env->me_flags & MDB_NOMEMINIT)) {
 			memset((char *)ret + off, 0, psize);
 			ret->mp_pad = 0;
 		}
 	} else {
 		txn->mt_flags |= MDB_TXN_ERROR;
 	}
 	return ret;
 }
 /** Free a single page.
  * Saves single pages to a list, for future reuse.
  * (This is not used for multi-page overflow pages.)
  */
 static void
 mdb_page_free(MDB_env *env, MDB_page *mp)
 {
 	mp->mp_next = env->me_dpages;
 	VGMEMP_FREE(env, mp);
 	env->me_dpages = mp;
 }
 
 /** Free a dirty page */
 static void
 mdb_dpage_free(MDB_env *env, MDB_page *dp)
 {
 	if (!IS_OVERFLOW(dp) || dp->mp_pages == 1) {
 		mdb_page_free(env, dp);
 	} else {
 		/* large pages just get freed directly */
 		VGMEMP_FREE(env, dp);
 		free(dp);
 	}
 }
 
 /**	Return all dirty pages to dpage list */
 static void
 mdb_dlist_free(MDB_txn *txn)
 {
 	MDB_env *env = txn->mt_env;
 	MDB_ID2L dl = txn->mt_u.dirty_list;
 	unsigned i, n = dl[0].mid;
 
 	for (i = 1; i <= n; i++) {
 		mdb_dpage_free(env, dl[i].mptr);
 	}
 	dl[0].mid = 0;
 }
 
 /** Loosen or free a single page.
  * Saves single pages to a list for future reuse
  * in this same txn. It has been pulled from the freeDB
  * and already resides on the dirty list, but has been
  * deleted. Use these pages first before pulling again
  * from the freeDB.
  *
  * If the page wasn't dirtied in this txn, just add it
  * to this txn's free list.
  */
 static int
 mdb_page_loose(MDB_cursor *mc, MDB_page *mp)
 {
 	int loose = 0;
 	pgno_t pgno = mp->mp_pgno;
 	MDB_txn *txn = mc->mc_txn;
 
 	if ((mp->mp_flags & P_DIRTY) && mc->mc_dbi != FREE_DBI) {
 		if (txn->mt_parent) {
 			MDB_ID2 *dl = txn->mt_u.dirty_list;
 			/* If txn has a parent, make sure the page is in our
 			 * dirty list.
 			 */
 			if (dl[0].mid) {
 				unsigned x = mdb_mid2l_search(dl, pgno);
 				if (x <= dl[0].mid && dl[x].mid == pgno) {
 					if (mp != dl[x].mptr) { /* bad cursor? */
 						mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
 						txn->mt_flags |= MDB_TXN_ERROR;
 						return MDB_CORRUPTED;
 					}
 					/* ok, it's ours */
 					loose = 1;
 				}
 			}
 		} else {
 			/* no parent txn, so it's just ours */
 			loose = 1;
 		}
 	}
 	if (loose) {
 		DPRINTF(("loosen db %d page %"Z"u", DDBI(mc),
 			mp->mp_pgno));
 		NEXT_LOOSE_PAGE(mp) = txn->mt_loose_pgs;
 		txn->mt_loose_pgs = mp;
 		txn->mt_loose_count++;
 		mp->mp_flags |= P_LOOSE;
 	} else {
 		int rc = mdb_midl_append(&txn->mt_free_pgs, pgno);
 		if (rc)
 			return rc;
 	}
 
 	return MDB_SUCCESS;
 }
 
 /** Set or clear P_KEEP in dirty, non-overflow, non-sub pages watched by txn.
  * @param[in] mc A cursor handle for the current operation.
  * @param[in] pflags Flags of the pages to update:
  * P_DIRTY to set P_KEEP, P_DIRTY|P_KEEP to clear it.
  * @param[in] all No shortcuts. Needed except after a full #mdb_page_flush().
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_pages_xkeep(MDB_cursor *mc, unsigned pflags, int all)
 {
 	enum { Mask = P_SUBP|P_DIRTY|P_LOOSE|P_KEEP };
 	MDB_txn *txn = mc->mc_txn;
 	MDB_cursor *m3, *m0 = mc;
 	MDB_xcursor *mx;
 	MDB_page *dp, *mp;
 	MDB_node *leaf;
 	unsigned i, j;
 	int rc = MDB_SUCCESS, level;
 
 	/* Mark pages seen by cursors */
 	if (mc->mc_flags & C_UNTRACK)
 		mc = NULL;				/* will find mc in mt_cursors */
 	for (i = txn->mt_numdbs;; mc = txn->mt_cursors[--i]) {
 		for (; mc; mc=mc->mc_next) {
 			if (!(mc->mc_flags & C_INITIALIZED))
 				continue;
 			for (m3 = mc;; m3 = &mx->mx_cursor) {
 				mp = NULL;
 				for (j=0; j<m3->mc_snum; j++) {
 					mp = m3->mc_pg[j];
 					if ((mp->mp_flags & Mask) == pflags)
 						mp->mp_flags ^= P_KEEP;
 				}
 				mx = m3->mc_xcursor;
 				/* Proceed to mx if it is at a sub-database */
 				if (! (mx && (mx->mx_cursor.mc_flags & C_INITIALIZED)))
 					break;
 				if (! (mp && (mp->mp_flags & P_LEAF)))
 					break;
 				leaf = NODEPTR(mp, m3->mc_ki[j-1]);
 				if (!(leaf->mn_flags & F_SUBDATA))
 					break;
 			}
 		}
 		if (i == 0)
 			break;
 	}
 
 	if (all) {
 		/* Mark dirty root pages */
 		for (i=0; i<txn->mt_numdbs; i++) {
 			if (txn->mt_dbflags[i] & DB_DIRTY) {
 				pgno_t pgno = txn->mt_dbs[i].md_root;
 				if (pgno == P_INVALID)
 					continue;
 				if ((rc = mdb_page_get(m0, pgno, &dp, &level)) != MDB_SUCCESS)
 					break;
 				if ((dp->mp_flags & Mask) == pflags && level <= 1)
 					dp->mp_flags ^= P_KEEP;
 			}
 		}
 	}
 
 	return rc;
 }
 
 static int mdb_page_flush(MDB_txn *txn, int keep);
 
 /**	Spill pages from the dirty list back to disk.
  * This is intended to prevent running into #MDB_TXN_FULL situations,
  * but note that they may still occur in a few cases:
  *	1) our estimate of the txn size could be too small. Currently this
  *	 seems unlikely, except with a large number of #MDB_MULTIPLE items.
  *	2) child txns may run out of space if their parents dirtied a
  *	 lot of pages and never spilled them. TODO: we probably should do
  *	 a preemptive spill during #mdb_txn_begin() of a child txn, if
  *	 the parent's dirty_room is below a given threshold.
  *
  * Otherwise, if not using nested txns, it is expected that apps will
  * not run into #MDB_TXN_FULL any more. The pages are flushed to disk
  * the same way as for a txn commit, e.g. their P_DIRTY flag is cleared.
  * If the txn never references them again, they can be left alone.
  * If the txn only reads them, they can be used without any fuss.
  * If the txn writes them again, they can be dirtied immediately without
  * going thru all of the work of #mdb_page_touch(). Such references are
  * handled by #mdb_page_unspill().
  *
  * Also note, we never spill DB root pages, nor pages of active cursors,
  * because we'll need these back again soon anyway. And in nested txns,
  * we can't spill a page in a child txn if it was already spilled in a
  * parent txn. That would alter the parent txns' data even though
  * the child hasn't committed yet, and we'd have no way to undo it if
  * the child aborted.
  *
  * @param[in] m0 cursor A cursor handle identifying the transaction and
  *	database for which we are checking space.
  * @param[in] key For a put operation, the key being stored.
  * @param[in] data For a put operation, the data being stored.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_spill(MDB_cursor *m0, MDB_val *key, MDB_val *data)
 {
 	MDB_txn *txn = m0->mc_txn;
 	MDB_page *dp;
 	MDB_ID2L dl = txn->mt_u.dirty_list;
 	unsigned int i, j, need;
 	int rc;
 
 	if (m0->mc_flags & C_SUB)
 		return MDB_SUCCESS;
 
 	/* Estimate how much space this op will take */
 	i = m0->mc_db->md_depth;
 	/* Named DBs also dirty the main DB */
 	if (m0->mc_dbi >= CORE_DBS)
 		i += txn->mt_dbs[MAIN_DBI].md_depth;
 	/* For puts, roughly factor in the key+data size */
 	if (key)
 		i += (LEAFSIZE(key, data) + txn->mt_env->me_psize) / txn->mt_env->me_psize;
 	i += i;	/* double it for good measure */
 	need = i;
 
 	if (txn->mt_dirty_room > i)
 		return MDB_SUCCESS;
 
 	if (!txn->mt_spill_pgs) {
 		txn->mt_spill_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX);
 		if (!txn->mt_spill_pgs)
 			return ENOMEM;
 	} else {
 		/* purge deleted slots */
 		MDB_IDL sl = txn->mt_spill_pgs;
 		unsigned int num = sl[0];
 		j=0;
 		for (i=1; i<=num; i++) {
 			if (!(sl[i] & 1))
 				sl[++j] = sl[i];
 		}
 		sl[0] = j;
 	}
 
 	/* Preserve pages which may soon be dirtied again */
 	if ((rc = mdb_pages_xkeep(m0, P_DIRTY, 1)) != MDB_SUCCESS)
 		goto done;
 
 	/* Less aggressive spill - we originally spilled the entire dirty list,
 	 * with a few exceptions for cursor pages and DB root pages. But this
 	 * turns out to be a lot of wasted effort because in a large txn many
 	 * of those pages will need to be used again. So now we spill only 1/8th
 	 * of the dirty pages. Testing revealed this to be a good tradeoff,
 	 * better than 1/2, 1/4, or 1/10.
 	 */
 	if (need < MDB_IDL_UM_MAX / 8)
 		need = MDB_IDL_UM_MAX / 8;
 
 	/* Save the page IDs of all the pages we're flushing */
 	/* flush from the tail forward, this saves a lot of shifting later on. */
 	for (i=dl[0].mid; i && need; i--) {
 		MDB_ID pn = dl[i].mid << 1;
 		dp = dl[i].mptr;
 		if (dp->mp_flags & (P_LOOSE|P_KEEP))
 			continue;
 		/* Can't spill twice, make sure it's not already in a parent's
 		 * spill list.
 		 */
 		if (txn->mt_parent) {
 			MDB_txn *tx2;
 			for (tx2 = txn->mt_parent; tx2; tx2 = tx2->mt_parent) {
 				if (tx2->mt_spill_pgs) {
 					j = mdb_midl_search(tx2->mt_spill_pgs, pn);
 					if (j <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[j] == pn) {
 						dp->mp_flags |= P_KEEP;
 						break;
 					}
 				}
 			}
 			if (tx2)
 				continue;
 		}
 		if ((rc = mdb_midl_append(&txn->mt_spill_pgs, pn)))
 			goto done;
 		need--;
 	}
 	mdb_midl_sort(txn->mt_spill_pgs);
 
 	/* Flush the spilled part of dirty list */
 	if ((rc = mdb_page_flush(txn, i)) != MDB_SUCCESS)
 		goto done;
 
 	/* Reset any dirty pages we kept that page_flush didn't see */
 	rc = mdb_pages_xkeep(m0, P_DIRTY|P_KEEP, i);
 
 done:
 	txn->mt_flags |= rc ? MDB_TXN_ERROR : MDB_TXN_SPILLS;
 	return rc;
 }
 
 /** Find oldest txnid still referenced. Expects txn->mt_txnid > 0. */
 static txnid_t
 mdb_find_oldest(MDB_txn *txn)
 {
 	int i;
 	txnid_t mr, oldest = txn->mt_txnid - 1;
 	if (txn->mt_env->me_txns) {
 		MDB_reader *r = txn->mt_env->me_txns->mti_readers;
 		for (i = txn->mt_env->me_txns->mti_numreaders; --i >= 0; ) {
 			if (r[i].mr_pid) {
 				mr = r[i].mr_txnid;
 				if (oldest > mr)
 					oldest = mr;
 			}
 		}
 	}
 	return oldest;
 }
 
 /** Add a page to the txn's dirty list */
 static void
 mdb_page_dirty(MDB_txn *txn, MDB_page *mp)
 {
 	MDB_ID2 mid;
 	int rc, (*insert)(MDB_ID2L, MDB_ID2 *);
 
 	if (txn->mt_flags & MDB_TXN_WRITEMAP) {
 		insert = mdb_mid2l_append;
 	} else {
 		insert = mdb_mid2l_insert;
 	}
 	mid.mid = mp->mp_pgno;
 	mid.mptr = mp;
 	rc = insert(txn->mt_u.dirty_list, &mid);
 	mdb_tassert(txn, rc == 0);
 	txn->mt_dirty_room--;
 }
 
 /** Allocate page numbers and memory for writing.  Maintain me_pglast,
  * me_pghead and mt_next_pgno.  Set #MDB_TXN_ERROR on failure.
  *
  * If there are free pages available from older transactions, they
  * are re-used first. Otherwise allocate a new page at mt_next_pgno.
  * Do not modify the freedB, just merge freeDB records into me_pghead[]
  * and move me_pglast to say which records were consumed.  Only this
  * function can create me_pghead and move me_pglast/mt_next_pgno.
  * @param[in] mc cursor A cursor handle identifying the transaction and
  *	database for which we are allocating.
  * @param[in] num the number of pages to allocate.
  * @param[out] mp Address of the allocated page(s). Requests for multiple pages
  *  will always be satisfied by a single contiguous chunk of memory.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_alloc(MDB_cursor *mc, int num, MDB_page **mp)
 {
 #ifdef MDB_PARANOID	/* Seems like we can ignore this now */
 	/* Get at most <Max_retries> more freeDB records once me_pghead
 	 * has enough pages.  If not enough, use new pages from the map.
 	 * If <Paranoid> and mc is updating the freeDB, only get new
 	 * records if me_pghead is empty. Then the freelist cannot play
 	 * catch-up with itself by growing while trying to save it.
 	 */
 	enum { Paranoid = 1, Max_retries = 500 };
 #else
 	enum { Paranoid = 0, Max_retries = INT_MAX /*infinite*/ };
 #endif
 	int rc, retry = num * 60;
 	MDB_txn *txn = mc->mc_txn;
 	MDB_env *env = txn->mt_env;
 	pgno_t pgno, *mop = env->me_pghead;
 	unsigned i, j, mop_len = mop ? mop[0] : 0, n2 = num-1;
 	MDB_page *np;
 	txnid_t oldest = 0, last;
 	MDB_cursor_op op;
 	MDB_cursor m2;
 	int found_old = 0;
 
 	/* If there are any loose pages, just use them */
 	if (num == 1 && txn->mt_loose_pgs) {
 		np = txn->mt_loose_pgs;
 		txn->mt_loose_pgs = NEXT_LOOSE_PAGE(np);
 		txn->mt_loose_count--;
 		DPRINTF(("db %d use loose page %"Z"u", DDBI(mc),
 				np->mp_pgno));
 		*mp = np;
 		return MDB_SUCCESS;
 	}
 
 	*mp = NULL;
 
 	/* If our dirty list is already full, we can't do anything */
 	if (txn->mt_dirty_room == 0) {
 		rc = MDB_TXN_FULL;
 		goto fail;
 	}
 
 	for (op = MDB_FIRST;; op = MDB_NEXT) {
 		MDB_val key, data;
 		MDB_node *leaf;
 		pgno_t *idl;
 
 		/* Seek a big enough contiguous page range. Prefer
 		 * pages at the tail, just truncating the list.
 		 */
 		if (mop_len > n2) {
 			i = mop_len;
 			do {
 				pgno = mop[i];
 				if (mop[i-n2] == pgno+n2)
 					goto search_done;
 			} while (--i > n2);
 			if (--retry < 0)
 				break;
 		}
 
 		if (op == MDB_FIRST) {	/* 1st iteration */
 			/* Prepare to fetch more and coalesce */
 			last = env->me_pglast;
 			oldest = env->me_pgoldest;
 			mdb_cursor_init(&m2, txn, FREE_DBI, NULL);
 			if (last) {
 				op = MDB_SET_RANGE;
 				key.mv_data = &last; /* will look up last+1 */
 				key.mv_size = sizeof(last);
 			}
 			if (Paranoid && mc->mc_dbi == FREE_DBI)
 				retry = -1;
 		}
 		if (Paranoid && retry < 0 && mop_len)
 			break;
 
 		last++;
 		/* Do not fetch more if the record will be too recent */
 		if (oldest <= last) {
 			if (!found_old) {
 				oldest = mdb_find_oldest(txn);
 				env->me_pgoldest = oldest;
 				found_old = 1;
 			}
 			if (oldest <= last)
 				break;
 		}
 		rc = mdb_cursor_get(&m2, &key, NULL, op);
 		if (rc) {
 			if (rc == MDB_NOTFOUND)
 				break;
 			goto fail;
 		}
 		last = *(txnid_t*)key.mv_data;
 		if (oldest <= last) {
 			if (!found_old) {
 				oldest = mdb_find_oldest(txn);
 				env->me_pgoldest = oldest;
 				found_old = 1;
 			}
 			if (oldest <= last)
 				break;
 		}
 		np = m2.mc_pg[m2.mc_top];
 		leaf = NODEPTR(np, m2.mc_ki[m2.mc_top]);
 		if ((rc = mdb_node_read(&m2, leaf, &data)) != MDB_SUCCESS)
 			goto fail;
 
 		idl = (MDB_ID *) data.mv_data;
 		i = idl[0];
 		if (!mop) {
 			if (!(env->me_pghead = mop = mdb_midl_alloc(i))) {
 				rc = ENOMEM;
 				goto fail;
 			}
 		} else {
 			if ((rc = mdb_midl_need(&env->me_pghead, i)) != 0)
 				goto fail;
 			mop = env->me_pghead;
 		}
 		env->me_pglast = last;
 #if (MDB_DEBUG) > 1
 		DPRINTF(("IDL read txn %"Z"u root %"Z"u num %u",
 			last, txn->mt_dbs[FREE_DBI].md_root, i));
 		for (j = i; j; j--)
 			DPRINTF(("IDL %"Z"u", idl[j]));
 #endif
 		/* Merge in descending sorted order */
 		mdb_midl_xmerge(mop, idl);
 		mop_len = mop[0];
 	}
 
 	/* Use new pages from the map when nothing suitable in the freeDB */
 	i = 0;
 	pgno = txn->mt_next_pgno;
 	if (pgno + num >= env->me_maxpg) {
 			DPUTS("DB size maxed out");
 			rc = MDB_MAP_FULL;
 			goto fail;
 	}
 
 search_done:
 	if (env->me_flags & MDB_WRITEMAP) {
 		np = (MDB_page *)(env->me_map + env->me_psize * pgno);
 	} else {
 		if (!(np = mdb_page_malloc(txn, num))) {
 			rc = ENOMEM;
 			goto fail;
 		}
 	}
 	if (i) {
 		mop[0] = mop_len -= num;
 		/* Move any stragglers down */
 		for (j = i-num; j < mop_len; )
 			mop[++j] = mop[++i];
 	} else {
 		txn->mt_next_pgno = pgno + num;
 	}
 	np->mp_pgno = pgno;
 	mdb_page_dirty(txn, np);
 	*mp = np;
 
 	return MDB_SUCCESS;
 
 fail:
 	txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 /** Copy the used portions of a non-overflow page.
  * @param[in] dst page to copy into
  * @param[in] src page to copy from
  * @param[in] psize size of a page
  */
 static void
 mdb_page_copy(MDB_page *dst, MDB_page *src, unsigned int psize)
 {
 	enum { Align = sizeof(pgno_t) };
 	indx_t upper = src->mp_upper, lower = src->mp_lower, unused = upper-lower;
 
 	/* If page isn't full, just copy the used portion. Adjust
 	 * alignment so memcpy may copy words instead of bytes.
 	 */
 	if ((unused &= -Align) && !IS_LEAF2(src)) {
 		upper = (upper + PAGEBASE) & -Align;
 		memcpy(dst, src, (lower + PAGEBASE + (Align-1)) & -Align);
 		memcpy((pgno_t *)((char *)dst+upper), (pgno_t *)((char *)src+upper),
 			psize - upper);
 	} else {
 		memcpy(dst, src, psize - unused);
 	}
 }
 
 /** Pull a page off the txn's spill list, if present.
  * If a page being referenced was spilled to disk in this txn, bring
  * it back and make it dirty/writable again.
  * @param[in] txn the transaction handle.
  * @param[in] mp the page being referenced. It must not be dirty.
  * @param[out] ret the writable page, if any. ret is unchanged if
  * mp wasn't spilled.
  */
 static int
 mdb_page_unspill(MDB_txn *txn, MDB_page *mp, MDB_page **ret)
 {
 	MDB_env *env = txn->mt_env;
 	const MDB_txn *tx2;
 	unsigned x;
 	pgno_t pgno = mp->mp_pgno, pn = pgno << 1;
 
 	for (tx2 = txn; tx2; tx2=tx2->mt_parent) {
 		if (!tx2->mt_spill_pgs)
 			continue;
 		x = mdb_midl_search(tx2->mt_spill_pgs, pn);
 		if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
 			MDB_page *np;
 			int num;
 			if (txn->mt_dirty_room == 0)
 				return MDB_TXN_FULL;
 			if (IS_OVERFLOW(mp))
 				num = mp->mp_pages;
 			else
 				num = 1;
 			if (env->me_flags & MDB_WRITEMAP) {
 				np = mp;
 			} else {
 				np = mdb_page_malloc(txn, num);
 				if (!np)
 					return ENOMEM;
 				if (num > 1)
 					memcpy(np, mp, num * env->me_psize);
 				else
 					mdb_page_copy(np, mp, env->me_psize);
 			}
 			if (tx2 == txn) {
 				/* If in current txn, this page is no longer spilled.
 				 * If it happens to be the last page, truncate the spill list.
 				 * Otherwise mark it as deleted by setting the LSB.
 				 */
 				if (x == txn->mt_spill_pgs[0])
 					txn->mt_spill_pgs[0]--;
 				else
 					txn->mt_spill_pgs[x] |= 1;
 			}	/* otherwise, if belonging to a parent txn, the
 				 * page remains spilled until child commits
 				 */
 
 			mdb_page_dirty(txn, np);
 			np->mp_flags |= P_DIRTY;
 			*ret = np;
 			break;
 		}
 	}
 	return MDB_SUCCESS;
 }
 
 /** Touch a page: make it dirty and re-insert into tree with updated pgno.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in] mc cursor pointing to the page to be touched
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_touch(MDB_cursor *mc)
 {
 	MDB_page *mp = mc->mc_pg[mc->mc_top], *np;
 	MDB_txn *txn = mc->mc_txn;
 	MDB_cursor *m2, *m3;
 	pgno_t	pgno;
 	int rc;
 
 	if (!F_ISSET(MP_FLAGS(mp), P_DIRTY)) {
 		if (txn->mt_flags & MDB_TXN_SPILLS) {
 			np = NULL;
 			rc = mdb_page_unspill(txn, mp, &np);
 			if (rc)
 				goto fail;
 			if (np)
 				goto done;
 		}
 		if ((rc = mdb_midl_need(&txn->mt_free_pgs, 1)) ||
 			(rc = mdb_page_alloc(mc, 1, &np)))
 			goto fail;
 		pgno = np->mp_pgno;
 		DPRINTF(("touched db %d page %"Z"u -> %"Z"u", DDBI(mc),
 			mp->mp_pgno, pgno));
 		mdb_cassert(mc, mp->mp_pgno != pgno);
 		mdb_midl_xappend(txn->mt_free_pgs, mp->mp_pgno);
 		/* Update the parent page, if any, to point to the new page */
 		if (mc->mc_top) {
 			MDB_page *parent = mc->mc_pg[mc->mc_top-1];
 			MDB_node *node = NODEPTR(parent, mc->mc_ki[mc->mc_top-1]);
 			SETPGNO(node, pgno);
 		} else {
 			mc->mc_db->md_root = pgno;
 		}
 	} else if (txn->mt_parent && !IS_SUBP(mp)) {
 		MDB_ID2 mid, *dl = txn->mt_u.dirty_list;
 		pgno = mp->mp_pgno;
 		/* If txn has a parent, make sure the page is in our
 		 * dirty list.
 		 */
 		if (dl[0].mid) {
 			unsigned x = mdb_mid2l_search(dl, pgno);
 			if (x <= dl[0].mid && dl[x].mid == pgno) {
 				if (mp != dl[x].mptr) { /* bad cursor? */
 					mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
 					txn->mt_flags |= MDB_TXN_ERROR;
 					return MDB_CORRUPTED;
 				}
 				return 0;
 			}
 		}
 		mdb_cassert(mc, dl[0].mid < MDB_IDL_UM_MAX);
 		/* No - copy it */
 		np = mdb_page_malloc(txn, 1);
 		if (!np)
 			return ENOMEM;
 		mid.mid = pgno;
 		mid.mptr = np;
 		rc = mdb_mid2l_insert(dl, &mid);
 		mdb_cassert(mc, rc == 0);
 	} else {
 		return 0;
 	}
 
 	mdb_page_copy(np, mp, txn->mt_env->me_psize);
 	np->mp_pgno = pgno;
 	np->mp_flags |= P_DIRTY;
 
 done:
 	/* Adjust cursors pointing to mp */
 	mc->mc_pg[mc->mc_top] = np;
 	m2 = txn->mt_cursors[mc->mc_dbi];
 	if (mc->mc_flags & C_SUB) {
 		for (; m2; m2=m2->mc_next) {
 			m3 = &m2->mc_xcursor->mx_cursor;
 			if (m3->mc_snum < mc->mc_snum) continue;
 			if (m3->mc_pg[mc->mc_top] == mp)
 				m3->mc_pg[mc->mc_top] = np;
 		}
 	} else {
 		for (; m2; m2=m2->mc_next) {
 			if (m2->mc_snum < mc->mc_snum) continue;
 			if (m2 == mc) continue;
 			if (m2->mc_pg[mc->mc_top] == mp) {
 				m2->mc_pg[mc->mc_top] = np;
 				if (IS_LEAF(np))
 					XCURSOR_REFRESH(m2, mc->mc_top, np);
 			}
 		}
 	}
 	return 0;
 
 fail:
 	txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 int
 mdb_env_sync(MDB_env *env, int force)
 {
 	int rc = 0;
 	if (env->me_flags & MDB_RDONLY)
 		return EACCES;
 	if (force || !F_ISSET(env->me_flags, MDB_NOSYNC)) {
 		if (env->me_flags & MDB_WRITEMAP) {
 			int flags = ((env->me_flags & MDB_MAPASYNC) && !force)
 				? MS_ASYNC : MS_SYNC;
 			if (MDB_MSYNC(env->me_map, env->me_mapsize, flags))
 				rc = ErrCode();
 #ifdef _WIN32
 			else if (flags == MS_SYNC && MDB_FDATASYNC(env->me_fd))
 				rc = ErrCode();
 #endif
 		} else {
 #ifdef BROKEN_FDATASYNC
 			if (env->me_flags & MDB_FSYNCONLY) {
 				if (fsync(env->me_fd))
 					rc = ErrCode();
 			} else
 #endif
 			if (MDB_FDATASYNC(env->me_fd))
 				rc = ErrCode();
 		}
 	}
 	return rc;
 }
 
 /** Back up parent txn's cursors, then grab the originals for tracking */
 static int
 mdb_cursor_shadow(MDB_txn *src, MDB_txn *dst)
 {
 	MDB_cursor *mc, *bk;
 	MDB_xcursor *mx;
 	size_t size;
 	int i;
 
 	for (i = src->mt_numdbs; --i >= 0; ) {
 		if ((mc = src->mt_cursors[i]) != NULL) {
 			size = sizeof(MDB_cursor);
 			if (mc->mc_xcursor)
 				size += sizeof(MDB_xcursor);
 			for (; mc; mc = bk->mc_next) {
 				bk = malloc(size);
 				if (!bk)
 					return ENOMEM;
 				*bk = *mc;
 				mc->mc_backup = bk;
 				mc->mc_db = &dst->mt_dbs[i];
 				/* Kill pointers into src to reduce abuse: The
 				 * user may not use mc until dst ends. But we need a valid
 				 * txn pointer here for cursor fixups to keep working.
 				 */
 				mc->mc_txn    = dst;
 				mc->mc_dbflag = &dst->mt_dbflags[i];
 				if ((mx = mc->mc_xcursor) != NULL) {
 					*(MDB_xcursor *)(bk+1) = *mx;
 					mx->mx_cursor.mc_txn = dst;
 				}
 				mc->mc_next = dst->mt_cursors[i];
 				dst->mt_cursors[i] = mc;
 			}
 		}
 	}
 	return MDB_SUCCESS;
 }
 
 /** Close this write txn's cursors, give parent txn's cursors back to parent.
  * @param[in] txn the transaction handle.
  * @param[in] merge true to keep changes to parent cursors, false to revert.
  * @return 0 on success, non-zero on failure.
  */
 static void
 mdb_cursors_close(MDB_txn *txn, unsigned merge)
 {
 	MDB_cursor **cursors = txn->mt_cursors, *mc, *next, *bk;
 	MDB_xcursor *mx;
 	int i;
 
 	for (i = txn->mt_numdbs; --i >= 0; ) {
 		for (mc = cursors[i]; mc; mc = next) {
 			next = mc->mc_next;
 			if ((bk = mc->mc_backup) != NULL) {
 				if (merge) {
 					/* Commit changes to parent txn */
 					mc->mc_next = bk->mc_next;
 					mc->mc_backup = bk->mc_backup;
 					mc->mc_txn = bk->mc_txn;
 					mc->mc_db = bk->mc_db;
 					mc->mc_dbflag = bk->mc_dbflag;
 					if ((mx = mc->mc_xcursor) != NULL)
 						mx->mx_cursor.mc_txn = bk->mc_txn;
 				} else {
 					/* Abort nested txn */
 					*mc = *bk;
 					if ((mx = mc->mc_xcursor) != NULL)
 						*mx = *(MDB_xcursor *)(bk+1);
 				}
 				mc = bk;
 			}
 			/* Only malloced cursors are permanently tracked. */
 			free(mc);
 		}
 		cursors[i] = NULL;
 	}
 }
 
 #if !(MDB_PIDLOCK)		/* Currently the same as defined(_WIN32) */
 enum Pidlock_op {
 	Pidset, Pidcheck
 };
 #else
 enum Pidlock_op {
 	Pidset = F_SETLK, Pidcheck = F_GETLK
 };
 #endif
 
 /** Set or check a pid lock. Set returns 0 on success.
  * Check returns 0 if the process is certainly dead, nonzero if it may
  * be alive (the lock exists or an error happened so we do not know).
  *
  * On Windows Pidset is a no-op, we merely check for the existence
  * of the process with the given pid. On POSIX we use a single byte
  * lock on the lockfile, set at an offset equal to the pid.
  */
 static int
 mdb_reader_pid(MDB_env *env, enum Pidlock_op op, MDB_PID_T pid)
 {
 #if !(MDB_PIDLOCK)		/* Currently the same as defined(_WIN32) */
 	int ret = 0;
 	HANDLE h;
 	if (op == Pidcheck) {
 		h = OpenProcess(env->me_pidquery, FALSE, pid);
 		/* No documented "no such process" code, but other program use this: */
 		if (!h)
 			return ErrCode() != ERROR_INVALID_PARAMETER;
 		/* A process exists until all handles to it close. Has it exited? */
 		ret = WaitForSingleObject(h, 0) != 0;
 		CloseHandle(h);
 	}
 	return ret;
 #else
 	for (;;) {
 		int rc;
 		struct flock lock_info;
 		memset(&lock_info, 0, sizeof(lock_info));
 		lock_info.l_type = F_WRLCK;
 		lock_info.l_whence = SEEK_SET;
 		lock_info.l_start = pid;
 		lock_info.l_len = 1;
 		if ((rc = fcntl(env->me_lfd, op, &lock_info)) == 0) {
 			if (op == F_GETLK && lock_info.l_type != F_UNLCK)
 				rc = -1;
 		} else if ((rc = ErrCode()) == EINTR) {
 			continue;
 		}
 		return rc;
 	}
 #endif
 }
 
 /** Common code for #mdb_txn_begin() and #mdb_txn_renew().
  * @param[in] txn the transaction handle to initialize
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_txn_renew0(MDB_txn *txn)
 {
 	MDB_env *env = txn->mt_env;
 	MDB_txninfo *ti = env->me_txns;
 	MDB_meta *meta;
 	unsigned int i, nr, flags = txn->mt_flags;
 	uint16_t x;
 	int rc, new_notls = 0;
 
 	if ((flags &= MDB_TXN_RDONLY) != 0) {
 		if (!ti) {
 			meta = mdb_env_pick_meta(env);
 			txn->mt_txnid = meta->mm_txnid;
 			txn->mt_u.reader = NULL;
 		} else {
 			MDB_reader *r = (env->me_flags & MDB_NOTLS) ? txn->mt_u.reader :
 				pthread_getspecific(env->me_txkey);
 			if (r) {
 				if (r->mr_pid != env->me_pid || r->mr_txnid != (txnid_t)-1)
 					return MDB_BAD_RSLOT;
 			} else {
 				MDB_PID_T pid = env->me_pid;
 				MDB_THR_T tid = pthread_self();
 				mdb_mutexref_t rmutex = env->me_rmutex;
 
 				if (!env->me_live_reader) {
 					rc = mdb_reader_pid(env, Pidset, pid);
 					if (rc)
 						return rc;
 					env->me_live_reader = 1;
 				}
 
 				if (LOCK_MUTEX(rc, env, rmutex))
 					return rc;
 				nr = ti->mti_numreaders;
 				for (i=0; i<nr; i++)
 					if (ti->mti_readers[i].mr_pid == 0)
 						break;
 				if (i == env->me_maxreaders) {
 					UNLOCK_MUTEX(rmutex);
 					return MDB_READERS_FULL;
 				}
 				r = &ti->mti_readers[i];
 				/* Claim the reader slot, carefully since other code
 				 * uses the reader table un-mutexed: First reset the
 				 * slot, next publish it in mti_numreaders.  After
 				 * that, it is safe for mdb_env_close() to touch it.
 				 * When it will be closed, we can finally claim it.
 				 */
 				r->mr_pid = 0;
 				r->mr_txnid = (txnid_t)-1;
 				r->mr_tid = tid;
 				if (i == nr)
 					ti->mti_numreaders = ++nr;
 				env->me_close_readers = nr;
 				r->mr_pid = pid;
 				UNLOCK_MUTEX(rmutex);
 
 				new_notls = (env->me_flags & MDB_NOTLS);
 				if (!new_notls && (rc=pthread_setspecific(env->me_txkey, r))) {
 					r->mr_pid = 0;
 					return rc;
 				}
 			}
 			do /* LY: Retry on a race, ITS#7970. */
 				r->mr_txnid = ti->mti_txnid;
 			while(r->mr_txnid != ti->mti_txnid);
 			txn->mt_txnid = r->mr_txnid;
 			txn->mt_u.reader = r;
 			meta = env->me_metas[txn->mt_txnid & 1];
 		}
 
 	} else {
 		/* Not yet touching txn == env->me_txn0, it may be active */
 		if (ti) {
 			if (LOCK_MUTEX(rc, env, env->me_wmutex))
 				return rc;
 			txn->mt_txnid = ti->mti_txnid;
 			meta = env->me_metas[txn->mt_txnid & 1];
 		} else {
 			meta = mdb_env_pick_meta(env);
 			txn->mt_txnid = meta->mm_txnid;
 		}
 		txn->mt_txnid++;
 #if MDB_DEBUG
 		if (txn->mt_txnid == mdb_debug_start)
 			mdb_debug = 1;
 #endif
 		txn->mt_child = NULL;
 		txn->mt_loose_pgs = NULL;
 		txn->mt_loose_count = 0;
 		txn->mt_dirty_room = MDB_IDL_UM_MAX;
 		txn->mt_u.dirty_list = env->me_dirty_list;
 		txn->mt_u.dirty_list[0].mid = 0;
 		txn->mt_free_pgs = env->me_free_pgs;
 		txn->mt_free_pgs[0] = 0;
 		txn->mt_spill_pgs = NULL;
 		env->me_txn = txn;
 		memcpy(txn->mt_dbiseqs, env->me_dbiseqs, env->me_maxdbs * sizeof(unsigned int));
 	}
 
 	/* Copy the DB info and flags */
 	memcpy(txn->mt_dbs, meta->mm_dbs, CORE_DBS * sizeof(MDB_db));
 
 	/* Moved to here to avoid a data race in read TXNs */
 	txn->mt_next_pgno = meta->mm_last_pg+1;
 
 	txn->mt_flags = flags;
 
 	/* Setup db info */
 	txn->mt_numdbs = env->me_numdbs;
 	for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
 		x = env->me_dbflags[i];
 		txn->mt_dbs[i].md_flags = x & PERSISTENT_FLAGS;
 		txn->mt_dbflags[i] = (x & MDB_VALID) ? DB_VALID|DB_USRVALID|DB_STALE : 0;
 	}
 	txn->mt_dbflags[MAIN_DBI] = DB_VALID|DB_USRVALID;
 	txn->mt_dbflags[FREE_DBI] = DB_VALID;
 
 	if (env->me_flags & MDB_FATAL_ERROR) {
 		DPUTS("environment had fatal error, must shutdown!");
 		rc = MDB_PANIC;
 	} else if (env->me_maxpg < txn->mt_next_pgno) {
 		rc = MDB_MAP_RESIZED;
 	} else {
 		return MDB_SUCCESS;
 	}
 	mdb_txn_end(txn, new_notls /*0 or MDB_END_SLOT*/ | MDB_END_FAIL_BEGIN);
 	return rc;
 }
 
 int
 mdb_txn_renew(MDB_txn *txn)
 {
 	int rc;
 
 	if (!txn || !F_ISSET(txn->mt_flags, MDB_TXN_RDONLY|MDB_TXN_FINISHED))
 		return EINVAL;
 
 	rc = mdb_txn_renew0(txn);
 	if (rc == MDB_SUCCESS) {
 		DPRINTF(("renew txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
 			txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
 			(void *)txn, (void *)txn->mt_env, txn->mt_dbs[MAIN_DBI].md_root));
 	}
 	return rc;
 }
 
 int
 mdb_txn_begin(MDB_env *env, MDB_txn *parent, unsigned int flags, MDB_txn **ret)
 {
 	MDB_txn *txn;
 	MDB_ntxn *ntxn;
 	int rc, size, tsize;
 
 	flags &= MDB_TXN_BEGIN_FLAGS;
 	flags |= env->me_flags & MDB_WRITEMAP;
 
 	if (env->me_flags & MDB_RDONLY & ~flags) /* write txn in RDONLY env */
 		return EACCES;
 
 	if (parent) {
 		/* Nested transactions: Max 1 child, write txns only, no writemap */
 		flags |= parent->mt_flags;
 		if (flags & (MDB_RDONLY|MDB_WRITEMAP|MDB_TXN_BLOCKED)) {
 			return (parent->mt_flags & MDB_TXN_RDONLY) ? EINVAL : MDB_BAD_TXN;
 		}
 		/* Child txns save MDB_pgstate and use own copy of cursors */
 		size = env->me_maxdbs * (sizeof(MDB_db)+sizeof(MDB_cursor *)+1);
 		size += tsize = sizeof(MDB_ntxn);
 	} else if (flags & MDB_RDONLY) {
 		size = env->me_maxdbs * (sizeof(MDB_db)+1);
 		size += tsize = sizeof(MDB_txn);
 	} else {
 		/* Reuse preallocated write txn. However, do not touch it until
 		 * mdb_txn_renew0() succeeds, since it currently may be active.
 		 */
 		txn = env->me_txn0;
 		goto renew;
 	}
 	if ((txn = calloc(1, size)) == NULL) {
 		DPRINTF(("calloc: %s", strerror(errno)));
 		return ENOMEM;
 	}
 	txn->mt_dbxs = env->me_dbxs;	/* static */
 	txn->mt_dbs = (MDB_db *) ((char *)txn + tsize);
 	txn->mt_dbflags = (unsigned char *)txn + size - env->me_maxdbs;
 	txn->mt_flags = flags;
 	txn->mt_env = env;
 
 	if (parent) {
 		unsigned int i;
 		txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
 		txn->mt_dbiseqs = parent->mt_dbiseqs;
 		txn->mt_u.dirty_list = malloc(sizeof(MDB_ID2)*MDB_IDL_UM_SIZE);
 		if (!txn->mt_u.dirty_list ||
 			!(txn->mt_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)))
 		{
 			free(txn->mt_u.dirty_list);
 			free(txn);
 			return ENOMEM;
 		}
 		txn->mt_txnid = parent->mt_txnid;
 		txn->mt_dirty_room = parent->mt_dirty_room;
 		txn->mt_u.dirty_list[0].mid = 0;
 		txn->mt_spill_pgs = NULL;
 		txn->mt_next_pgno = parent->mt_next_pgno;
 		parent->mt_flags |= MDB_TXN_HAS_CHILD;
 		parent->mt_child = txn;
 		txn->mt_parent = parent;
 		txn->mt_numdbs = parent->mt_numdbs;
 		memcpy(txn->mt_dbs, parent->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
 		/* Copy parent's mt_dbflags, but clear DB_NEW */
 		for (i=0; i<txn->mt_numdbs; i++)
 			txn->mt_dbflags[i] = parent->mt_dbflags[i] & ~DB_NEW;
 		rc = 0;
 		ntxn = (MDB_ntxn *)txn;
 		ntxn->mnt_pgstate = env->me_pgstate; /* save parent me_pghead & co */
 		if (env->me_pghead) {
 			size = MDB_IDL_SIZEOF(env->me_pghead);
 			env->me_pghead = mdb_midl_alloc(env->me_pghead[0]);
 			if (env->me_pghead)
 				memcpy(env->me_pghead, ntxn->mnt_pgstate.mf_pghead, size);
 			else
 				rc = ENOMEM;
 		}
 		if (!rc)
 			rc = mdb_cursor_shadow(parent, txn);
 		if (rc)
 			mdb_txn_end(txn, MDB_END_FAIL_BEGINCHILD);
 	} else { /* MDB_RDONLY */
 		txn->mt_dbiseqs = env->me_dbiseqs;
 renew:
 		rc = mdb_txn_renew0(txn);
 	}
 	if (rc) {
 		if (txn != env->me_txn0)
 			free(txn);
 	} else {
 		txn->mt_flags |= flags;	/* could not change txn=me_txn0 earlier */
 		*ret = txn;
 		DPRINTF(("begin txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
 			txn->mt_txnid, (flags & MDB_RDONLY) ? 'r' : 'w',
 			(void *) txn, (void *) env, txn->mt_dbs[MAIN_DBI].md_root));
 	}
 
 	return rc;
 }
 
 MDB_env *
 mdb_txn_env(MDB_txn *txn)
 {
 	if(!txn) return NULL;
 	return txn->mt_env;
 }
 
 size_t
 mdb_txn_id(MDB_txn *txn)
 {
     if(!txn) return 0;
     return txn->mt_txnid;
 }
 
 /** Export or close DBI handles opened in this txn. */
 static void
 mdb_dbis_update(MDB_txn *txn, int keep)
 {
 	int i;
 	MDB_dbi n = txn->mt_numdbs;
 	MDB_env *env = txn->mt_env;
 	unsigned char *tdbflags = txn->mt_dbflags;
 
 	for (i = n; --i >= CORE_DBS;) {
 		if (tdbflags[i] & DB_NEW) {
 			if (keep) {
 				env->me_dbflags[i] = txn->mt_dbs[i].md_flags | MDB_VALID;
 			} else {
 				char *ptr = env->me_dbxs[i].md_name.mv_data;
 				if (ptr) {
 					env->me_dbxs[i].md_name.mv_data = NULL;
 					env->me_dbxs[i].md_name.mv_size = 0;
 					env->me_dbflags[i] = 0;
 					env->me_dbiseqs[i]++;
 					free(ptr);
 				}
 			}
 		}
 	}
 	if (keep && env->me_numdbs < n)
 		env->me_numdbs = n;
 }
 
 /** End a transaction, except successful commit of a nested transaction.
  * May be called twice for readonly txns: First reset it, then abort.
  * @param[in] txn the transaction handle to end
  * @param[in] mode why and how to end the transaction
  */
 static void
 mdb_txn_end(MDB_txn *txn, unsigned mode)
 {
 	MDB_env	*env = txn->mt_env;
 #if MDB_DEBUG
 	static const char *const names[] = MDB_END_NAMES;
 #endif
 
 	/* Export or close DBI handles opened in this txn */
 	mdb_dbis_update(txn, mode & MDB_END_UPDATE);
 
 	DPRINTF(("%s txn %"Z"u%c %p on mdbenv %p, root page %"Z"u",
 		names[mode & MDB_END_OPMASK],
 		txn->mt_txnid, (txn->mt_flags & MDB_TXN_RDONLY) ? 'r' : 'w',
 		(void *) txn, (void *)env, txn->mt_dbs[MAIN_DBI].md_root));
 
 	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
 		if (txn->mt_u.reader) {
 			txn->mt_u.reader->mr_txnid = (txnid_t)-1;
 			if (!(env->me_flags & MDB_NOTLS)) {
 				txn->mt_u.reader = NULL; /* txn does not own reader */
 			} else if (mode & MDB_END_SLOT) {
 				txn->mt_u.reader->mr_pid = 0;
 				txn->mt_u.reader = NULL;
 			} /* else txn owns the slot until it does MDB_END_SLOT */
 		}
 		txn->mt_numdbs = 0;		/* prevent further DBI activity */
 		txn->mt_flags |= MDB_TXN_FINISHED;
 
 	} else if (!F_ISSET(txn->mt_flags, MDB_TXN_FINISHED)) {
 		pgno_t *pghead = env->me_pghead;
 
 		if (!(mode & MDB_END_UPDATE)) /* !(already closed cursors) */
 			mdb_cursors_close(txn, 0);
 		if (!(env->me_flags & MDB_WRITEMAP)) {
 			mdb_dlist_free(txn);
 		}
 
 		txn->mt_numdbs = 0;
 		txn->mt_flags = MDB_TXN_FINISHED;
 
 		if (!txn->mt_parent) {
 			mdb_midl_shrink(&txn->mt_free_pgs);
 			env->me_free_pgs = txn->mt_free_pgs;
 			/* me_pgstate: */
 			env->me_pghead = NULL;
 			env->me_pglast = 0;
 
 			env->me_txn = NULL;
 			mode = 0;	/* txn == env->me_txn0, do not free() it */
 
 			/* The writer mutex was locked in mdb_txn_begin. */
 			if (env->me_txns)
 				UNLOCK_MUTEX(env->me_wmutex);
 		} else {
 			txn->mt_parent->mt_child = NULL;
 			txn->mt_parent->mt_flags &= ~MDB_TXN_HAS_CHILD;
 			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
 			mdb_midl_free(txn->mt_free_pgs);
 			free(txn->mt_u.dirty_list);
 		}
 		mdb_midl_free(txn->mt_spill_pgs);
 
 		mdb_midl_free(pghead);
 	}
 
 	if (mode & MDB_END_FREE)
 		free(txn);
 }
 
 void
 mdb_txn_reset(MDB_txn *txn)
 {
 	if (txn == NULL)
 		return;
 
 	/* This call is only valid for read-only txns */
 	if (!(txn->mt_flags & MDB_TXN_RDONLY))
 		return;
 
 	mdb_txn_end(txn, MDB_END_RESET);
 }
 
 void
 mdb_txn_abort(MDB_txn *txn)
 {
 	if (txn == NULL)
 		return;
 
 	if (txn->mt_child)
 		mdb_txn_abort(txn->mt_child);
 
 	mdb_txn_end(txn, MDB_END_ABORT|MDB_END_SLOT|MDB_END_FREE);
 }
 
 /** Save the freelist as of this transaction to the freeDB.
  * This changes the freelist. Keep trying until it stabilizes.
  */
 static int
 mdb_freelist_save(MDB_txn *txn)
 {
 	/* env->me_pghead[] can grow and shrink during this call.
 	 * env->me_pglast and txn->mt_free_pgs[] can only grow.
 	 * Page numbers cannot disappear from txn->mt_free_pgs[].
 	 */
 	MDB_cursor mc;
 	MDB_env	*env = txn->mt_env;
 	int rc, maxfree_1pg = env->me_maxfree_1pg, more = 1;
 	txnid_t	pglast = 0, head_id = 0;
 	pgno_t	freecnt = 0, *free_pgs, *mop;
 	ssize_t	head_room = 0, total_room = 0, mop_len, clean_limit;
 
 	mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
 
 	if (env->me_pghead) {
 		/* Make sure first page of freeDB is touched and on freelist */
 		rc = mdb_page_search(&mc, NULL, MDB_PS_FIRST|MDB_PS_MODIFY);
 		if (rc && rc != MDB_NOTFOUND)
 			return rc;
 	}
 
 	if (!env->me_pghead && txn->mt_loose_pgs) {
 		/* Put loose page numbers in mt_free_pgs, since
 		 * we may be unable to return them to me_pghead.
 		 */
 		MDB_page *mp = txn->mt_loose_pgs;
 		MDB_ID2 *dl = txn->mt_u.dirty_list;
 		unsigned x;
 		if ((rc = mdb_midl_need(&txn->mt_free_pgs, txn->mt_loose_count)) != 0)
 			return rc;
 		for (; mp; mp = NEXT_LOOSE_PAGE(mp)) {
 			mdb_midl_xappend(txn->mt_free_pgs, mp->mp_pgno);
 			/* must also remove from dirty list */
 			if (txn->mt_flags & MDB_TXN_WRITEMAP) {
 				for (x=1; x<=dl[0].mid; x++)
 					if (dl[x].mid == mp->mp_pgno)
 						break;
 				mdb_tassert(txn, x <= dl[0].mid);
 			} else {
 				x = mdb_mid2l_search(dl, mp->mp_pgno);
 				mdb_tassert(txn, dl[x].mid == mp->mp_pgno);
 				mdb_dpage_free(env, mp);
 			}
 			dl[x].mptr = NULL;
 		}
 		{
 			/* squash freed slots out of the dirty list */
 			unsigned y;
 			for (y=1; dl[y].mptr && y <= dl[0].mid; y++);
 			if (y <= dl[0].mid) {
 				for(x=y, y++;;) {
 					while (!dl[y].mptr && y <= dl[0].mid) y++;
 					if (y > dl[0].mid) break;
 					dl[x++] = dl[y++];
 				}
 				dl[0].mid = x-1;
 			} else {
 				/* all slots freed */
 				dl[0].mid = 0;
 			}
 		}
 		txn->mt_loose_pgs = NULL;
 		txn->mt_loose_count = 0;
 	}
 
 	/* MDB_RESERVE cancels meminit in ovpage malloc (when no WRITEMAP) */
 	clean_limit = (env->me_flags & (MDB_NOMEMINIT|MDB_WRITEMAP))
 		? SSIZE_MAX : maxfree_1pg;
 
 	for (;;) {
 		/* Come back here after each Put() in case freelist changed */
 		MDB_val key, data;
 		pgno_t *pgs;
 		ssize_t j;
 
 		/* If using records from freeDB which we have not yet
 		 * deleted, delete them and any we reserved for me_pghead.
 		 */
 		while (pglast < env->me_pglast) {
 			rc = mdb_cursor_first(&mc, &key, NULL);
 			if (rc)
 				return rc;
 			pglast = head_id = *(txnid_t *)key.mv_data;
 			total_room = head_room = 0;
 			mdb_tassert(txn, pglast <= env->me_pglast);
 			rc = mdb_cursor_del(&mc, 0);
 			if (rc)
 				return rc;
 		}
 
 		/* Save the IDL of pages freed by this txn, to a single record */
 		if (freecnt < txn->mt_free_pgs[0]) {
 			if (!freecnt) {
 				/* Make sure last page of freeDB is touched and on freelist */
 				rc = mdb_page_search(&mc, NULL, MDB_PS_LAST|MDB_PS_MODIFY);
 				if (rc && rc != MDB_NOTFOUND)
 					return rc;
 			}
 			free_pgs = txn->mt_free_pgs;
 			/* Write to last page of freeDB */
 			key.mv_size = sizeof(txn->mt_txnid);
 			key.mv_data = &txn->mt_txnid;
 			do {
 				freecnt = free_pgs[0];
 				data.mv_size = MDB_IDL_SIZEOF(free_pgs);
 				rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
 				if (rc)
 					return rc;
 				/* Retry if mt_free_pgs[] grew during the Put() */
 				free_pgs = txn->mt_free_pgs;
 			} while (freecnt < free_pgs[0]);
 			mdb_midl_sort(free_pgs);
 			memcpy(data.mv_data, free_pgs, data.mv_size);
 #if (MDB_DEBUG) > 1
 			{
 				unsigned int i = free_pgs[0];
 				DPRINTF(("IDL write txn %"Z"u root %"Z"u num %u",
 					txn->mt_txnid, txn->mt_dbs[FREE_DBI].md_root, i));
 				for (; i; i--)
 					DPRINTF(("IDL %"Z"u", free_pgs[i]));
 			}
 #endif
 			continue;
 		}
 
 		mop = env->me_pghead;
 		mop_len = (mop ? mop[0] : 0) + txn->mt_loose_count;
 
 		/* Reserve records for me_pghead[]. Split it if multi-page,
 		 * to avoid searching freeDB for a page range. Use keys in
 		 * range [1,me_pglast]: Smaller than txnid of oldest reader.
 		 */
 		if (total_room >= mop_len) {
 			if (total_room == mop_len || --more < 0)
 				break;
 		} else if (head_room >= maxfree_1pg && head_id > 1) {
 			/* Keep current record (overflow page), add a new one */
 			head_id--;
 			head_room = 0;
 		}
 		/* (Re)write {key = head_id, IDL length = head_room} */
 		total_room -= head_room;
 		head_room = mop_len - total_room;
 		if (head_room > maxfree_1pg && head_id > 1) {
 			/* Overflow multi-page for part of me_pghead */
 			head_room /= head_id; /* amortize page sizes */
 			head_room += maxfree_1pg - head_room % (maxfree_1pg + 1);
 		} else if (head_room < 0) {
 			/* Rare case, not bothering to delete this record */
 			head_room = 0;
 		}
 		key.mv_size = sizeof(head_id);
 		key.mv_data = &head_id;
 		data.mv_size = (head_room + 1) * sizeof(pgno_t);
 		rc = mdb_cursor_put(&mc, &key, &data, MDB_RESERVE);
 		if (rc)
 			return rc;
 		/* IDL is initially empty, zero out at least the length */
 		pgs = (pgno_t *)data.mv_data;
 		j = head_room > clean_limit ? head_room : 0;
 		do {
 			pgs[j] = 0;
 		} while (--j >= 0);
 		total_room += head_room;
 	}
 
 	/* Return loose page numbers to me_pghead, though usually none are
 	 * left at this point.  The pages themselves remain in dirty_list.
 	 */
 	if (txn->mt_loose_pgs) {
 		MDB_page *mp = txn->mt_loose_pgs;
 		unsigned count = txn->mt_loose_count;
 		MDB_IDL loose;
 		/* Room for loose pages + temp IDL with same */
 		if ((rc = mdb_midl_need(&env->me_pghead, 2*count+1)) != 0)
 			return rc;
 		mop = env->me_pghead;
 		loose = mop + MDB_IDL_ALLOCLEN(mop) - count;
 		for (count = 0; mp; mp = NEXT_LOOSE_PAGE(mp))
 			loose[ ++count ] = mp->mp_pgno;
 		loose[0] = count;
 		mdb_midl_sort(loose);
 		mdb_midl_xmerge(mop, loose);
 		txn->mt_loose_pgs = NULL;
 		txn->mt_loose_count = 0;
 		mop_len = mop[0];
 	}
 
 	/* Fill in the reserved me_pghead records */
 	rc = MDB_SUCCESS;
 	if (mop_len) {
 		MDB_val key, data;
 
 		mop += mop_len;
 		rc = mdb_cursor_first(&mc, &key, &data);
 		for (; !rc; rc = mdb_cursor_next(&mc, &key, &data, MDB_NEXT)) {
 			txnid_t id = *(txnid_t *)key.mv_data;
 			ssize_t	len = (ssize_t)(data.mv_size / sizeof(MDB_ID)) - 1;
 			MDB_ID save;
 
 			mdb_tassert(txn, len >= 0 && id <= env->me_pglast);
 			key.mv_data = &id;
 			if (len > mop_len) {
 				len = mop_len;
 				data.mv_size = (len + 1) * sizeof(MDB_ID);
 			}
 			data.mv_data = mop -= len;
 			save = mop[0];
 			mop[0] = len;
 			rc = mdb_cursor_put(&mc, &key, &data, MDB_CURRENT);
 			mop[0] = save;
 			if (rc || !(mop_len -= len))
 				break;
 		}
 	}
 	return rc;
 }
 
 /** Flush (some) dirty pages to the map, after clearing their dirty flag.
  * @param[in] txn the transaction that's being committed
  * @param[in] keep number of initial pages in dirty_list to keep dirty.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_flush(MDB_txn *txn, int keep)
 {
 	MDB_env		*env = txn->mt_env;
 	MDB_ID2L	dl = txn->mt_u.dirty_list;
 	unsigned	psize = env->me_psize, j;
 	int			i, pagecount = dl[0].mid, rc;
 	size_t		size = 0, pos = 0;
 	pgno_t		pgno = 0;
 	MDB_page	*dp = NULL;
 #ifdef _WIN32
 	OVERLAPPED	ov;
 #else
 	struct iovec iov[MDB_COMMIT_PAGES];
 	ssize_t		wpos = 0, wsize = 0, wres;
 	size_t		next_pos = 1; /* impossible pos, so pos != next_pos */
 	int			n = 0;
 #endif
 
 	j = i = keep;
 
 	if (env->me_flags & MDB_WRITEMAP) {
 		/* Clear dirty flags */
 		while (++i <= pagecount) {
 			dp = dl[i].mptr;
 			/* Don't flush this page yet */
 			if (dp->mp_flags & (P_LOOSE|P_KEEP)) {
 				dp->mp_flags &= ~P_KEEP;
 				dl[++j] = dl[i];
 				continue;
 			}
 			dp->mp_flags &= ~P_DIRTY;
 		}
 		goto done;
 	}
 
 	/* Write the pages */
 	for (;;) {
 		if (++i <= pagecount) {
 			dp = dl[i].mptr;
 			/* Don't flush this page yet */
 			if (dp->mp_flags & (P_LOOSE|P_KEEP)) {
 				dp->mp_flags &= ~P_KEEP;
 				dl[i].mid = 0;
 				continue;
 			}
 			pgno = dl[i].mid;
 			/* clear dirty flag */
 			dp->mp_flags &= ~P_DIRTY;
 			pos = pgno * psize;
 			size = psize;
 			if (IS_OVERFLOW(dp)) size *= dp->mp_pages;
 		}
 #ifdef _WIN32
 		else break;
 
 		/* Windows actually supports scatter/gather I/O, but only on
 		 * unbuffered file handles. Since we're relying on the OS page
 		 * cache for all our data, that's self-defeating. So we just
 		 * write pages one at a time. We use the ov structure to set
 		 * the write offset, to at least save the overhead of a Seek
 		 * system call.
 		 */
 		DPRINTF(("committing page %"Z"u", pgno));
 		memset(&ov, 0, sizeof(ov));
 		ov.Offset = pos & 0xffffffff;
 		ov.OffsetHigh = pos >> 16 >> 16;
 		if (!WriteFile(env->me_fd, dp, size, NULL, &ov)) {
 			rc = ErrCode();
 			DPRINTF(("WriteFile: %d", rc));
 			return rc;
 		}
 #else
 		/* Write up to MDB_COMMIT_PAGES dirty pages at a time. */
 		if (pos!=next_pos || n==MDB_COMMIT_PAGES || wsize+size>MAX_WRITE) {
 			if (n) {
 retry_write:
 				/* Write previous page(s) */
 #ifdef MDB_USE_PWRITEV
 				wres = pwritev(env->me_fd, iov, n, wpos);
 #else
 				if (n == 1) {
 					wres = pwrite(env->me_fd, iov[0].iov_base, wsize, wpos);
 				} else {
 retry_seek:
 					if (lseek(env->me_fd, wpos, SEEK_SET) == -1) {
 						rc = ErrCode();
 						if (rc == EINTR)
 							goto retry_seek;
 						DPRINTF(("lseek: %s", strerror(rc)));
 						return rc;
 					}
 					wres = writev(env->me_fd, iov, n);
 				}
 #endif
 				if (wres != wsize) {
 					if (wres < 0) {
 						rc = ErrCode();
 						if (rc == EINTR)
 							goto retry_write;
 						DPRINTF(("Write error: %s", strerror(rc)));
 					} else {
 						rc = EIO; /* TODO: Use which error code? */
 						DPUTS("short write, filesystem full?");
 					}
 					return rc;
 				}
 				n = 0;
 			}
 			if (i > pagecount)
 				break;
 			wpos = pos;
 			wsize = 0;
 		}
 		DPRINTF(("committing page %"Z"u", pgno));
 		next_pos = pos + size;
 		iov[n].iov_len = size;
 		iov[n].iov_base = (char *)dp;
 		wsize += size;
 		n++;
 #endif	/* _WIN32 */
 	}
 
 	/* MIPS has cache coherency issues, this is a no-op everywhere else
 	 * Note: for any size >= on-chip cache size, entire on-chip cache is
 	 * flushed.
 	 */
 	CACHEFLUSH(env->me_map, txn->mt_next_pgno * env->me_psize, DCACHE);
 
 	for (i = keep; ++i <= pagecount; ) {
 		dp = dl[i].mptr;
 		/* This is a page we skipped above */
 		if (!dl[i].mid) {
 			dl[++j] = dl[i];
 			dl[j].mid = dp->mp_pgno;
 			continue;
 		}
 		mdb_dpage_free(env, dp);
 	}
 
 done:
 	i--;
 	txn->mt_dirty_room += i - j;
 	dl[0].mid = j;
 	return MDB_SUCCESS;
 }
 
 int
 mdb_txn_commit(MDB_txn *txn)
 {
 	int		rc;
 	unsigned int i, end_mode;
 	MDB_env	*env;
 
 	if (txn == NULL)
 		return EINVAL;
 
 	/* mdb_txn_end() mode for a commit which writes nothing */
 	end_mode = MDB_END_EMPTY_COMMIT|MDB_END_UPDATE|MDB_END_SLOT|MDB_END_FREE;
 
 	if (txn->mt_child) {
 		rc = mdb_txn_commit(txn->mt_child);
 		if (rc)
 			goto fail;
 	}
 
 	env = txn->mt_env;
 
 	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY)) {
 		goto done;
 	}
 
 	if (txn->mt_flags & (MDB_TXN_FINISHED|MDB_TXN_ERROR)) {
 		DPUTS("txn has failed/finished, can't commit");
 		if (txn->mt_parent)
 			txn->mt_parent->mt_flags |= MDB_TXN_ERROR;
 		rc = MDB_BAD_TXN;
 		goto fail;
 	}
 
 	if (txn->mt_parent) {
 		MDB_txn *parent = txn->mt_parent;
 		MDB_page **lp;
 		MDB_ID2L dst, src;
 		MDB_IDL pspill;
 		unsigned x, y, len, ps_len;
 
 		/* Append our free list to parent's */
 		rc = mdb_midl_append_list(&parent->mt_free_pgs, txn->mt_free_pgs);
 		if (rc)
 			goto fail;
 		mdb_midl_free(txn->mt_free_pgs);
 		/* Failures after this must either undo the changes
 		 * to the parent or set MDB_TXN_ERROR in the parent.
 		 */
 
 		parent->mt_next_pgno = txn->mt_next_pgno;
 		parent->mt_flags = txn->mt_flags;
 
 		/* Merge our cursors into parent's and close them */
 		mdb_cursors_close(txn, 1);
 
 		/* Update parent's DB table. */
 		memcpy(parent->mt_dbs, txn->mt_dbs, txn->mt_numdbs * sizeof(MDB_db));
 		parent->mt_numdbs = txn->mt_numdbs;
 		parent->mt_dbflags[FREE_DBI] = txn->mt_dbflags[FREE_DBI];
 		parent->mt_dbflags[MAIN_DBI] = txn->mt_dbflags[MAIN_DBI];
 		for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
 			/* preserve parent's DB_NEW status */
 			x = parent->mt_dbflags[i] & DB_NEW;
 			parent->mt_dbflags[i] = txn->mt_dbflags[i] | x;
 		}
 
 		dst = parent->mt_u.dirty_list;
 		src = txn->mt_u.dirty_list;
 		/* Remove anything in our dirty list from parent's spill list */
 		if ((pspill = parent->mt_spill_pgs) && (ps_len = pspill[0])) {
 			x = y = ps_len;
 			pspill[0] = (pgno_t)-1;
 			/* Mark our dirty pages as deleted in parent spill list */
 			for (i=0, len=src[0].mid; ++i <= len; ) {
 				MDB_ID pn = src[i].mid << 1;
 				while (pn > pspill[x])
 					x--;
 				if (pn == pspill[x]) {
 					pspill[x] = 1;
 					y = --x;
 				}
 			}
 			/* Squash deleted pagenums if we deleted any */
 			for (x=y; ++x <= ps_len; )
 				if (!(pspill[x] & 1))
 					pspill[++y] = pspill[x];
 			pspill[0] = y;
 		}
 
 		/* Remove anything in our spill list from parent's dirty list */
 		if (txn->mt_spill_pgs && txn->mt_spill_pgs[0]) {
 			for (i=1; i<=txn->mt_spill_pgs[0]; i++) {
 				MDB_ID pn = txn->mt_spill_pgs[i];
 				if (pn & 1)
 					continue;	/* deleted spillpg */
 				pn >>= 1;
 				y = mdb_mid2l_search(dst, pn);
 				if (y <= dst[0].mid && dst[y].mid == pn) {
 					free(dst[y].mptr);
 					while (y < dst[0].mid) {
 						dst[y] = dst[y+1];
 						y++;
 					}
 					dst[0].mid--;
 				}
 			}
 		}
 
 		/* Find len = length of merging our dirty list with parent's */
 		x = dst[0].mid;
 		dst[0].mid = 0;		/* simplify loops */
 		if (parent->mt_parent) {
 			len = x + src[0].mid;
 			y = mdb_mid2l_search(src, dst[x].mid + 1) - 1;
 			for (i = x; y && i; y--) {
 				pgno_t yp = src[y].mid;
 				while (yp < dst[i].mid)
 					i--;
 				if (yp == dst[i].mid) {
 					i--;
 					len--;
 				}
 			}
 		} else { /* Simplify the above for single-ancestor case */
 			len = MDB_IDL_UM_MAX - txn->mt_dirty_room;
 		}
 		/* Merge our dirty list with parent's */
 		y = src[0].mid;
 		for (i = len; y; dst[i--] = src[y--]) {
 			pgno_t yp = src[y].mid;
 			while (yp < dst[x].mid)
 				dst[i--] = dst[x--];
 			if (yp == dst[x].mid)
 				free(dst[x--].mptr);
 		}
 		mdb_tassert(txn, i == x);
 		dst[0].mid = len;
 		free(txn->mt_u.dirty_list);
 		parent->mt_dirty_room = txn->mt_dirty_room;
 		if (txn->mt_spill_pgs) {
 			if (parent->mt_spill_pgs) {
 				/* TODO: Prevent failure here, so parent does not fail */
 				rc = mdb_midl_append_list(&parent->mt_spill_pgs, txn->mt_spill_pgs);
 				if (rc)
 					parent->mt_flags |= MDB_TXN_ERROR;
 				mdb_midl_free(txn->mt_spill_pgs);
 				mdb_midl_sort(parent->mt_spill_pgs);
 			} else {
 				parent->mt_spill_pgs = txn->mt_spill_pgs;
 			}
 		}
 
 		/* Append our loose page list to parent's */
 		for (lp = &parent->mt_loose_pgs; *lp; lp = &NEXT_LOOSE_PAGE(*lp))
 			;
 		*lp = txn->mt_loose_pgs;
 		parent->mt_loose_count += txn->mt_loose_count;
 
 		parent->mt_child = NULL;
 		mdb_midl_free(((MDB_ntxn *)txn)->mnt_pgstate.mf_pghead);
 		free(txn);
 		return rc;
 	}
 
 	if (txn != env->me_txn) {
 		DPUTS("attempt to commit unknown transaction");
 		rc = EINVAL;
 		goto fail;
 	}
 
 	mdb_cursors_close(txn, 0);
 
 	if (!txn->mt_u.dirty_list[0].mid &&
 		!(txn->mt_flags & (MDB_TXN_DIRTY|MDB_TXN_SPILLS)))
 		goto done;
 
 	DPRINTF(("committing txn %"Z"u %p on mdbenv %p, root page %"Z"u",
 	    txn->mt_txnid, (void*)txn, (void*)env, txn->mt_dbs[MAIN_DBI].md_root));
 
 	/* Update DB root pointers */
 	if (txn->mt_numdbs > CORE_DBS) {
 		MDB_cursor mc;
 		MDB_dbi i;
 		MDB_val data;
 		data.mv_size = sizeof(MDB_db);
 
 		mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
 		for (i = CORE_DBS; i < txn->mt_numdbs; i++) {
 			if (txn->mt_dbflags[i] & DB_DIRTY) {
 				if (TXN_DBI_CHANGED(txn, i)) {
 					rc = MDB_BAD_DBI;
 					goto fail;
 				}
 				data.mv_data = &txn->mt_dbs[i];
 				rc = mdb_cursor_put(&mc, &txn->mt_dbxs[i].md_name, &data,
 					F_SUBDATA);
 				if (rc)
 					goto fail;
 			}
 		}
 	}
 
 	rc = mdb_freelist_save(txn);
 	if (rc)
 		goto fail;
 
 	mdb_midl_free(env->me_pghead);
 	env->me_pghead = NULL;
 	mdb_midl_shrink(&txn->mt_free_pgs);
 
 #if (MDB_DEBUG) > 2
 	mdb_audit(txn);
 #endif
 
 	if ((rc = mdb_page_flush(txn, 0)) ||
 		(rc = mdb_env_sync(env, 0)) ||
 		(rc = mdb_env_write_meta(txn)))
 		goto fail;
 	end_mode = MDB_END_COMMITTED|MDB_END_UPDATE;
 
 done:
 	mdb_txn_end(txn, end_mode);
 	return MDB_SUCCESS;
 
 fail:
 	mdb_txn_abort(txn);
 	return rc;
 }
 
 /** Read the environment parameters of a DB environment before
  * mapping it into memory.
  * @param[in] env the environment handle
  * @param[out] meta address of where to store the meta information
  * @return 0 on success, non-zero on failure.
  */
 static int ESECT
 mdb_env_read_header(MDB_env *env, MDB_meta *meta)
 {
 	MDB_metabuf	pbuf;
 	MDB_page	*p;
 	MDB_meta	*m;
 	int			i, rc, off;
 	enum { Size = sizeof(pbuf) };
 
 	/* We don't know the page size yet, so use a minimum value.
 	 * Read both meta pages so we can use the latest one.
 	 */
 
 	for (i=off=0; i<NUM_METAS; i++, off += meta->mm_psize) {
 #ifdef _WIN32
 		DWORD len;
 		OVERLAPPED ov;
 		memset(&ov, 0, sizeof(ov));
 		ov.Offset = off;
 		rc = ReadFile(env->me_fd, &pbuf, Size, &len, &ov) ? (int)len : -1;
 		if (rc == -1 && ErrCode() == ERROR_HANDLE_EOF)
 			rc = 0;
 #else
 		rc = pread(env->me_fd, &pbuf, Size, off);
 #endif
 		if (rc != Size) {
 			if (rc == 0 && off == 0)
 				return ENOENT;
 			rc = rc < 0 ? (int) ErrCode() : MDB_INVALID;
 			DPRINTF(("read: %s", mdb_strerror(rc)));
 			return rc;
 		}
 
 		p = (MDB_page *)&pbuf;
 
 		if (!F_ISSET(p->mp_flags, P_META)) {
 			DPRINTF(("page %"Z"u not a meta page", p->mp_pgno));
 			return MDB_INVALID;
 		}
 
 		m = METADATA(p);
 		if (m->mm_magic != MDB_MAGIC) {
 			DPUTS("meta has invalid magic");
 			return MDB_INVALID;
 		}
 
 		if (m->mm_version != MDB_DATA_VERSION) {
 			DPRINTF(("database is version %u, expected version %u",
 				m->mm_version, MDB_DATA_VERSION));
 			return MDB_VERSION_MISMATCH;
 		}
 
 		if (off == 0 || m->mm_txnid > meta->mm_txnid)
 			*meta = *m;
 	}
 	return 0;
 }
 
 /** Fill in most of the zeroed #MDB_meta for an empty database environment */
 static void ESECT
 mdb_env_init_meta0(MDB_env *env, MDB_meta *meta)
 {
 	meta->mm_magic = MDB_MAGIC;
 	meta->mm_version = MDB_DATA_VERSION;
 	meta->mm_mapsize = env->me_mapsize;
 	meta->mm_psize = env->me_psize;
 	meta->mm_last_pg = NUM_METAS-1;
 	meta->mm_flags = env->me_flags & 0xffff;
 	meta->mm_flags |= MDB_INTEGERKEY; /* this is mm_dbs[FREE_DBI].md_flags */
 	meta->mm_dbs[FREE_DBI].md_root = P_INVALID;
 	meta->mm_dbs[MAIN_DBI].md_root = P_INVALID;
 }
 
 /** Write the environment parameters of a freshly created DB environment.
  * @param[in] env the environment handle
  * @param[in] meta the #MDB_meta to write
  * @return 0 on success, non-zero on failure.
  */
 static int ESECT
 mdb_env_init_meta(MDB_env *env, MDB_meta *meta)
 {
 	MDB_page *p, *q;
 	int rc;
 	unsigned int	 psize;
 #ifdef _WIN32
 	DWORD len;
 	OVERLAPPED ov;
 	memset(&ov, 0, sizeof(ov));
 #define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
 	ov.Offset = pos;	\
 	rc = WriteFile(fd, ptr, size, &len, &ov);	} while(0)
 #else
 	int len;
 #define DO_PWRITE(rc, fd, ptr, size, len, pos)	do { \
 	len = pwrite(fd, ptr, size, pos);	\
 	if (len == -1 && ErrCode() == EINTR) continue; \
 	rc = (len >= 0); break; } while(1)
 #endif
 
 	DPUTS("writing new meta page");
 
 	psize = env->me_psize;
 
 	p = calloc(NUM_METAS, psize);
 	if (!p)
 		return ENOMEM;
 
 	p->mp_pgno = 0;
 	p->mp_flags = P_META;
 	*(MDB_meta *)METADATA(p) = *meta;
 
 	q = (MDB_page *)((char *)p + psize);
 	q->mp_pgno = 1;
 	q->mp_flags = P_META;
 	*(MDB_meta *)METADATA(q) = *meta;
 
 	DO_PWRITE(rc, env->me_fd, p, psize * NUM_METAS, len, 0);
 	if (!rc)
 		rc = ErrCode();
 	else if ((unsigned) len == psize * NUM_METAS)
 		rc = MDB_SUCCESS;
 	else
 		rc = ENOSPC;
 	free(p);
 	return rc;
 }
 
 /** Update the environment info to commit a transaction.
  * @param[in] txn the transaction that's being committed
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_env_write_meta(MDB_txn *txn)
 {
 	MDB_env *env;
 	MDB_meta	meta, metab, *mp;
 	unsigned flags;
 	size_t mapsize;
 	off_t off;
 	int rc, len, toggle;
 	char *ptr;
 	HANDLE mfd;
 #ifdef _WIN32
 	OVERLAPPED ov;
 #else
 	int r2;
 #endif
 
 	toggle = txn->mt_txnid & 1;
 	DPRINTF(("writing meta page %d for root page %"Z"u",
 		toggle, txn->mt_dbs[MAIN_DBI].md_root));
 
 	env = txn->mt_env;
 	flags = env->me_flags;
 	mp = env->me_metas[toggle];
 	mapsize = env->me_metas[toggle ^ 1]->mm_mapsize;
 	/* Persist any increases of mapsize config */
 	if (mapsize < env->me_mapsize)
 		mapsize = env->me_mapsize;
 
 	if (flags & MDB_WRITEMAP) {
 		mp->mm_mapsize = mapsize;
 		mp->mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
 		mp->mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
 		mp->mm_last_pg = txn->mt_next_pgno - 1;
 #if (__GNUC__ * 100 + __GNUC_MINOR__ >= 404) && /* TODO: portability */	\
 	!(defined(__i386__) || defined(__x86_64__))
 		/* LY: issue a memory barrier, if not x86. ITS#7969 */
 		__sync_synchronize();
 #endif
 		mp->mm_txnid = txn->mt_txnid;
 		if (!(flags & (MDB_NOMETASYNC|MDB_NOSYNC))) {
 			unsigned meta_size = env->me_psize;
 			rc = (env->me_flags & MDB_MAPASYNC) ? MS_ASYNC : MS_SYNC;
 			ptr = (char *)mp - PAGEHDRSZ;
 #ifndef _WIN32	/* POSIX msync() requires ptr = start of OS page */
 			r2 = (ptr - env->me_map) & (env->me_os_psize - 1);
 			ptr -= r2;
 			meta_size += r2;
 #endif
 			if (MDB_MSYNC(ptr, meta_size, rc)) {
 				rc = ErrCode();
 				goto fail;
 			}
 		}
 		goto done;
 	}
 	metab.mm_txnid = mp->mm_txnid;
 	metab.mm_last_pg = mp->mm_last_pg;
 
 	meta.mm_mapsize = mapsize;
 	meta.mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
 	meta.mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
 	meta.mm_last_pg = txn->mt_next_pgno - 1;
 	meta.mm_txnid = txn->mt_txnid;
 
 	off = offsetof(MDB_meta, mm_mapsize);
 	ptr = (char *)&meta + off;
 	len = sizeof(MDB_meta) - off;
 	off += (char *)mp - env->me_map;
 
 	/* Write to the SYNC fd unless MDB_NOSYNC/MDB_NOMETASYNC.
 	 * (me_mfd goes to the same file as me_fd, but writing to it
 	 * also syncs to disk.  Avoids a separate fdatasync() call.)
 	 */
 	mfd = (flags & (MDB_NOSYNC|MDB_NOMETASYNC)) ? env->me_fd : env->me_mfd;
 #ifdef _WIN32
 	{
 		memset(&ov, 0, sizeof(ov));
 		ov.Offset = off;
 		if (!WriteFile(mfd, ptr, len, (DWORD *)&rc, &ov))
 			rc = -1;
 	}
 #else
 retry_write:
 	rc = pwrite(mfd, ptr, len, off);
 #endif
 	if (rc != len) {
 		rc = rc < 0 ? ErrCode() : EIO;
 #ifndef _WIN32
 		if (rc == EINTR)
 			goto retry_write;
 #endif
 		DPUTS("write failed, disk error?");
 		/* On a failure, the pagecache still contains the new data.
 		 * Write some old data back, to prevent it from being used.
 		 * Use the non-SYNC fd; we know it will fail anyway.
 		 */
 		meta.mm_last_pg = metab.mm_last_pg;
 		meta.mm_txnid = metab.mm_txnid;
 #ifdef _WIN32
 		memset(&ov, 0, sizeof(ov));
 		ov.Offset = off;
 		WriteFile(env->me_fd, ptr, len, NULL, &ov);
 #else
 		r2 = pwrite(env->me_fd, ptr, len, off);
 		(void)r2;	/* Silence warnings. We don't care about pwrite's return value */
 #endif
 fail:
 		env->me_flags |= MDB_FATAL_ERROR;
 		return rc;
 	}
 	/* MIPS has cache coherency issues, this is a no-op everywhere else */
 	CACHEFLUSH(env->me_map + off, len, DCACHE);
 done:
 	/* Memory ordering issues are irrelevant; since the entire writer
 	 * is wrapped by wmutex, all of these changes will become visible
 	 * after the wmutex is unlocked. Since the DB is multi-version,
 	 * readers will get consistent data regardless of how fresh or
 	 * how stale their view of these values is.
 	 */
 	if (env->me_txns)
 		env->me_txns->mti_txnid = txn->mt_txnid;
 
 	return MDB_SUCCESS;
 }
 
 /** Check both meta pages to see which one is newer.
  * @param[in] env the environment handle
  * @return newest #MDB_meta.
  */
 static MDB_meta *
 mdb_env_pick_meta(const MDB_env *env)
 {
 	MDB_meta *const *metas = env->me_metas;
 	return metas[ metas[0]->mm_txnid < metas[1]->mm_txnid ];
 }
 
 int ESECT
 mdb_env_create(MDB_env **env)
 {
 	MDB_env *e;
 
 	e = calloc(1, sizeof(MDB_env));
 	if (!e)
 		return ENOMEM;
 
 	e->me_maxreaders = DEFAULT_READERS;
 	e->me_maxdbs = e->me_numdbs = CORE_DBS;
 	e->me_fd = INVALID_HANDLE_VALUE;
 	e->me_lfd = INVALID_HANDLE_VALUE;
 	e->me_mfd = INVALID_HANDLE_VALUE;
 #ifdef MDB_USE_POSIX_SEM
 	e->me_rmutex = SEM_FAILED;
 	e->me_wmutex = SEM_FAILED;
 #endif
 	e->me_pid = getpid();
 	GET_PAGESIZE(e->me_os_psize);
 	VGMEMP_CREATE(e,0,0);
 	*env = e;
 	return MDB_SUCCESS;
 }
 
 static int ESECT
 mdb_env_map(MDB_env *env, void *addr)
 {
 	MDB_page *p;
 	unsigned int flags = env->me_flags;
 #ifdef _WIN32
 	int rc;
 	HANDLE mh;
 	LONG sizelo, sizehi;
 	size_t msize;
 
 	if (flags & MDB_RDONLY) {
 		/* Don't set explicit map size, use whatever exists */
 		msize = 0;
 		sizelo = 0;
 		sizehi = 0;
 	} else {
 		msize = env->me_mapsize;
 		sizelo = msize & 0xffffffff;
 		sizehi = msize >> 16 >> 16; /* only needed on Win64 */
 
 		/* Windows won't create mappings for zero length files.
 		 * and won't map more than the file size.
 		 * Just set the maxsize right now.
 		 */
 		if (!(flags & MDB_WRITEMAP) && (SetFilePointer(env->me_fd, sizelo, &sizehi, 0) != (DWORD)sizelo
 			|| !SetEndOfFile(env->me_fd)
 			|| SetFilePointer(env->me_fd, 0, NULL, 0) != 0))
 			return ErrCode();
 	}
 
 	mh = CreateFileMapping(env->me_fd, NULL, flags & MDB_WRITEMAP ?
 		PAGE_READWRITE : PAGE_READONLY,
 		sizehi, sizelo, NULL);
 	if (!mh)
 		return ErrCode();
 	env->me_map = MapViewOfFileEx(mh, flags & MDB_WRITEMAP ?
 		FILE_MAP_WRITE : FILE_MAP_READ,
 		0, 0, msize, addr);
 	rc = env->me_map ? 0 : ErrCode();
 	CloseHandle(mh);
 	if (rc)
 		return rc;
 #else
 	int mmap_flags = MAP_SHARED;
 	int prot = PROT_READ;
 #ifdef MAP_NOSYNC	/* Used on FreeBSD */
 	if (flags & MDB_NOSYNC)
 		mmap_flags |= MAP_NOSYNC;
 #endif
 	if (flags & MDB_WRITEMAP) {
 		prot |= PROT_WRITE;
 		if (ftruncate(env->me_fd, env->me_mapsize) < 0)
 			return ErrCode();
 	}
 	env->me_map = mmap(addr, env->me_mapsize, prot, mmap_flags,
 		env->me_fd, 0);
 	if (env->me_map == MAP_FAILED) {
 		env->me_map = NULL;
 		return ErrCode();
 	}
 
 	if (flags & MDB_NORDAHEAD) {
 		/* Turn off readahead. It's harmful when the DB is larger than RAM. */
 #ifdef MADV_RANDOM
 		madvise(env->me_map, env->me_mapsize, MADV_RANDOM);
 #else
 #ifdef POSIX_MADV_RANDOM
 		posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_RANDOM);
 #endif /* POSIX_MADV_RANDOM */
 #endif /* MADV_RANDOM */
 	}
 #endif /* _WIN32 */
 
 	/* Can happen because the address argument to mmap() is just a
 	 * hint.  mmap() can pick another, e.g. if the range is in use.
 	 * The MAP_FIXED flag would prevent that, but then mmap could
 	 * instead unmap existing pages to make room for the new map.
 	 */
 	if (addr && env->me_map != addr)
 		return EBUSY;	/* TODO: Make a new MDB_* error code? */
 
 	p = (MDB_page *)env->me_map;
 	env->me_metas[0] = METADATA(p);
 	env->me_metas[1] = (MDB_meta *)((char *)env->me_metas[0] + env->me_psize);
 
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_set_mapsize(MDB_env *env, size_t size)
 {
 	/* If env is already open, caller is responsible for making
 	 * sure there are no active txns.
 	 */
 	if (env->me_map) {
 		int rc;
 		MDB_meta *meta;
 		void *old;
 		if (env->me_txn)
 			return EINVAL;
 		meta = mdb_env_pick_meta(env);
 		if (!size)
 			size = meta->mm_mapsize;
 		{
 			/* Silently round up to minimum if the size is too small */
 			size_t minsize = (meta->mm_last_pg + 1) * env->me_psize;
 			if (size < minsize)
 				size = minsize;
 		}
 		munmap(env->me_map, env->me_mapsize);
 		env->me_mapsize = size;
 		old = (env->me_flags & MDB_FIXEDMAP) ? env->me_map : NULL;
 		rc = mdb_env_map(env, old);
 		if (rc)
 			return rc;
 	}
 	env->me_mapsize = size;
 	if (env->me_psize)
 		env->me_maxpg = env->me_mapsize / env->me_psize;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_set_maxdbs(MDB_env *env, MDB_dbi dbs)
 {
 	if (env->me_map)
 		return EINVAL;
 	env->me_maxdbs = dbs + CORE_DBS;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_set_maxreaders(MDB_env *env, unsigned int readers)
 {
 	if (env->me_map || readers < 1)
 		return EINVAL;
 	env->me_maxreaders = readers;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_get_maxreaders(MDB_env *env, unsigned int *readers)
 {
 	if (!env || !readers)
 		return EINVAL;
 	*readers = env->me_maxreaders;
 	return MDB_SUCCESS;
 }
 
 static int ESECT
 mdb_fsize(HANDLE fd, size_t *size)
 {
 #ifdef _WIN32
 	LARGE_INTEGER fsize;
 
 	if (!GetFileSizeEx(fd, &fsize))
 		return ErrCode();
 
 	*size = fsize.QuadPart;
 #else
 	struct stat st;
 
 	if (fstat(fd, &st))
 		return ErrCode();
 
 	*size = st.st_size;
 #endif
 	return MDB_SUCCESS;
 }
 
 
 #ifdef _WIN32
 typedef wchar_t	mdb_nchar_t;
 # define MDB_NAME(str)	L##str
 # define mdb_name_cpy	wcscpy
 #else
 /** Character type for file names: char on Unix, wchar_t on Windows */
 typedef char	mdb_nchar_t;
 # define MDB_NAME(str)	str		/**< #mdb_nchar_t[] string literal */
 # define mdb_name_cpy	strcpy	/**< Copy name (#mdb_nchar_t string) */
 #endif
 
 /** Filename - string of #mdb_nchar_t[] */
 typedef struct MDB_name {
 	int mn_len;					/**< Length  */
 	int mn_alloced;				/**< True if #mn_val was malloced */
 	mdb_nchar_t	*mn_val;		/**< Contents */
 } MDB_name;
 
 /** Filename suffixes [datafile,lockfile][without,with MDB_NOSUBDIR] */
 static const mdb_nchar_t *const mdb_suffixes[2][2] = {
 	{ MDB_NAME("/data.mdb"), MDB_NAME("")      },
 	{ MDB_NAME("/lock.mdb"), MDB_NAME("-lock") }
 };
 
 #define MDB_SUFFLEN 9	/**< Max string length in #mdb_suffixes[] */
 
 /** Set up filename + scratch area for filename suffix, for opening files.
  * It should be freed with #mdb_fname_destroy().
  * On Windows, paths are converted from char *UTF-8 to wchar_t *UTF-16.
  *
  * @param[in] path Pathname for #mdb_env_open().
  * @param[in] envflags Whether a subdir and/or lockfile will be used.
  * @param[out] fname Resulting filename, with room for a suffix if necessary.
  */
 static int ESECT
 mdb_fname_init(const char *path, unsigned envflags, MDB_name *fname)
 {
 	int no_suffix = F_ISSET(envflags, MDB_NOSUBDIR|MDB_NOLOCK);
 	fname->mn_alloced = 0;
 #ifdef _WIN32
 	return utf8_to_utf16(path, fname, no_suffix ? 0 : MDB_SUFFLEN);
 #else
 	fname->mn_len = strlen(path);
 	if (no_suffix)
 		fname->mn_val = (char *) path;
 	else if ((fname->mn_val = malloc(fname->mn_len + MDB_SUFFLEN+1)) != NULL) {
 		fname->mn_alloced = 1;
 		strcpy(fname->mn_val, path);
 	}
 	else
 		return ENOMEM;
 	return MDB_SUCCESS;
 #endif
 }
 
 /** Destroy \b fname from #mdb_fname_init() */
 #define mdb_fname_destroy(fname) \
 	do { if ((fname).mn_alloced) free((fname).mn_val); } while (0)
 
 #ifdef O_CLOEXEC /* POSIX.1-2008: Set FD_CLOEXEC atomically at open() */
 # define MDB_CLOEXEC		O_CLOEXEC
 #else
 # define MDB_CLOEXEC		0
 #endif
 
 /** File type, access mode etc. for #mdb_fopen() */
 enum mdb_fopen_type {
 #ifdef _WIN32
 	MDB_O_RDONLY, MDB_O_RDWR, MDB_O_META, MDB_O_COPY, MDB_O_LOCKS
 #else
 	/* A comment in mdb_fopen() explains some O_* flag choices. */
 	MDB_O_RDONLY= O_RDONLY,                            /**< for RDONLY me_fd */
 	MDB_O_RDWR  = O_RDWR  |O_CREAT,                    /**< for me_fd */
 	MDB_O_META  = O_WRONLY|MDB_DSYNC     |MDB_CLOEXEC, /**< for me_mfd */
 	MDB_O_COPY  = O_WRONLY|O_CREAT|O_EXCL|MDB_CLOEXEC, /**< for #mdb_env_copy() */
 	/** Bitmask for open() flags in enum #mdb_fopen_type.  The other bits
 	 * distinguish otherwise-equal MDB_O_* constants from each other.
 	 */
 	MDB_O_MASK  = MDB_O_RDWR|MDB_CLOEXEC | MDB_O_RDONLY|MDB_O_META|MDB_O_COPY,
 	MDB_O_LOCKS = MDB_O_RDWR|MDB_CLOEXEC | ((MDB_O_MASK+1) & ~MDB_O_MASK) /**< for me_lfd */
 #endif
 };
 
 /** Open an LMDB file.
  * @param[in] env	The LMDB environment.
  * @param[in,out] fname	Path from from #mdb_fname_init().  A suffix is
  * appended if necessary to create the filename, without changing mn_len.
  * @param[in] which	Determines file type, access mode, etc.
  * @param[in] mode	The Unix permissions for the file, if we create it.
  * @param[out] res	Resulting file handle.
  * @return 0 on success, non-zero on failure.
  */
 static int ESECT
 mdb_fopen(const MDB_env *env, MDB_name *fname,
 	enum mdb_fopen_type which, mdb_mode_t mode,
 	HANDLE *res)
 {
 	int rc = MDB_SUCCESS;
 	HANDLE fd;
 #ifdef _WIN32
 	DWORD acc, share, disp, attrs;
 #else
 	int flags;
 #endif
 
 	if (fname->mn_alloced)		/* modifiable copy */
 		mdb_name_cpy(fname->mn_val + fname->mn_len,
 			mdb_suffixes[which==MDB_O_LOCKS][F_ISSET(env->me_flags, MDB_NOSUBDIR)]);
 
 	/* The directory must already exist.  Usually the file need not.
 	 * MDB_O_META requires the file because we already created it using
 	 * MDB_O_RDWR.  MDB_O_COPY must not overwrite an existing file.
 	 *
 	 * With MDB_O_COPY we do not want the OS to cache the writes, since
 	 * the source data is already in the OS cache.
 	 *
 	 * The lockfile needs FD_CLOEXEC (close file descriptor on exec*())
 	 * to avoid the flock() issues noted under Caveats in lmdb.h.
 	 * Also set it for other filehandles which the user cannot get at
 	 * and close himself, which he may need after fork().  I.e. all but
 	 * me_fd, which programs do use via mdb_env_get_fd().
 	 */
 
 #ifdef _WIN32
 	acc = GENERIC_READ|GENERIC_WRITE;
 	share = FILE_SHARE_READ|FILE_SHARE_WRITE;
 	disp = OPEN_ALWAYS;
 	attrs = FILE_ATTRIBUTE_NORMAL;
 	switch (which) {
 	case MDB_O_RDONLY:			/* read-only datafile */
 		acc = GENERIC_READ;
 		disp = OPEN_EXISTING;
 		break;
 	case MDB_O_META:			/* for writing metapages */
 		acc = GENERIC_WRITE;
 		disp = OPEN_EXISTING;
 		attrs = FILE_ATTRIBUTE_NORMAL|FILE_FLAG_WRITE_THROUGH;
 		break;
 	case MDB_O_COPY:			/* mdb_env_copy() & co */
 		acc = GENERIC_WRITE;
 		share = 0;
 		disp = CREATE_NEW;
 		attrs = FILE_FLAG_NO_BUFFERING|FILE_FLAG_WRITE_THROUGH;
 		break;
 	default: break;	/* silence gcc -Wswitch (not all enum values handled) */
 	}
 	fd = CreateFileW(fname->mn_val, acc, share, NULL, disp, attrs, NULL);
 #else
 	fd = open(fname->mn_val, which & MDB_O_MASK, mode);
 #endif
 
 	if (fd == INVALID_HANDLE_VALUE)
 		rc = ErrCode();
 #ifndef _WIN32
 	else {
 		if (which != MDB_O_RDONLY && which != MDB_O_RDWR) {
 			/* Set CLOEXEC if we could not pass it to open() */
 			if (!MDB_CLOEXEC && (flags = fcntl(fd, F_GETFD)) != -1)
 				(void) fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 		}
 		if (which == MDB_O_COPY && env->me_psize >= env->me_os_psize) {
 			/* This may require buffer alignment.  There is no portable
 			 * way to ask how much, so we require OS pagesize alignment.
 			 */
 # ifdef F_NOCACHE	/* __APPLE__ */
 			(void) fcntl(fd, F_NOCACHE, 1);
 # elif defined O_DIRECT
 			/* open(...O_DIRECT...) would break on filesystems without
 			 * O_DIRECT support (ITS#7682). Try to set it here instead.
 			 */
 			if ((flags = fcntl(fd, F_GETFL)) != -1)
 				(void) fcntl(fd, F_SETFL, flags | O_DIRECT);
 # endif
 		}
 	}
 #endif	/* !_WIN32 */
 
 	*res = fd;
 	return rc;
 }
 
 
 #ifdef BROKEN_FDATASYNC
 #include <sys/utsname.h>
 #include <sys/vfs.h>
 #endif
 
 /** Further setup required for opening an LMDB environment
  */
 static int ESECT
 mdb_env_open2(MDB_env *env)
 {
 	unsigned int flags = env->me_flags;
 	int i, newenv = 0, rc;
 	MDB_meta meta;
 
 #ifdef _WIN32
 	/* See if we should use QueryLimited */
 	rc = GetVersion();
 	if ((rc & 0xff) > 5)
 		env->me_pidquery = MDB_PROCESS_QUERY_LIMITED_INFORMATION;
 	else
 		env->me_pidquery = PROCESS_QUERY_INFORMATION;
 #endif /* _WIN32 */
 
 #ifdef BROKEN_FDATASYNC
 	/* ext3/ext4 fdatasync is broken on some older Linux kernels.
 	 * https://lkml.org/lkml/2012/9/3/83
 	 * Kernels after 3.6-rc6 are known good.
 	 * https://lkml.org/lkml/2012/9/10/556
 	 * See if the DB is on ext3/ext4, then check for new enough kernel
 	 * Kernels 2.6.32.60, 2.6.34.15, 3.2.30, and 3.5.4 are also known
 	 * to be patched.
 	 */
 	{
 		struct statfs st;
 		fstatfs(env->me_fd, &st);
 		while (st.f_type == 0xEF53) {
 			struct utsname uts;
 			int i;
 			uname(&uts);
 			if (uts.release[0] < '3') {
 				if (!strncmp(uts.release, "2.6.32.", 7)) {
 					i = atoi(uts.release+7);
 					if (i >= 60)
 						break;	/* 2.6.32.60 and newer is OK */
 				} else if (!strncmp(uts.release, "2.6.34.", 7)) {
 					i = atoi(uts.release+7);
 					if (i >= 15)
 						break;	/* 2.6.34.15 and newer is OK */
 				}
 			} else if (uts.release[0] == '3') {
 				i = atoi(uts.release+2);
 				if (i > 5)
 					break;	/* 3.6 and newer is OK */
 				if (i == 5) {
 					i = atoi(uts.release+4);
 					if (i >= 4)
 						break;	/* 3.5.4 and newer is OK */
 				} else if (i == 2) {
 					i = atoi(uts.release+4);
 					if (i >= 30)
 						break;	/* 3.2.30 and newer is OK */
 				}
 			} else {	/* 4.x and newer is OK */
 				break;
 			}
 			env->me_flags |= MDB_FSYNCONLY;
 			break;
 		}
 	}
 #endif
 
 	if ((i = mdb_env_read_header(env, &meta)) != 0) {
 		if (i != ENOENT)
 			return i;
 		DPUTS("new mdbenv");
 		newenv = 1;
 		env->me_psize = env->me_os_psize;
 		if (env->me_psize > MAX_PAGESIZE)
 			env->me_psize = MAX_PAGESIZE;
 		memset(&meta, 0, sizeof(meta));
 		mdb_env_init_meta0(env, &meta);
 		meta.mm_mapsize = DEFAULT_MAPSIZE;
 	} else {
 		env->me_psize = meta.mm_psize;
 	}
 
 	/* Was a mapsize configured? */
 	if (!env->me_mapsize) {
 		env->me_mapsize = meta.mm_mapsize;
 	}
 	{
 		/* Make sure mapsize >= committed data size.  Even when using
 		 * mm_mapsize, which could be broken in old files (ITS#7789).
 		 */
 		size_t minsize = (meta.mm_last_pg + 1) * meta.mm_psize;
 		if (env->me_mapsize < minsize)
 			env->me_mapsize = minsize;
 	}
 	meta.mm_mapsize = env->me_mapsize;
 
 	if (newenv && !(flags & MDB_FIXEDMAP)) {
 		/* mdb_env_map() may grow the datafile.  Write the metapages
 		 * first, so the file will be valid if initialization fails.
 		 * Except with FIXEDMAP, since we do not yet know mm_address.
 		 * We could fill in mm_address later, but then a different
 		 * program might end up doing that - one with a memory layout
 		 * and map address which does not suit the main program.
 		 */
 		rc = mdb_env_init_meta(env, &meta);
 		if (rc)
 			return rc;
 		newenv = 0;
 	}
 
 	rc = mdb_env_map(env, (flags & MDB_FIXEDMAP) ? meta.mm_address : NULL);
 	if (rc)
 		return rc;
 
 	if (newenv) {
 		if (flags & MDB_FIXEDMAP)
 			meta.mm_address = env->me_map;
 		i = mdb_env_init_meta(env, &meta);
 		if (i != MDB_SUCCESS) {
 			return i;
 		}
 	}
 
 	env->me_maxfree_1pg = (env->me_psize - PAGEHDRSZ) / sizeof(pgno_t) - 1;
 	env->me_nodemax = (((env->me_psize - PAGEHDRSZ) / MDB_MINKEYS) & -2)
 		- sizeof(indx_t);
 #if !(MDB_MAXKEYSIZE)
 	env->me_maxkey = env->me_nodemax - (NODESIZE + sizeof(MDB_db));
 #endif
 	env->me_maxpg = env->me_mapsize / env->me_psize;
 
 #if MDB_DEBUG
 	{
 		MDB_meta *meta = mdb_env_pick_meta(env);
 		MDB_db *db = &meta->mm_dbs[MAIN_DBI];
 
 		DPRINTF(("opened database version %u, pagesize %u",
 			meta->mm_version, env->me_psize));
 		DPRINTF(("using meta page %d",    (int) (meta->mm_txnid & 1)));
 		DPRINTF(("depth: %u",             db->md_depth));
 		DPRINTF(("entries: %"Z"u",        db->md_entries));
 		DPRINTF(("branch pages: %"Z"u",   db->md_branch_pages));
 		DPRINTF(("leaf pages: %"Z"u",     db->md_leaf_pages));
 		DPRINTF(("overflow pages: %"Z"u", db->md_overflow_pages));
 		DPRINTF(("root: %"Z"u",           db->md_root));
 	}
 #endif
 
 	return MDB_SUCCESS;
 }
 
 
 /** Release a reader thread's slot in the reader lock table.
  *	This function is called automatically when a thread exits.
  * @param[in] ptr This points to the slot in the reader lock table.
  */
 static void
 mdb_env_reader_dest(void *ptr)
 {
 	MDB_reader *reader = ptr;
 
 #ifndef _WIN32
 	if (reader->mr_pid == getpid()) /* catch pthread_exit() in child process */
 #endif
 		/* We omit the mutex, so do this atomically (i.e. skip mr_txnid) */
 		reader->mr_pid = 0;
 }
 
 #ifdef _WIN32
 /** Junk for arranging thread-specific callbacks on Windows. This is
  *	necessarily platform and compiler-specific. Windows supports up
  *	to 1088 keys. Let's assume nobody opens more than 64 environments
  *	in a single process, for now. They can override this if needed.
  */
 #ifndef MAX_TLS_KEYS
 #define MAX_TLS_KEYS	64
 #endif
 static pthread_key_t mdb_tls_keys[MAX_TLS_KEYS];
 static int mdb_tls_nkeys;
 
 static void NTAPI mdb_tls_callback(PVOID module, DWORD reason, PVOID ptr)
 {
 	int i;
 	switch(reason) {
 	case DLL_PROCESS_ATTACH: break;
 	case DLL_THREAD_ATTACH: break;
 	case DLL_THREAD_DETACH:
 		for (i=0; i<mdb_tls_nkeys; i++) {
 			MDB_reader *r = pthread_getspecific(mdb_tls_keys[i]);
 			if (r) {
 				mdb_env_reader_dest(r);
 			}
 		}
 		break;
 	case DLL_PROCESS_DETACH: break;
 	}
 }
 #ifdef __GNUC__
 #ifdef _WIN64
 const PIMAGE_TLS_CALLBACK mdb_tls_cbp __attribute__((section (".CRT$XLB"))) = mdb_tls_callback;
 #else
 PIMAGE_TLS_CALLBACK mdb_tls_cbp __attribute__((section (".CRT$XLB"))) = mdb_tls_callback;
 #endif
 #else
 #ifdef _WIN64
 /* Force some symbol references.
  *	_tls_used forces the linker to create the TLS directory if not already done
  *	mdb_tls_cbp prevents whole-program-optimizer from dropping the symbol.
  */
 #pragma comment(linker, "/INCLUDE:_tls_used")
 #pragma comment(linker, "/INCLUDE:mdb_tls_cbp")
 #pragma const_seg(".CRT$XLB")
 extern const PIMAGE_TLS_CALLBACK mdb_tls_cbp;
 const PIMAGE_TLS_CALLBACK mdb_tls_cbp = mdb_tls_callback;
 #pragma const_seg()
 #else	/* _WIN32 */
 #pragma comment(linker, "/INCLUDE:__tls_used")
 #pragma comment(linker, "/INCLUDE:_mdb_tls_cbp")
 #pragma data_seg(".CRT$XLB")
 PIMAGE_TLS_CALLBACK mdb_tls_cbp = mdb_tls_callback;
 #pragma data_seg()
 #endif	/* WIN 32/64 */
 #endif	/* !__GNUC__ */
 #endif
 
 /** Downgrade the exclusive lock on the region back to shared */
 static int ESECT
 mdb_env_share_locks(MDB_env *env, int *excl)
 {
 	int rc = 0;
 	MDB_meta *meta = mdb_env_pick_meta(env);
 
 	env->me_txns->mti_txnid = meta->mm_txnid;
 
 #ifdef _WIN32
 	{
 		OVERLAPPED ov;
 		/* First acquire a shared lock. The Unlock will
 		 * then release the existing exclusive lock.
 		 */
 		memset(&ov, 0, sizeof(ov));
 		if (!LockFileEx(env->me_lfd, 0, 0, 1, 0, &ov)) {
 			rc = ErrCode();
 		} else {
 			UnlockFile(env->me_lfd, 0, 0, 1, 0);
 			*excl = 0;
 		}
 	}
 #else
 	{
 		struct flock lock_info;
 		/* The shared lock replaces the existing lock */
 		memset((void *)&lock_info, 0, sizeof(lock_info));
 		lock_info.l_type = F_RDLCK;
 		lock_info.l_whence = SEEK_SET;
 		lock_info.l_start = 0;
 		lock_info.l_len = 1;
 		while ((rc = fcntl(env->me_lfd, F_SETLK, &lock_info)) &&
 				(rc = ErrCode()) == EINTR) ;
 		*excl = rc ? -1 : 0;	/* error may mean we lost the lock */
 	}
 #endif
 
 	return rc;
 }
 
 /** Try to get exclusive lock, otherwise shared.
  *	Maintain *excl = -1: no/unknown lock, 0: shared, 1: exclusive.
  */
 static int ESECT
 mdb_env_excl_lock(MDB_env *env, int *excl)
 {
 	int rc = 0;
 #ifdef _WIN32
 	if (LockFile(env->me_lfd, 0, 0, 1, 0)) {
 		*excl = 1;
 	} else {
 		OVERLAPPED ov;
 		memset(&ov, 0, sizeof(ov));
 		if (LockFileEx(env->me_lfd, 0, 0, 1, 0, &ov)) {
 			*excl = 0;
 		} else {
 			rc = ErrCode();
 		}
 	}
 #else
 	struct flock lock_info;
 	memset((void *)&lock_info, 0, sizeof(lock_info));
 	lock_info.l_type = F_WRLCK;
 	lock_info.l_whence = SEEK_SET;
 	lock_info.l_start = 0;
 	lock_info.l_len = 1;
 	while ((rc = fcntl(env->me_lfd, F_SETLK, &lock_info)) &&
 			(rc = ErrCode()) == EINTR) ;
 	if (!rc) {
 		*excl = 1;
 	} else
 # ifndef MDB_USE_POSIX_MUTEX
 	if (*excl < 0) /* always true when MDB_USE_POSIX_MUTEX */
 # endif
 	{
 		lock_info.l_type = F_RDLCK;
 		while ((rc = fcntl(env->me_lfd, F_SETLKW, &lock_info)) &&
 				(rc = ErrCode()) == EINTR) ;
 		if (rc == 0)
 			*excl = 0;
 	}
 #endif
 	return rc;
 }
 
 #ifdef MDB_USE_HASH
 /*
  * hash_64 - 64 bit Fowler/Noll/Vo-0 FNV-1a hash code
  *
  * @(#) $Revision: 5.1 $
  * @(#) $Id: hash_64a.c,v 5.1 2009/06/30 09:01:38 chongo Exp $
  * @(#) $Source: /usr/local/src/cmd/fnv/RCS/hash_64a.c,v $
  *
  *	  http://www.isthe.com/chongo/tech/comp/fnv/index.html
  *
  ***
  *
  * Please do not copyright this code.  This code is in the public domain.
  *
  * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
  * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
  * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
  * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  * PERFORMANCE OF THIS SOFTWARE.
  *
  * By:
  *	chongo <Landon Curt Noll> /\oo/\
  *	  http://www.isthe.com/chongo/
  *
  * Share and Enjoy!	:-)
  */
 
 typedef unsigned long long	mdb_hash_t;
 #define MDB_HASH_INIT ((mdb_hash_t)0xcbf29ce484222325ULL)
 
 /** perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
  * @param[in] val	value to hash
  * @param[in] hval	initial value for hash
  * @return 64 bit hash
  *
  * NOTE: To use the recommended 64 bit FNV-1a hash, use MDB_HASH_INIT as the
  * 	 hval arg on the first call.
  */
 static mdb_hash_t
 mdb_hash_val(MDB_val *val, mdb_hash_t hval)
 {
 	unsigned char *s = (unsigned char *)val->mv_data;	/* unsigned string */
 	unsigned char *end = s + val->mv_size;
 	/*
 	 * FNV-1a hash each octet of the string
 	 */
 	while (s < end) {
 		/* xor the bottom with the current octet */
 		hval ^= (mdb_hash_t)*s++;
 
 		/* multiply by the 64 bit FNV magic prime mod 2^64 */
 		hval += (hval << 1) + (hval << 4) + (hval << 5) +
 			(hval << 7) + (hval << 8) + (hval << 40);
 	}
 	/* return our new hash value */
 	return hval;
 }
 
 /** Hash the string and output the encoded hash.
  * This uses modified RFC1924 Ascii85 encoding to accommodate systems with
  * very short name limits. We don't care about the encoding being reversible,
  * we just want to preserve as many bits of the input as possible in a
  * small printable string.
  * @param[in] str string to hash
  * @param[out] encbuf an array of 11 chars to hold the hash
  */
 static const char mdb_a85[]= "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
 
 static void ESECT
 mdb_pack85(unsigned long l, char *out)
 {
 	int i;
 
 	for (i=0; i<5; i++) {
 		*out++ = mdb_a85[l % 85];
 		l /= 85;
 	}
 }
 
 static void ESECT
 mdb_hash_enc(MDB_val *val, char *encbuf)
 {
 	mdb_hash_t h = mdb_hash_val(val, MDB_HASH_INIT);
 
 	mdb_pack85(h, encbuf);
 	mdb_pack85(h>>32, encbuf+5);
 	encbuf[10] = '\0';
 }
 #endif
 
 /** Open and/or initialize the lock region for the environment.
  * @param[in] env The LMDB environment.
  * @param[in] fname Filename + scratch area, from #mdb_fname_init().
  * @param[in] mode The Unix permissions for the file, if we create it.
  * @param[in,out] excl In -1, out lock type: -1 none, 0 shared, 1 exclusive
  * @return 0 on success, non-zero on failure.
  */
 static int ESECT
 mdb_env_setup_locks(MDB_env *env, MDB_name *fname, int mode, int *excl)
 {
 #ifdef _WIN32
 #	define MDB_ERRCODE_ROFS	ERROR_WRITE_PROTECT
 #else
 #	define MDB_ERRCODE_ROFS	EROFS
 #endif
 	int rc;
 	off_t size, rsize;
 
 	rc = mdb_fopen(env, fname, MDB_O_LOCKS, mode, &env->me_lfd);
 	if (rc) {
 		/* Omit lockfile if read-only env on read-only filesystem */
 		if (rc == MDB_ERRCODE_ROFS && (env->me_flags & MDB_RDONLY)) {
 			return MDB_SUCCESS;
 		}
 		goto fail;
 	}
 
 	if (!(env->me_flags & MDB_NOTLS)) {
 		rc = pthread_key_create(&env->me_txkey, mdb_env_reader_dest);
 		if (rc)
 			goto fail;
 		env->me_flags |= MDB_ENV_TXKEY;
 #ifdef _WIN32
 		/* Windows TLS callbacks need help finding their TLS info. */
 		if (mdb_tls_nkeys >= MAX_TLS_KEYS) {
 			rc = MDB_TLS_FULL;
 			goto fail;
 		}
 		mdb_tls_keys[mdb_tls_nkeys++] = env->me_txkey;
 #endif
 	}
 
 	/* Try to get exclusive lock. If we succeed, then
 	 * nobody is using the lock region and we should initialize it.
 	 */
 	if ((rc = mdb_env_excl_lock(env, excl))) goto fail;
 
 #ifdef _WIN32
 	size = GetFileSize(env->me_lfd, NULL);
 #else
 	size = lseek(env->me_lfd, 0, SEEK_END);
 	if (size == -1) goto fail_errno;
 #endif
 	rsize = (env->me_maxreaders-1) * sizeof(MDB_reader) + sizeof(MDB_txninfo);
 	if (size < rsize && *excl > 0) {
 #ifdef _WIN32
 		if (SetFilePointer(env->me_lfd, rsize, NULL, FILE_BEGIN) != (DWORD)rsize
 			|| !SetEndOfFile(env->me_lfd))
 			goto fail_errno;
 #else
 		if (ftruncate(env->me_lfd, rsize) != 0) goto fail_errno;
 #endif
 	} else {
 		rsize = size;
 		size = rsize - sizeof(MDB_txninfo);
 		env->me_maxreaders = size/sizeof(MDB_reader) + 1;
 	}
 	{
 #ifdef _WIN32
 		HANDLE mh;
 		mh = CreateFileMapping(env->me_lfd, NULL, PAGE_READWRITE,
 			0, 0, NULL);
 		if (!mh) goto fail_errno;
 		env->me_txns = MapViewOfFileEx(mh, FILE_MAP_WRITE, 0, 0, rsize, NULL);
 		CloseHandle(mh);
 		if (!env->me_txns) goto fail_errno;
 #else
 		void *m = mmap(NULL, rsize, PROT_READ|PROT_WRITE, MAP_SHARED,
 			env->me_lfd, 0);
 		if (m == MAP_FAILED) goto fail_errno;
 		env->me_txns = m;
 #endif
 	}
 	if (*excl > 0) {
 #ifdef _WIN32
 		BY_HANDLE_FILE_INFORMATION stbuf;
 		struct {
 			DWORD volume;
 			DWORD nhigh;
 			DWORD nlow;
 		} idbuf;
 		MDB_val val;
 		char encbuf[11];
 
 		if (!mdb_sec_inited) {
 			InitializeSecurityDescriptor(&mdb_null_sd,
 				SECURITY_DESCRIPTOR_REVISION);
 			SetSecurityDescriptorDacl(&mdb_null_sd, TRUE, 0, FALSE);
 			mdb_all_sa.nLength = sizeof(SECURITY_ATTRIBUTES);
 			mdb_all_sa.bInheritHandle = FALSE;
 			mdb_all_sa.lpSecurityDescriptor = &mdb_null_sd;
 			mdb_sec_inited = 1;
 		}
 		if (!GetFileInformationByHandle(env->me_lfd, &stbuf)) goto fail_errno;
 		idbuf.volume = stbuf.dwVolumeSerialNumber;
 		idbuf.nhigh  = stbuf.nFileIndexHigh;
 		idbuf.nlow   = stbuf.nFileIndexLow;
 		val.mv_data = &idbuf;
 		val.mv_size = sizeof(idbuf);
 		mdb_hash_enc(&val, encbuf);
 		sprintf(env->me_txns->mti_rmname, "Global\\MDBr%s", encbuf);
 		sprintf(env->me_txns->mti_wmname, "Global\\MDBw%s", encbuf);
 		env->me_rmutex = CreateMutexA(&mdb_all_sa, FALSE, env->me_txns->mti_rmname);
 		if (!env->me_rmutex) goto fail_errno;
 		env->me_wmutex = CreateMutexA(&mdb_all_sa, FALSE, env->me_txns->mti_wmname);
 		if (!env->me_wmutex) goto fail_errno;
 #elif defined(MDB_USE_POSIX_SEM)
 		struct stat stbuf;
 		struct {
 			dev_t dev;
 			ino_t ino;
 		} idbuf;
 		MDB_val val;
 		char encbuf[11];
 
 #if defined(__NetBSD__)
 #define	MDB_SHORT_SEMNAMES	1	/* limited to 14 chars */
 #endif
 		if (fstat(env->me_lfd, &stbuf)) goto fail_errno;
 		idbuf.dev = stbuf.st_dev;
 		idbuf.ino = stbuf.st_ino;
 		val.mv_data = &idbuf;
 		val.mv_size = sizeof(idbuf);
 		mdb_hash_enc(&val, encbuf);
 #ifdef MDB_SHORT_SEMNAMES
 		encbuf[9] = '\0';	/* drop name from 15 chars to 14 chars */
 #endif
 		sprintf(env->me_txns->mti_rmname, "/MDBr%s", encbuf);
 		sprintf(env->me_txns->mti_wmname, "/MDBw%s", encbuf);
 		/* Clean up after a previous run, if needed:  Try to
 		 * remove both semaphores before doing anything else.
 		 */
 		sem_unlink(env->me_txns->mti_rmname);
 		sem_unlink(env->me_txns->mti_wmname);
 		env->me_rmutex = sem_open(env->me_txns->mti_rmname,
 			O_CREAT|O_EXCL, mode, 1);
 		if (env->me_rmutex == SEM_FAILED) goto fail_errno;
 		env->me_wmutex = sem_open(env->me_txns->mti_wmname,
 			O_CREAT|O_EXCL, mode, 1);
 		if (env->me_wmutex == SEM_FAILED) goto fail_errno;
 #else	/* MDB_USE_POSIX_MUTEX: */
 		pthread_mutexattr_t mattr;
 
 		/* Solaris needs this before initing a robust mutex.  Otherwise
 		 * it may skip the init and return EBUSY "seems someone already
 		 * inited" or EINVAL "it was inited differently".
 		 */
 		memset(env->me_txns->mti_rmutex, 0, sizeof(*env->me_txns->mti_rmutex));
 		memset(env->me_txns->mti_wmutex, 0, sizeof(*env->me_txns->mti_wmutex));
 
 		if ((rc = pthread_mutexattr_init(&mattr)))
 			goto fail;
 
 		rc = pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
 #ifdef MDB_ROBUST_SUPPORTED
 		if (!rc) rc = pthread_mutexattr_setrobust(&mattr, PTHREAD_MUTEX_ROBUST);
 #endif
 		if (!rc) rc = pthread_mutex_init(env->me_txns->mti_rmutex, &mattr);
 		if (!rc) rc = pthread_mutex_init(env->me_txns->mti_wmutex, &mattr);
 		pthread_mutexattr_destroy(&mattr);
 		if (rc)
 			goto fail;
 #endif	/* _WIN32 || MDB_USE_POSIX_SEM */
 
 		env->me_txns->mti_magic = MDB_MAGIC;
 		env->me_txns->mti_format = MDB_LOCK_FORMAT;
 		env->me_txns->mti_txnid = 0;
 		env->me_txns->mti_numreaders = 0;
 
 	} else {
 		if (env->me_txns->mti_magic != MDB_MAGIC) {
 			DPUTS("lock region has invalid magic");
 			rc = MDB_INVALID;
 			goto fail;
 		}
 		if (env->me_txns->mti_format != MDB_LOCK_FORMAT) {
 			DPRINTF(("lock region has format+version 0x%x, expected 0x%x",
 				env->me_txns->mti_format, MDB_LOCK_FORMAT));
 			rc = MDB_VERSION_MISMATCH;
 			goto fail;
 		}
 		rc = ErrCode();
 		if (rc && rc != EACCES && rc != EAGAIN) {
 			goto fail;
 		}
 #ifdef _WIN32
 		env->me_rmutex = OpenMutexA(SYNCHRONIZE, FALSE, env->me_txns->mti_rmname);
 		if (!env->me_rmutex) goto fail_errno;
 		env->me_wmutex = OpenMutexA(SYNCHRONIZE, FALSE, env->me_txns->mti_wmname);
 		if (!env->me_wmutex) goto fail_errno;
 #elif defined(MDB_USE_POSIX_SEM)
 		env->me_rmutex = sem_open(env->me_txns->mti_rmname, 0);
 		if (env->me_rmutex == SEM_FAILED) goto fail_errno;
 		env->me_wmutex = sem_open(env->me_txns->mti_wmname, 0);
 		if (env->me_wmutex == SEM_FAILED) goto fail_errno;
 #endif
 	}
 	return MDB_SUCCESS;
 
 fail_errno:
 	rc = ErrCode();
 fail:
 	return rc;
 }
 
 	/** Only a subset of the @ref mdb_env flags can be changed
 	 *	at runtime. Changing other flags requires closing the
 	 *	environment and re-opening it with the new flags.
 	 */
 #define	CHANGEABLE	(MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
 #define	CHANGELESS	(MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY| \
 	MDB_WRITEMAP|MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
 
 #if VALID_FLAGS & PERSISTENT_FLAGS & (CHANGEABLE|CHANGELESS)
 # error "Persistent DB flags & env flags overlap, but both go in mm_flags"
 #endif
 
 int ESECT
 mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode)
 {
 	int rc, excl = -1;
 	MDB_name fname;
 
 	if (env->me_fd!=INVALID_HANDLE_VALUE || (flags & ~(CHANGEABLE|CHANGELESS)))
 		return EINVAL;
 
 	flags |= env->me_flags;
 
 	rc = mdb_fname_init(path, flags, &fname);
 	if (rc)
 		return rc;
 
 	if (flags & MDB_RDONLY) {
 		/* silently ignore WRITEMAP when we're only getting read access */
 		flags &= ~MDB_WRITEMAP;
 	} else {
 		if (!((env->me_free_pgs = mdb_midl_alloc(MDB_IDL_UM_MAX)) &&
 			  (env->me_dirty_list = calloc(MDB_IDL_UM_SIZE, sizeof(MDB_ID2)))))
 			rc = ENOMEM;
 	}
 	env->me_flags = flags |= MDB_ENV_ACTIVE;
 	if (rc)
 		goto leave;
 
 	env->me_path = strdup(path);
 	env->me_dbxs = calloc(env->me_maxdbs, sizeof(MDB_dbx));
 	env->me_dbflags = calloc(env->me_maxdbs, sizeof(uint16_t));
 	env->me_dbiseqs = calloc(env->me_maxdbs, sizeof(unsigned int));
 	if (!(env->me_dbxs && env->me_path && env->me_dbflags && env->me_dbiseqs)) {
 		rc = ENOMEM;
 		goto leave;
 	}
 	env->me_dbxs[FREE_DBI].md_cmp = mdb_cmp_long; /* aligned MDB_INTEGERKEY */
 
 	/* For RDONLY, get lockfile after we know datafile exists */
 	if (!(flags & (MDB_RDONLY|MDB_NOLOCK))) {
 		rc = mdb_env_setup_locks(env, &fname, mode, &excl);
 		if (rc)
 			goto leave;
 	}
 
 	rc = mdb_fopen(env, &fname,
 		(flags & MDB_RDONLY) ? MDB_O_RDONLY : MDB_O_RDWR,
 		mode, &env->me_fd);
 	if (rc)
 		goto leave;
 
 	if ((flags & (MDB_RDONLY|MDB_NOLOCK)) == MDB_RDONLY) {
 		rc = mdb_env_setup_locks(env, &fname, mode, &excl);
 		if (rc)
 			goto leave;
 	}
 
 	if ((rc = mdb_env_open2(env)) == MDB_SUCCESS) {
 		if (!(flags & (MDB_RDONLY|MDB_WRITEMAP))) {
 			/* Synchronous fd for meta writes. Needed even with
 			 * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
 			 */
 			rc = mdb_fopen(env, &fname, MDB_O_META, mode, &env->me_mfd);
 			if (rc)
 				goto leave;
 		}
 		DPRINTF(("opened dbenv %p", (void *) env));
 		if (excl > 0) {
 			rc = mdb_env_share_locks(env, &excl);
 			if (rc)
 				goto leave;
 		}
 		if (!(flags & MDB_RDONLY)) {
 			MDB_txn *txn;
 			int tsize = sizeof(MDB_txn), size = tsize + env->me_maxdbs *
 				(sizeof(MDB_db)+sizeof(MDB_cursor *)+sizeof(unsigned int)+1);
 			if ((env->me_pbuf = calloc(1, env->me_psize)) &&
 				(txn = calloc(1, size)))
 			{
 				txn->mt_dbs = (MDB_db *)((char *)txn + tsize);
 				txn->mt_cursors = (MDB_cursor **)(txn->mt_dbs + env->me_maxdbs);
 				txn->mt_dbiseqs = (unsigned int *)(txn->mt_cursors + env->me_maxdbs);
 				txn->mt_dbflags = (unsigned char *)(txn->mt_dbiseqs + env->me_maxdbs);
 				txn->mt_env = env;
 				txn->mt_dbxs = env->me_dbxs;
 				txn->mt_flags = MDB_TXN_FINISHED;
 				env->me_txn0 = txn;
 			} else {
 				rc = ENOMEM;
 			}
 		}
 	}
 
 leave:
 	if (rc) {
 		mdb_env_close0(env, excl);
 	}
 	mdb_fname_destroy(fname);
 	return rc;
 }
 
 /** Destroy resources from mdb_env_open(), clear our readers & DBIs */
 static void ESECT
 mdb_env_close0(MDB_env *env, int excl)
 {
 	int i;
 
 	if (!(env->me_flags & MDB_ENV_ACTIVE))
 		return;
 
 	/* Doing this here since me_dbxs may not exist during mdb_env_close */
 	if (env->me_dbxs) {
 		for (i = env->me_maxdbs; --i >= CORE_DBS; )
 			free(env->me_dbxs[i].md_name.mv_data);
 		free(env->me_dbxs);
 	}
 
 	free(env->me_pbuf);
 	free(env->me_dbiseqs);
 	free(env->me_dbflags);
 	free(env->me_path);
 	free(env->me_dirty_list);
 	free(env->me_txn0);
 	mdb_midl_free(env->me_free_pgs);
 
 	if (env->me_flags & MDB_ENV_TXKEY) {
 		pthread_key_delete(env->me_txkey);
 #ifdef _WIN32
 		/* Delete our key from the global list */
 		for (i=0; i<mdb_tls_nkeys; i++)
 			if (mdb_tls_keys[i] == env->me_txkey) {
 				mdb_tls_keys[i] = mdb_tls_keys[mdb_tls_nkeys-1];
 				mdb_tls_nkeys--;
 				break;
 			}
 #endif
 	}
 
 	if (env->me_map) {
 		munmap(env->me_map, env->me_mapsize);
 	}
 	if (env->me_mfd != INVALID_HANDLE_VALUE)
 		(void) close(env->me_mfd);
 	if (env->me_fd != INVALID_HANDLE_VALUE)
 		(void) close(env->me_fd);
 	if (env->me_txns) {
 		MDB_PID_T pid = getpid();
 		/* Clearing readers is done in this function because
 		 * me_txkey with its destructor must be disabled first.
 		 *
 		 * We skip the the reader mutex, so we touch only
 		 * data owned by this process (me_close_readers and
 		 * our readers), and clear each reader atomically.
 		 */
 		for (i = env->me_close_readers; --i >= 0; )
 			if (env->me_txns->mti_readers[i].mr_pid == pid)
 				env->me_txns->mti_readers[i].mr_pid = 0;
 #ifdef _WIN32
 		if (env->me_rmutex) {
 			CloseHandle(env->me_rmutex);
 			if (env->me_wmutex) CloseHandle(env->me_wmutex);
 		}
 		/* Windows automatically destroys the mutexes when
 		 * the last handle closes.
 		 */
 #elif defined(MDB_USE_POSIX_SEM)
 		if (env->me_rmutex != SEM_FAILED) {
 			sem_close(env->me_rmutex);
 			if (env->me_wmutex != SEM_FAILED)
 				sem_close(env->me_wmutex);
 			/* If we have the filelock:  If we are the
 			 * only remaining user, clean up semaphores.
 			 */
 			if (excl == 0)
 				mdb_env_excl_lock(env, &excl);
 			if (excl > 0) {
 				sem_unlink(env->me_txns->mti_rmname);
 				sem_unlink(env->me_txns->mti_wmname);
 			}
 		}
 #elif defined(MDB_ROBUST_SUPPORTED)
 		/* If we have the filelock:  If we are the
 		 * only remaining user, clean up robust
 		 * mutexes.
 		 */
 		if (excl == 0)
 			mdb_env_excl_lock(env, &excl);
 		if (excl > 0) {
 			pthread_mutex_destroy(env->me_txns->mti_rmutex);
 			pthread_mutex_destroy(env->me_txns->mti_wmutex);
 		}
 #endif
 		munmap((void *)env->me_txns, (env->me_maxreaders-1)*sizeof(MDB_reader)+sizeof(MDB_txninfo));
 	}
 	if (env->me_lfd != INVALID_HANDLE_VALUE) {
 #ifdef _WIN32
 		if (excl >= 0) {
 			/* Unlock the lockfile.  Windows would have unlocked it
 			 * after closing anyway, but not necessarily at once.
 			 */
 			UnlockFile(env->me_lfd, 0, 0, 1, 0);
 		}
 #endif
 		(void) close(env->me_lfd);
 	}
 
 	env->me_flags &= ~(MDB_ENV_ACTIVE|MDB_ENV_TXKEY);
 }
 
 void ESECT
 mdb_env_close(MDB_env *env)
 {
 	MDB_page *dp;
 
 	if (env == NULL)
 		return;
 
 	VGMEMP_DESTROY(env);
 	while ((dp = env->me_dpages) != NULL) {
 		VGMEMP_DEFINED(&dp->mp_next, sizeof(dp->mp_next));
 		env->me_dpages = dp->mp_next;
 		free(dp);
 	}
 
 	mdb_env_close0(env, 0);
 	free(env);
 }
 
 /** Compare two items pointing at aligned size_t's */
 static int
 mdb_cmp_long(const MDB_val *a, const MDB_val *b)
 {
 	return (*(size_t *)a->mv_data < *(size_t *)b->mv_data) ? -1 :
 		*(size_t *)a->mv_data > *(size_t *)b->mv_data;
 }
 
 /** Compare two items pointing at aligned unsigned int's.
  *
  *	This is also set as #MDB_INTEGERDUP|#MDB_DUPFIXED's #MDB_dbx.%md_dcmp,
  *	but #mdb_cmp_clong() is called instead if the data type is size_t.
  */
 static int
 mdb_cmp_int(const MDB_val *a, const MDB_val *b)
 {
 	return (*(unsigned int *)a->mv_data < *(unsigned int *)b->mv_data) ? -1 :
 		*(unsigned int *)a->mv_data > *(unsigned int *)b->mv_data;
 }
 
 /** Compare two items pointing at unsigned ints of unknown alignment.
  *	Nodes and keys are guaranteed to be 2-byte aligned.
  */
 static int
 mdb_cmp_cint(const MDB_val *a, const MDB_val *b)
 {
 #if BYTE_ORDER == LITTLE_ENDIAN
 	unsigned short *u, *c;
 	int x;
 
 	u = (unsigned short *) ((char *) a->mv_data + a->mv_size);
 	c = (unsigned short *) ((char *) b->mv_data + a->mv_size);
 	do {
 		x = *--u - *--c;
 	} while(!x && u > (unsigned short *)a->mv_data);
 	return x;
 #else
 	unsigned short *u, *c, *end;
 	int x;
 
 	end = (unsigned short *) ((char *) a->mv_data + a->mv_size);
 	u = (unsigned short *)a->mv_data;
 	c = (unsigned short *)b->mv_data;
 	do {
 		x = *u++ - *c++;
 	} while(!x && u < end);
 	return x;
 #endif
 }
 
 /** Compare two items lexically */
 static int
 mdb_cmp_memn(const MDB_val *a, const MDB_val *b)
 {
 	int diff;
 	ssize_t len_diff;
 	unsigned int len;
 
 	len = a->mv_size;
 	len_diff = (ssize_t) a->mv_size - (ssize_t) b->mv_size;
 	if (len_diff > 0) {
 		len = b->mv_size;
 		len_diff = 1;
 	}
 
 	diff = memcmp(a->mv_data, b->mv_data, len);
 	return diff ? diff : len_diff<0 ? -1 : len_diff;
 }
 
 /** Compare two items in reverse byte order */
 static int
 mdb_cmp_memnr(const MDB_val *a, const MDB_val *b)
 {
 	const unsigned char	*p1, *p2, *p1_lim;
 	ssize_t len_diff;
 	int diff;
 
 	p1_lim = (const unsigned char *)a->mv_data;
 	p1 = (const unsigned char *)a->mv_data + a->mv_size;
 	p2 = (const unsigned char *)b->mv_data + b->mv_size;
 
 	len_diff = (ssize_t) a->mv_size - (ssize_t) b->mv_size;
 	if (len_diff > 0) {
 		p1_lim += len_diff;
 		len_diff = 1;
 	}
 
 	while (p1 > p1_lim) {
 		diff = *--p1 - *--p2;
 		if (diff)
 			return diff;
 	}
 	return len_diff<0 ? -1 : len_diff;
 }
 
 /** Search for key within a page, using binary search.
  * Returns the smallest entry larger or equal to the key.
  * If exactp is non-null, stores whether the found entry was an exact match
  * in *exactp (1 or 0).
  * Updates the cursor index with the index of the found entry.
  * If no entry larger or equal to the key is found, returns NULL.
  */
 static MDB_node *
 mdb_node_search(MDB_cursor *mc, MDB_val *key, int *exactp)
 {
 	unsigned int	 i = 0, nkeys;
 	int		 low, high;
 	int		 rc = 0;
 	MDB_page *mp = mc->mc_pg[mc->mc_top];
 	MDB_node	*node = NULL;
 	MDB_val	 nodekey;
 	MDB_cmp_func *cmp;
 	DKBUF;
 
 	nkeys = NUMKEYS(mp);
 
 	DPRINTF(("searching %u keys in %s %spage %"Z"u",
 	    nkeys, IS_LEAF(mp) ? "leaf" : "branch", IS_SUBP(mp) ? "sub-" : "",
 	    mdb_dbg_pgno(mp)));
 
 	low = IS_LEAF(mp) ? 0 : 1;
 	high = nkeys - 1;
 	cmp = mc->mc_dbx->md_cmp;
 
 	/* Branch pages have no data, so if using integer keys,
 	 * alignment is guaranteed. Use faster mdb_cmp_int.
 	 */
 	if (cmp == mdb_cmp_cint && IS_BRANCH(mp)) {
 		if (NODEPTR(mp, 1)->mn_ksize == sizeof(size_t))
 			cmp = mdb_cmp_long;
 		else
 			cmp = mdb_cmp_int;
 	}
 
 	if (IS_LEAF2(mp)) {
 		nodekey.mv_size = mc->mc_db->md_pad;
 		node = NODEPTR(mp, 0);	/* fake */
 		while (low <= high) {
 			i = (low + high) >> 1;
 			nodekey.mv_data = LEAF2KEY(mp, i, nodekey.mv_size);
 			rc = cmp(key, &nodekey);
 			DPRINTF(("found leaf index %u [%s], rc = %i",
 			    i, DKEY(&nodekey), rc));
 			if (rc == 0)
 				break;
 			if (rc > 0)
 				low = i + 1;
 			else
 				high = i - 1;
 		}
 	} else {
 		while (low <= high) {
 			i = (low + high) >> 1;
 
 			node = NODEPTR(mp, i);
 			nodekey.mv_size = NODEKSZ(node);
 			nodekey.mv_data = NODEKEY(node);
 
 			rc = cmp(key, &nodekey);
 #if MDB_DEBUG
 			if (IS_LEAF(mp))
 				DPRINTF(("found leaf index %u [%s], rc = %i",
 				    i, DKEY(&nodekey), rc));
 			else
 				DPRINTF(("found branch index %u [%s -> %"Z"u], rc = %i",
 				    i, DKEY(&nodekey), NODEPGNO(node), rc));
 #endif
 			if (rc == 0)
 				break;
 			if (rc > 0)
 				low = i + 1;
 			else
 				high = i - 1;
 		}
 	}
 
 	if (rc > 0) {	/* Found entry is less than the key. */
 		i++;	/* Skip to get the smallest entry larger than key. */
 		if (!IS_LEAF2(mp))
 			node = NODEPTR(mp, i);
 	}
 	if (exactp)
 		*exactp = (rc == 0 && nkeys > 0);
 	/* store the key index */
 	mc->mc_ki[mc->mc_top] = i;
 	if (i >= nkeys)
 		/* There is no entry larger or equal to the key. */
 		return NULL;
 
 	/* nodeptr is fake for LEAF2 */
 	return node;
 }
 
 #if 0
 static void
 mdb_cursor_adjust(MDB_cursor *mc, func)
 {
 	MDB_cursor *m2;
 
 	for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
 		if (m2->mc_pg[m2->mc_top] == mc->mc_pg[mc->mc_top]) {
 			func(mc, m2);
 		}
 	}
 }
 #endif
 
 /** Pop a page off the top of the cursor's stack. */
 static void
 mdb_cursor_pop(MDB_cursor *mc)
 {
 	if (mc->mc_snum) {
 		DPRINTF(("popping page %"Z"u off db %d cursor %p",
 			mc->mc_pg[mc->mc_top]->mp_pgno, DDBI(mc), (void *) mc));
 
 		mc->mc_snum--;
 		if (mc->mc_snum) {
 			mc->mc_top--;
 		} else {
 			mc->mc_flags &= ~C_INITIALIZED;
 		}
 	}
 }
 
 /** Push a page onto the top of the cursor's stack.
  * Set #MDB_TXN_ERROR on failure.
  */
 static int
 mdb_cursor_push(MDB_cursor *mc, MDB_page *mp)
 {
 	DPRINTF(("pushing page %"Z"u on db %d cursor %p", mp->mp_pgno,
 		DDBI(mc), (void *) mc));
 
 	if (mc->mc_snum >= CURSOR_STACK) {
 		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 		return MDB_CURSOR_FULL;
 	}
 
 	mc->mc_top = mc->mc_snum++;
 	mc->mc_pg[mc->mc_top] = mp;
 	mc->mc_ki[mc->mc_top] = 0;
 
 	return MDB_SUCCESS;
 }
 
 /** Find the address of the page corresponding to a given page number.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in] mc the cursor accessing the page.
  * @param[in] pgno the page number for the page to retrieve.
  * @param[out] ret address of a pointer where the page's address will be stored.
  * @param[out] lvl dirty_list inheritance level of found page. 1=current txn, 0=mapped page.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_get(MDB_cursor *mc, pgno_t pgno, MDB_page **ret, int *lvl)
 {
 	MDB_txn *txn = mc->mc_txn;
 	MDB_env *env = txn->mt_env;
 	MDB_page *p = NULL;
 	int level;
 
 	if (! (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_WRITEMAP))) {
 		MDB_txn *tx2 = txn;
 		level = 1;
 		do {
 			MDB_ID2L dl = tx2->mt_u.dirty_list;
 			unsigned x;
 			/* Spilled pages were dirtied in this txn and flushed
 			 * because the dirty list got full. Bring this page
 			 * back in from the map (but don't unspill it here,
 			 * leave that unless page_touch happens again).
 			 */
 			if (tx2->mt_spill_pgs) {
 				MDB_ID pn = pgno << 1;
 				x = mdb_midl_search(tx2->mt_spill_pgs, pn);
 				if (x <= tx2->mt_spill_pgs[0] && tx2->mt_spill_pgs[x] == pn) {
 					p = (MDB_page *)(env->me_map + env->me_psize * pgno);
 					goto done;
 				}
 			}
 			if (dl[0].mid) {
 				unsigned x = mdb_mid2l_search(dl, pgno);
 				if (x <= dl[0].mid && dl[x].mid == pgno) {
 					p = dl[x].mptr;
 					goto done;
 				}
 			}
 			level++;
 		} while ((tx2 = tx2->mt_parent) != NULL);
 	}
 
 	if (pgno < txn->mt_next_pgno) {
 		level = 0;
 		p = (MDB_page *)(env->me_map + env->me_psize * pgno);
 	} else {
 		DPRINTF(("page %"Z"u not found", pgno));
 		txn->mt_flags |= MDB_TXN_ERROR;
 		return MDB_PAGE_NOTFOUND;
 	}
 
 done:
 	*ret = p;
 	if (lvl)
 		*lvl = level;
 	return MDB_SUCCESS;
 }
 
 /** Finish #mdb_page_search() / #mdb_page_search_lowest().
  *	The cursor is at the root page, set up the rest of it.
  */
 static int
 mdb_page_search_root(MDB_cursor *mc, MDB_val *key, int flags)
 {
 	MDB_page	*mp = mc->mc_pg[mc->mc_top];
 	int rc;
 	DKBUF;
 
 	while (IS_BRANCH(mp)) {
 		MDB_node	*node;
 		indx_t		i;
 
 		DPRINTF(("branch page %"Z"u has %u keys", mp->mp_pgno, NUMKEYS(mp)));
 		/* Don't assert on branch pages in the FreeDB. We can get here
 		 * while in the process of rebalancing a FreeDB branch page; we must
 		 * let that proceed. ITS#8336
 		 */
 		mdb_cassert(mc, !mc->mc_dbi || NUMKEYS(mp) > 1);
 		DPRINTF(("found index 0 to page %"Z"u", NODEPGNO(NODEPTR(mp, 0))));
 
 		if (flags & (MDB_PS_FIRST|MDB_PS_LAST)) {
 			i = 0;
 			if (flags & MDB_PS_LAST) {
 				i = NUMKEYS(mp) - 1;
 				/* if already init'd, see if we're already in right place */
 				if (mc->mc_flags & C_INITIALIZED) {
 					if (mc->mc_ki[mc->mc_top] == i) {
 						mc->mc_top = mc->mc_snum++;
 						mp = mc->mc_pg[mc->mc_top];
 						goto ready;
 					}
 				}
 			}
 		} else {
 			int	 exact;
 			node = mdb_node_search(mc, key, &exact);
 			if (node == NULL)
 				i = NUMKEYS(mp) - 1;
 			else {
 				i = mc->mc_ki[mc->mc_top];
 				if (!exact) {
 					mdb_cassert(mc, i > 0);
 					i--;
 				}
 			}
 			DPRINTF(("following index %u for key [%s]", i, DKEY(key)));
 		}
 
 		mdb_cassert(mc, i < NUMKEYS(mp));
 		node = NODEPTR(mp, i);
 
 		if ((rc = mdb_page_get(mc, NODEPGNO(node), &mp, NULL)) != 0)
 			return rc;
 
 		mc->mc_ki[mc->mc_top] = i;
 		if ((rc = mdb_cursor_push(mc, mp)))
 			return rc;
 
 ready:
 		if (flags & MDB_PS_MODIFY) {
 			if ((rc = mdb_page_touch(mc)) != 0)
 				return rc;
 			mp = mc->mc_pg[mc->mc_top];
 		}
 	}
 
 	if (!IS_LEAF(mp)) {
 		DPRINTF(("internal error, index points to a %02X page!?",
 		    mp->mp_flags));
 		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 		return MDB_CORRUPTED;
 	}
 
 	DPRINTF(("found leaf page %"Z"u for key [%s]", mp->mp_pgno,
 	    key ? DKEY(key) : "null"));
 	mc->mc_flags |= C_INITIALIZED;
 	mc->mc_flags &= ~C_EOF;
 
 	return MDB_SUCCESS;
 }
 
 /** Search for the lowest key under the current branch page.
  * This just bypasses a NUMKEYS check in the current page
  * before calling mdb_page_search_root(), because the callers
  * are all in situations where the current page is known to
  * be underfilled.
  */
 static int
 mdb_page_search_lowest(MDB_cursor *mc)
 {
 	MDB_page	*mp = mc->mc_pg[mc->mc_top];
 	MDB_node	*node = NODEPTR(mp, 0);
 	int rc;
 
 	if ((rc = mdb_page_get(mc, NODEPGNO(node), &mp, NULL)) != 0)
 		return rc;
 
 	mc->mc_ki[mc->mc_top] = 0;
 	if ((rc = mdb_cursor_push(mc, mp)))
 		return rc;
 	return mdb_page_search_root(mc, NULL, MDB_PS_FIRST);
 }
 
 /** Search for the page a given key should be in.
  * Push it and its parent pages on the cursor stack.
  * @param[in,out] mc the cursor for this operation.
  * @param[in] key the key to search for, or NULL for first/last page.
  * @param[in] flags If MDB_PS_MODIFY is set, visited pages in the DB
  *   are touched (updated with new page numbers).
  *   If MDB_PS_FIRST or MDB_PS_LAST is set, find first or last leaf.
  *   This is used by #mdb_cursor_first() and #mdb_cursor_last().
  *   If MDB_PS_ROOTONLY set, just fetch root node, no further lookups.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_search(MDB_cursor *mc, MDB_val *key, int flags)
 {
 	int		 rc;
 	pgno_t		 root;
 
 	/* Make sure the txn is still viable, then find the root from
 	 * the txn's db table and set it as the root of the cursor's stack.
 	 */
 	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED) {
 		DPUTS("transaction may not be used now");
 		return MDB_BAD_TXN;
 	} else {
 		/* Make sure we're using an up-to-date root */
 		if (*mc->mc_dbflag & DB_STALE) {
 				MDB_cursor mc2;
 				if (TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi))
 					return MDB_BAD_DBI;
 				mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, NULL);
 				rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, 0);
 				if (rc)
 					return rc;
 				{
 					MDB_val data;
 					int exact = 0;
 					uint16_t flags;
 					MDB_node *leaf = mdb_node_search(&mc2,
 						&mc->mc_dbx->md_name, &exact);
 					if (!exact)
 						return MDB_NOTFOUND;
 					if ((leaf->mn_flags & (F_DUPDATA|F_SUBDATA)) != F_SUBDATA)
 						return MDB_INCOMPATIBLE; /* not a named DB */
 					rc = mdb_node_read(&mc2, leaf, &data);
 					if (rc)
 						return rc;
 					memcpy(&flags, ((char *) data.mv_data + offsetof(MDB_db, md_flags)),
 						sizeof(uint16_t));
 					/* The txn may not know this DBI, or another process may
 					 * have dropped and recreated the DB with other flags.
 					 */
 					if ((mc->mc_db->md_flags & PERSISTENT_FLAGS) != flags)
 						return MDB_INCOMPATIBLE;
 					memcpy(mc->mc_db, data.mv_data, sizeof(MDB_db));
 				}
 				*mc->mc_dbflag &= ~DB_STALE;
 		}
 		root = mc->mc_db->md_root;
 
 		if (root == P_INVALID) {		/* Tree is empty. */
 			DPUTS("tree is empty");
 			return MDB_NOTFOUND;
 		}
 	}
 
 	mdb_cassert(mc, root > 1);
 	if (!mc->mc_pg[0] || mc->mc_pg[0]->mp_pgno != root)
 		if ((rc = mdb_page_get(mc, root, &mc->mc_pg[0], NULL)) != 0)
 			return rc;
 
 	mc->mc_snum = 1;
 	mc->mc_top = 0;
 
 	DPRINTF(("db %d root page %"Z"u has flags 0x%X",
 		DDBI(mc), root, mc->mc_pg[0]->mp_flags));
 
 	if (flags & MDB_PS_MODIFY) {
 		if ((rc = mdb_page_touch(mc)))
 			return rc;
 	}
 
 	if (flags & MDB_PS_ROOTONLY)
 		return MDB_SUCCESS;
 
 	return mdb_page_search_root(mc, key, flags);
 }
 
 static int
 mdb_ovpage_free(MDB_cursor *mc, MDB_page *mp)
 {
 	MDB_txn *txn = mc->mc_txn;
 	pgno_t pg = mp->mp_pgno;
 	unsigned x = 0, ovpages = mp->mp_pages;
 	MDB_env *env = txn->mt_env;
 	MDB_IDL sl = txn->mt_spill_pgs;
 	MDB_ID pn = pg << 1;
 	int rc;
 
 	DPRINTF(("free ov page %"Z"u (%d)", pg, ovpages));
 	/* If the page is dirty or on the spill list we just acquired it,
 	 * so we should give it back to our current free list, if any.
 	 * Otherwise put it onto the list of pages we freed in this txn.
 	 *
 	 * Won't create me_pghead: me_pglast must be inited along with it.
 	 * Unsupported in nested txns: They would need to hide the page
 	 * range in ancestor txns' dirty and spilled lists.
 	 */
 	if (env->me_pghead &&
 		!txn->mt_parent &&
 		((mp->mp_flags & P_DIRTY) ||
 		 (sl && (x = mdb_midl_search(sl, pn)) <= sl[0] && sl[x] == pn)))
 	{
 		unsigned i, j;
 		pgno_t *mop;
 		MDB_ID2 *dl, ix, iy;
 		rc = mdb_midl_need(&env->me_pghead, ovpages);
 		if (rc)
 			return rc;
 		if (!(mp->mp_flags & P_DIRTY)) {
 			/* This page is no longer spilled */
 			if (x == sl[0])
 				sl[0]--;
 			else
 				sl[x] |= 1;
 			goto release;
 		}
 		/* Remove from dirty list */
 		dl = txn->mt_u.dirty_list;
 		x = dl[0].mid--;
 		for (ix = dl[x]; ix.mptr != mp; ix = iy) {
 			if (x > 1) {
 				x--;
 				iy = dl[x];
 				dl[x] = ix;
 			} else {
 				mdb_cassert(mc, x > 1);
 				j = ++(dl[0].mid);
 				dl[j] = ix;		/* Unsorted. OK when MDB_TXN_ERROR. */
 				txn->mt_flags |= MDB_TXN_ERROR;
 				return MDB_CORRUPTED;
 			}
 		}
 		txn->mt_dirty_room++;
 		if (!(env->me_flags & MDB_WRITEMAP))
 			mdb_dpage_free(env, mp);
 release:
 		/* Insert in me_pghead */
 		mop = env->me_pghead;
 		j = mop[0] + ovpages;
 		for (i = mop[0]; i && mop[i] < pg; i--)
 			mop[j--] = mop[i];
 		while (j>i)
 			mop[j--] = pg++;
 		mop[0] += ovpages;
 	} else {
 		rc = mdb_midl_append_range(&txn->mt_free_pgs, pg, ovpages);
 		if (rc)
 			return rc;
 	}
 	mc->mc_db->md_overflow_pages -= ovpages;
 	return 0;
 }
 
 /** Return the data associated with a given node.
  * @param[in] mc The cursor for this operation.
  * @param[in] leaf The node being read.
  * @param[out] data Updated to point to the node's data.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_node_read(MDB_cursor *mc, MDB_node *leaf, MDB_val *data)
 {
 	MDB_page	*omp;		/* overflow page */
 	pgno_t		 pgno;
 	int rc;
 
 	if (!F_ISSET(leaf->mn_flags, F_BIGDATA)) {
 		data->mv_size = NODEDSZ(leaf);
 		data->mv_data = NODEDATA(leaf);
 		return MDB_SUCCESS;
 	}
 
 	/* Read overflow data.
 	 */
 	data->mv_size = NODEDSZ(leaf);
 	memcpy(&pgno, NODEDATA(leaf), sizeof(pgno));
 	if ((rc = mdb_page_get(mc, pgno, &omp, NULL)) != 0) {
 		DPRINTF(("read overflow page %"Z"u failed", pgno));
 		return rc;
 	}
 	data->mv_data = METADATA(omp);
 
 	return MDB_SUCCESS;
 }
 
 int
 mdb_get(MDB_txn *txn, MDB_dbi dbi,
     MDB_val *key, MDB_val *data)
 {
 	MDB_cursor	mc;
 	MDB_xcursor	mx;
 	int exact = 0;
 	DKBUF;
 
 	DPRINTF(("===> get db %u key [%s]", dbi, DKEY(key)));
 
 	if (!key || !data || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	if (txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	mdb_cursor_init(&mc, txn, dbi, &mx);
 	return mdb_cursor_set(&mc, key, data, MDB_SET, &exact);
 }
 
 /** Find a sibling for a page.
  * Replaces the page at the top of the cursor's stack with the
  * specified sibling, if one exists.
  * @param[in] mc The cursor for this operation.
  * @param[in] move_right Non-zero if the right sibling is requested,
  * otherwise the left sibling.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_cursor_sibling(MDB_cursor *mc, int move_right)
 {
 	int		 rc;
 	MDB_node	*indx;
 	MDB_page	*mp;
 
 	if (mc->mc_snum < 2) {
 		return MDB_NOTFOUND;		/* root has no siblings */
 	}
 
 	mdb_cursor_pop(mc);
 	DPRINTF(("parent page is page %"Z"u, index %u",
 		mc->mc_pg[mc->mc_top]->mp_pgno, mc->mc_ki[mc->mc_top]));
 
 	if (move_right ? (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mc->mc_pg[mc->mc_top]))
 		       : (mc->mc_ki[mc->mc_top] == 0)) {
 		DPRINTF(("no more keys left, moving to %s sibling",
 		    move_right ? "right" : "left"));
 		if ((rc = mdb_cursor_sibling(mc, move_right)) != MDB_SUCCESS) {
 			/* undo cursor_pop before returning */
 			mc->mc_top++;
 			mc->mc_snum++;
 			return rc;
 		}
 	} else {
 		if (move_right)
 			mc->mc_ki[mc->mc_top]++;
 		else
 			mc->mc_ki[mc->mc_top]--;
 		DPRINTF(("just moving to %s index key %u",
 		    move_right ? "right" : "left", mc->mc_ki[mc->mc_top]));
 	}
 	mdb_cassert(mc, IS_BRANCH(mc->mc_pg[mc->mc_top]));
 
 	indx = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 	if ((rc = mdb_page_get(mc, NODEPGNO(indx), &mp, NULL)) != 0) {
 		/* mc will be inconsistent if caller does mc_snum++ as above */
 		mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
 		return rc;
 	}
 
 	mdb_cursor_push(mc, mp);
 	if (!move_right)
 		mc->mc_ki[mc->mc_top] = NUMKEYS(mp)-1;
 
 	return MDB_SUCCESS;
 }
 
 /** Move the cursor to the next data item. */
 static int
 mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
 {
 	MDB_page	*mp;
 	MDB_node	*leaf;
 	int rc;
 
 	if ((mc->mc_flags & C_DEL && op == MDB_NEXT_DUP))
 		return MDB_NOTFOUND;
 
 	if (!(mc->mc_flags & C_INITIALIZED))
 		return mdb_cursor_first(mc, key, data);
 
 	mp = mc->mc_pg[mc->mc_top];
 
 	if (mc->mc_flags & C_EOF) {
 		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mp)-1)
 			return MDB_NOTFOUND;
 		mc->mc_flags ^= C_EOF;
 	}
 
 	if (mc->mc_db->md_flags & MDB_DUPSORT) {
 		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 			if (op == MDB_NEXT || op == MDB_NEXT_DUP) {
 				rc = mdb_cursor_next(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_NEXT);
 				if (op != MDB_NEXT || rc != MDB_NOTFOUND) {
 					if (rc == MDB_SUCCESS)
 						MDB_GET_KEY(leaf, key);
 					return rc;
 				}
 			}
 		} else {
 			mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 			if (op == MDB_NEXT_DUP)
 				return MDB_NOTFOUND;
 		}
 	}
 
 	DPRINTF(("cursor_next: top page is %"Z"u in cursor %p",
 		mdb_dbg_pgno(mp), (void *) mc));
 	if (mc->mc_flags & C_DEL) {
 		mc->mc_flags ^= C_DEL;
 		goto skip;
 	}
 
 	if (mc->mc_ki[mc->mc_top] + 1u >= NUMKEYS(mp)) {
 		DPUTS("=====> move to next sibling page");
 		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS) {
 			mc->mc_flags |= C_EOF;
 			return rc;
 		}
 		mp = mc->mc_pg[mc->mc_top];
 		DPRINTF(("next page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
 	} else
 		mc->mc_ki[mc->mc_top]++;
 
 skip:
 	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
 	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
 
 	if (IS_LEAF2(mp)) {
 		key->mv_size = mc->mc_db->md_pad;
 		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
 		return MDB_SUCCESS;
 	}
 
 	mdb_cassert(mc, IS_LEAF(mp));
 	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
 		rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
 		if (rc != MDB_SUCCESS)
 			return rc;
 	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
 	}
 
 	MDB_GET_KEY(leaf, key);
 	return MDB_SUCCESS;
 }
 
 /** Move the cursor to the previous data item. */
 static int
 mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
 {
 	MDB_page	*mp;
 	MDB_node	*leaf;
 	int rc;
 
 	if (!(mc->mc_flags & C_INITIALIZED)) {
 		rc = mdb_cursor_last(mc, key, data);
 		if (rc)
 			return rc;
 		mc->mc_ki[mc->mc_top]++;
 	}
 
 	mp = mc->mc_pg[mc->mc_top];
 
 	if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
 		mc->mc_ki[mc->mc_top] < NUMKEYS(mp)) {
 		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 			if (op == MDB_PREV || op == MDB_PREV_DUP) {
 				rc = mdb_cursor_prev(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_PREV);
 				if (op != MDB_PREV || rc != MDB_NOTFOUND) {
 					if (rc == MDB_SUCCESS) {
 						MDB_GET_KEY(leaf, key);
 						mc->mc_flags &= ~C_EOF;
 					}
 					return rc;
 				}
 			}
 		} else {
 			mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 			if (op == MDB_PREV_DUP)
 				return MDB_NOTFOUND;
 		}
 	}
 
 	DPRINTF(("cursor_prev: top page is %"Z"u in cursor %p",
 		mdb_dbg_pgno(mp), (void *) mc));
 
 	mc->mc_flags &= ~(C_EOF|C_DEL);
 
 	if (mc->mc_ki[mc->mc_top] == 0)  {
 		DPUTS("=====> move to prev sibling page");
 		if ((rc = mdb_cursor_sibling(mc, 0)) != MDB_SUCCESS) {
 			return rc;
 		}
 		mp = mc->mc_pg[mc->mc_top];
 		mc->mc_ki[mc->mc_top] = NUMKEYS(mp) - 1;
 		DPRINTF(("prev page is %"Z"u, key index %u", mp->mp_pgno, mc->mc_ki[mc->mc_top]));
 	} else
 		mc->mc_ki[mc->mc_top]--;
 
 	DPRINTF(("==> cursor points to page %"Z"u with %u keys, key index %u",
 	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
 
 	if (!IS_LEAF(mp))
 		return MDB_CORRUPTED;
 
 	if (IS_LEAF2(mp)) {
 		key->mv_size = mc->mc_db->md_pad;
 		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
 		return MDB_SUCCESS;
 	}
 
 	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
 		rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
 		if (rc != MDB_SUCCESS)
 			return rc;
 	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
 	}
 
 	MDB_GET_KEY(leaf, key);
 	return MDB_SUCCESS;
 }
 
 /** Set the cursor on a specific data item. */
 static int
 mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data,
     MDB_cursor_op op, int *exactp)
 {
 	int		 rc;
 	MDB_page	*mp;
 	MDB_node	*leaf = NULL;
 	DKBUF;
 
 	if (key->mv_size == 0)
 		return MDB_BAD_VALSIZE;
 
 	if (mc->mc_xcursor)
 		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 
 	/* See if we're already on the right page */
 	if (mc->mc_flags & C_INITIALIZED) {
 		MDB_val nodekey;
 
 		mp = mc->mc_pg[mc->mc_top];
 		if (!NUMKEYS(mp)) {
 			mc->mc_ki[mc->mc_top] = 0;
 			return MDB_NOTFOUND;
 		}
 		if (MP_FLAGS(mp) & P_LEAF2) {
 			nodekey.mv_size = mc->mc_db->md_pad;
 			nodekey.mv_data = LEAF2KEY(mp, 0, nodekey.mv_size);
 		} else {
 			leaf = NODEPTR(mp, 0);
 			MDB_GET_KEY2(leaf, nodekey);
 		}
 		rc = mc->mc_dbx->md_cmp(key, &nodekey);
 		if (rc == 0) {
 			/* Probably happens rarely, but first node on the page
 			 * was the one we wanted.
 			 */
 			mc->mc_ki[mc->mc_top] = 0;
 			if (exactp)
 				*exactp = 1;
 			goto set1;
 		}
 		if (rc > 0) {
 			unsigned int i;
 			unsigned int nkeys = NUMKEYS(mp);
 			if (nkeys > 1) {
 				if (MP_FLAGS(mp) & P_LEAF2) {
 					nodekey.mv_data = LEAF2KEY(mp,
 						 nkeys-1, nodekey.mv_size);
 				} else {
 					leaf = NODEPTR(mp, nkeys-1);
 					MDB_GET_KEY2(leaf, nodekey);
 				}
 				rc = mc->mc_dbx->md_cmp(key, &nodekey);
 				if (rc == 0) {
 					/* last node was the one we wanted */
 					mc->mc_ki[mc->mc_top] = nkeys-1;
 					if (exactp)
 						*exactp = 1;
 					goto set1;
 				}
 				if (rc < 0) {
 					if (mc->mc_ki[mc->mc_top] < NUMKEYS(mp)) {
 						/* This is definitely the right page, skip search_page */
 						if (MP_FLAGS(mp) & P_LEAF2) {
 							nodekey.mv_data = LEAF2KEY(mp,
 								 mc->mc_ki[mc->mc_top], nodekey.mv_size);
 						} else {
 							leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 							MDB_GET_KEY2(leaf, nodekey);
 						}
 						rc = mc->mc_dbx->md_cmp(key, &nodekey);
 						if (rc == 0) {
 							/* current node was the one we wanted */
 							if (exactp)
 								*exactp = 1;
 							goto set1;
 						}
 					}
 					rc = 0;
 					mc->mc_flags &= ~C_EOF;
 					goto set2;
 				}
 			}
 			/* If any parents have right-sibs, search.
 			 * Otherwise, there's nothing further.
 			 */
 			for (i=0; i<mc->mc_top; i++)
 				if (mc->mc_ki[i] <
 					NUMKEYS(mc->mc_pg[i])-1)
 					break;
 			if (i == mc->mc_top) {
 				/* There are no other pages */
 				mc->mc_ki[mc->mc_top] = nkeys;
 				return MDB_NOTFOUND;
 			}
 		}
 		if (!mc->mc_top) {
 			/* There are no other pages */
 			mc->mc_ki[mc->mc_top] = 0;
 			if (op == MDB_SET_RANGE && !exactp) {
 				rc = 0;
 				goto set1;
 			} else
 				return MDB_NOTFOUND;
 		}
 	} else {
 		mc->mc_pg[0] = 0;
 	}
 
 	rc = mdb_page_search(mc, key, 0);
 	if (rc != MDB_SUCCESS)
 		return rc;
 
 	mp = mc->mc_pg[mc->mc_top];
 	mdb_cassert(mc, IS_LEAF(mp));
 
 set2:
 	leaf = mdb_node_search(mc, key, exactp);
 	if (exactp != NULL && !*exactp) {
 		/* MDB_SET specified and not an exact match. */
 		return MDB_NOTFOUND;
 	}
 
 	if (leaf == NULL) {
 		DPUTS("===> inexact leaf not found, goto sibling");
 		if ((rc = mdb_cursor_sibling(mc, 1)) != MDB_SUCCESS) {
 			mc->mc_flags |= C_EOF;
 			return rc;		/* no entries matched */
 		}
 		mp = mc->mc_pg[mc->mc_top];
 		mdb_cassert(mc, IS_LEAF(mp));
 		leaf = NODEPTR(mp, 0);
 	}
 
 set1:
 	mc->mc_flags |= C_INITIALIZED;
 	mc->mc_flags &= ~C_EOF;
 
 	if (IS_LEAF2(mp)) {
 		if (op == MDB_SET_RANGE || op == MDB_SET_KEY) {
 			key->mv_size = mc->mc_db->md_pad;
 			key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
 		}
 		return MDB_SUCCESS;
 	}
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
 		if (op == MDB_SET || op == MDB_SET_KEY || op == MDB_SET_RANGE) {
 			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
 		} else {
 			int ex2, *ex2p;
 			if (op == MDB_GET_BOTH) {
 				ex2p = &ex2;
 				ex2 = 0;
 			} else {
 				ex2p = NULL;
 			}
 			rc = mdb_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_SET_RANGE, ex2p);
 			if (rc != MDB_SUCCESS)
 				return rc;
 		}
 	} else if (data) {
 		if (op == MDB_GET_BOTH || op == MDB_GET_BOTH_RANGE) {
 			MDB_val olddata;
 			MDB_cmp_func *dcmp;
 			if ((rc = mdb_node_read(mc, leaf, &olddata)) != MDB_SUCCESS)
 				return rc;
 			dcmp = mc->mc_dbx->md_dcmp;
 #if UINT_MAX < SIZE_MAX
 			if (dcmp == mdb_cmp_int && olddata.mv_size == sizeof(size_t))
 				dcmp = mdb_cmp_clong;
 #endif
 			rc = dcmp(data, &olddata);
 			if (rc) {
 				if (op == MDB_GET_BOTH || rc > 0)
 					return MDB_NOTFOUND;
 				rc = 0;
 			}
 			*data = olddata;
 
 		} else {
 			if (mc->mc_xcursor)
 				mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 				return rc;
 		}
 	}
 
 	/* The key already matches in all other cases */
 	if (op == MDB_SET_RANGE || op == MDB_SET_KEY)
 		MDB_GET_KEY(leaf, key);
 	DPRINTF(("==> cursor placed on key [%s]", DKEY(key)));
 
 	return rc;
 }
 
 /** Move the cursor to the first item in the database. */
 static int
 mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data)
 {
 	int		 rc;
 	MDB_node	*leaf;
 
 	if (mc->mc_xcursor)
 		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 
 	if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
 		rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
 		if (rc != MDB_SUCCESS)
 			return rc;
 	}
 	mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
 
 	leaf = NODEPTR(mc->mc_pg[mc->mc_top], 0);
 	mc->mc_flags |= C_INITIALIZED;
 	mc->mc_flags &= ~C_EOF;
 
 	mc->mc_ki[mc->mc_top] = 0;
 
 	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
 		if ( key ) {
 			key->mv_size = mc->mc_db->md_pad;
 			key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], 0, key->mv_size);
 		}
 		return MDB_SUCCESS;
 	}
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
 		rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
 		if (rc)
 			return rc;
 	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
 	}
 
 	MDB_GET_KEY(leaf, key);
 	return MDB_SUCCESS;
 }
 
 /** Move the cursor to the last item in the database. */
 static int
 mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data)
 {
 	int		 rc;
 	MDB_node	*leaf;
 
 	if (mc->mc_xcursor)
 		mc->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 
 	if (!(mc->mc_flags & C_INITIALIZED) || mc->mc_top) {
 		rc = mdb_page_search(mc, NULL, MDB_PS_LAST);
 		if (rc != MDB_SUCCESS)
 			return rc;
 	}
 	mdb_cassert(mc, IS_LEAF(mc->mc_pg[mc->mc_top]));
 
 	mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]) - 1;
 	mc->mc_flags |= C_INITIALIZED|C_EOF;
 	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 
 	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
 		if (key) {
 			key->mv_size = mc->mc_db->md_pad;
 			key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], key->mv_size);
 		}
 		return MDB_SUCCESS;
 	}
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
 		rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
 		if (rc)
 			return rc;
 	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
 	}
 
 	MDB_GET_KEY(leaf, key);
 	return MDB_SUCCESS;
 }
 
 int
 mdb_cursor_get(MDB_cursor *mc, MDB_val *key, MDB_val *data,
     MDB_cursor_op op)
 {
 	int		 rc;
 	int		 exact = 0;
 	int		 (*mfunc)(MDB_cursor *mc, MDB_val *key, MDB_val *data);
 
 	if (mc == NULL)
 		return EINVAL;
 
 	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	switch (op) {
 	case MDB_GET_CURRENT:
 		if (!(mc->mc_flags & C_INITIALIZED)) {
 			rc = EINVAL;
 		} else {
 			MDB_page *mp = mc->mc_pg[mc->mc_top];
 			int nkeys = NUMKEYS(mp);
 			if (!nkeys || mc->mc_ki[mc->mc_top] >= nkeys) {
 				mc->mc_ki[mc->mc_top] = nkeys;
 				rc = MDB_NOTFOUND;
 				break;
 			}
 			rc = MDB_SUCCESS;
 			if (IS_LEAF2(mp)) {
 				key->mv_size = mc->mc_db->md_pad;
 				key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
 			} else {
 				MDB_node *leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 				MDB_GET_KEY(leaf, key);
 				if (data) {
 					if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 						rc = mdb_cursor_get(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_GET_CURRENT);
 					} else {
 						rc = mdb_node_read(mc, leaf, data);
 					}
 				}
 			}
 		}
 		break;
 	case MDB_GET_BOTH:
 	case MDB_GET_BOTH_RANGE:
 		if (data == NULL) {
 			rc = EINVAL;
 			break;
 		}
 		if (mc->mc_xcursor == NULL) {
 			rc = MDB_INCOMPATIBLE;
 			break;
 		}
 		/* FALLTHRU */
 	case MDB_SET:
 	case MDB_SET_KEY:
 	case MDB_SET_RANGE:
 		if (key == NULL) {
 			rc = EINVAL;
 		} else {
 			rc = mdb_cursor_set(mc, key, data, op,
 				op == MDB_SET_RANGE ? NULL : &exact);
 		}
 		break;
 	case MDB_GET_MULTIPLE:
 		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
 			rc = EINVAL;
 			break;
 		}
 		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
 			rc = MDB_INCOMPATIBLE;
 			break;
 		}
 		rc = MDB_SUCCESS;
 		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) ||
 			(mc->mc_xcursor->mx_cursor.mc_flags & C_EOF))
 			break;
 		goto fetchm;
 	case MDB_NEXT_MULTIPLE:
 		if (data == NULL) {
 			rc = EINVAL;
 			break;
 		}
 		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
 			rc = MDB_INCOMPATIBLE;
 			break;
 		}
 		rc = mdb_cursor_next(mc, key, data, MDB_NEXT_DUP);
 		if (rc == MDB_SUCCESS) {
 			if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
 				MDB_cursor *mx;
 fetchm:
 				mx = &mc->mc_xcursor->mx_cursor;
 				data->mv_size = NUMKEYS(mx->mc_pg[mx->mc_top]) *
 					mx->mc_db->md_pad;
 				data->mv_data = METADATA(mx->mc_pg[mx->mc_top]);
 				mx->mc_ki[mx->mc_top] = NUMKEYS(mx->mc_pg[mx->mc_top])-1;
 			} else {
 				rc = MDB_NOTFOUND;
 			}
 		}
 		break;
 	case MDB_PREV_MULTIPLE:
 		if (data == NULL) {
 			rc = EINVAL;
 			break;
 		}
 		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
 			rc = MDB_INCOMPATIBLE;
 			break;
 		}
 		if (!(mc->mc_flags & C_INITIALIZED))
 			rc = mdb_cursor_last(mc, key, data);
 		else
 			rc = MDB_SUCCESS;
 		if (rc == MDB_SUCCESS) {
 			MDB_cursor *mx = &mc->mc_xcursor->mx_cursor;
 			if (mx->mc_flags & C_INITIALIZED) {
 				rc = mdb_cursor_sibling(mx, 0);
 				if (rc == MDB_SUCCESS)
 					goto fetchm;
 			} else {
 				rc = MDB_NOTFOUND;
 			}
 		}
 		break;
 	case MDB_NEXT:
 	case MDB_NEXT_DUP:
 	case MDB_NEXT_NODUP:
 		rc = mdb_cursor_next(mc, key, data, op);
 		break;
 	case MDB_PREV:
 	case MDB_PREV_DUP:
 	case MDB_PREV_NODUP:
 		rc = mdb_cursor_prev(mc, key, data, op);
 		break;
 	case MDB_FIRST:
 		rc = mdb_cursor_first(mc, key, data);
 		break;
 	case MDB_FIRST_DUP:
 		mfunc = mdb_cursor_first;
 	mmove:
 		if (data == NULL || !(mc->mc_flags & C_INITIALIZED)) {
 			rc = EINVAL;
 			break;
 		}
 		if (mc->mc_xcursor == NULL) {
 			rc = MDB_INCOMPATIBLE;
 			break;
 		}
 		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top])) {
 			mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]);
 			rc = MDB_NOTFOUND;
 			break;
 		}
 		mc->mc_flags &= ~C_EOF;
 		{
 			MDB_node *leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 				MDB_GET_KEY(leaf, key);
 				rc = mdb_node_read(mc, leaf, data);
 				break;
 			}
 		}
 		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED)) {
 			rc = EINVAL;
 			break;
 		}
 		rc = mfunc(&mc->mc_xcursor->mx_cursor, data, NULL);
 		break;
 	case MDB_LAST:
 		rc = mdb_cursor_last(mc, key, data);
 		break;
 	case MDB_LAST_DUP:
 		mfunc = mdb_cursor_last;
 		goto mmove;
 	default:
 		DPRINTF(("unhandled/unimplemented cursor operation %u", op));
 		rc = EINVAL;
 		break;
 	}
 
 	if (mc->mc_flags & C_DEL)
 		mc->mc_flags ^= C_DEL;
 
 	return rc;
 }
 
 /** Touch all the pages in the cursor stack. Set mc_top.
  *	Makes sure all the pages are writable, before attempting a write operation.
  * @param[in] mc The cursor to operate on.
  */
 static int
 mdb_cursor_touch(MDB_cursor *mc)
 {
 	int rc = MDB_SUCCESS;
 
 	if (mc->mc_dbi >= CORE_DBS && !(*mc->mc_dbflag & (DB_DIRTY|DB_DUPDATA))) {
 		/* Touch DB record of named DB */
 		MDB_cursor mc2;
 		MDB_xcursor mcx;
 		if (TXN_DBI_CHANGED(mc->mc_txn, mc->mc_dbi))
 			return MDB_BAD_DBI;
 		mdb_cursor_init(&mc2, mc->mc_txn, MAIN_DBI, &mcx);
 		rc = mdb_page_search(&mc2, &mc->mc_dbx->md_name, MDB_PS_MODIFY);
 		if (rc)
 			 return rc;
 		*mc->mc_dbflag |= DB_DIRTY;
 	}
 	mc->mc_top = 0;
 	if (mc->mc_snum) {
 		do {
 			rc = mdb_page_touch(mc);
 		} while (!rc && ++(mc->mc_top) < mc->mc_snum);
 		mc->mc_top = mc->mc_snum-1;
 	}
 	return rc;
 }
 
 /** Do not spill pages to disk if txn is getting full, may fail instead */
 #define MDB_NOSPILL	0x8000
 
 int
 mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
     unsigned int flags)
 {
 	MDB_env		*env;
 	MDB_node	*leaf = NULL;
 	MDB_page	*fp, *mp, *sub_root = NULL;
 	uint16_t	fp_flags;
 	MDB_val		xdata, *rdata, dkey, olddata;
 	MDB_db dummy;
 	int do_sub = 0, insert_key, insert_data;
 	unsigned int mcount = 0, dcount = 0, nospill;
 	size_t nsize;
 	int rc, rc2;
 	unsigned int nflags;
 	DKBUF;
 
 	if (mc == NULL || key == NULL)
 		return EINVAL;
 
 	env = mc->mc_txn->mt_env;
 
 	/* Check this first so counter will always be zero on any
 	 * early failures.
 	 */
 	if (flags & MDB_MULTIPLE) {
 		dcount = data[1].mv_size;
 		data[1].mv_size = 0;
 		if (!F_ISSET(mc->mc_db->md_flags, MDB_DUPFIXED))
 			return MDB_INCOMPATIBLE;
 	}
 
 	nospill = flags & MDB_NOSPILL;
 	flags &= ~MDB_NOSPILL;
 
 	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
 		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
 
 	if (key->mv_size-1 >= ENV_MAXKEY(env))
 		return MDB_BAD_VALSIZE;
 
 #if SIZE_MAX > MAXDATASIZE
 	if (data->mv_size > ((mc->mc_db->md_flags & MDB_DUPSORT) ? ENV_MAXKEY(env) : MAXDATASIZE))
 		return MDB_BAD_VALSIZE;
 #else
 	if ((mc->mc_db->md_flags & MDB_DUPSORT) && data->mv_size > ENV_MAXKEY(env))
 		return MDB_BAD_VALSIZE;
 #endif
 
 	DPRINTF(("==> put db %d key [%s], size %"Z"u, data size %"Z"u",
 		DDBI(mc), DKEY(key), key ? key->mv_size : 0, data->mv_size));
 
 	dkey.mv_size = 0;
 
 	if (flags & MDB_CURRENT) {
 		if (!(mc->mc_flags & C_INITIALIZED))
 			return EINVAL;
 		rc = MDB_SUCCESS;
 	} else if (mc->mc_db->md_root == P_INVALID) {
 		/* new database, cursor has nothing to point to */
 		mc->mc_snum = 0;
 		mc->mc_top = 0;
 		mc->mc_flags &= ~C_INITIALIZED;
 		rc = MDB_NO_ROOT;
 	} else {
 		int exact = 0;
 		MDB_val d2;
 		if (flags & MDB_APPEND) {
 			MDB_val k2;
 			rc = mdb_cursor_last(mc, &k2, &d2);
 			if (rc == 0) {
 				rc = mc->mc_dbx->md_cmp(key, &k2);
 				if (rc > 0) {
 					rc = MDB_NOTFOUND;
 					mc->mc_ki[mc->mc_top]++;
 				} else {
 					/* new key is <= last key */
 					rc = MDB_KEYEXIST;
 				}
 			}
 		} else {
 			rc = mdb_cursor_set(mc, key, &d2, MDB_SET, &exact);
 		}
 		if ((flags & MDB_NOOVERWRITE) && rc == 0) {
 			DPRINTF(("duplicate key [%s]", DKEY(key)));
 			*data = d2;
 			return MDB_KEYEXIST;
 		}
 		if (rc && rc != MDB_NOTFOUND)
 			return rc;
 	}
 
 	if (mc->mc_flags & C_DEL)
 		mc->mc_flags ^= C_DEL;
 
 	/* Cursor is positioned, check for room in the dirty list */
 	if (!nospill) {
 		if (flags & MDB_MULTIPLE) {
 			rdata = &xdata;
 			xdata.mv_size = data->mv_size * dcount;
 		} else {
 			rdata = data;
 		}
 		if ((rc2 = mdb_page_spill(mc, key, rdata)))
 			return rc2;
 	}
 
 	if (rc == MDB_NO_ROOT) {
 		MDB_page *np;
 		/* new database, write a root leaf page */
 		DPUTS("allocating new root leaf page");
 		if ((rc2 = mdb_page_new(mc, P_LEAF, 1, &np))) {
 			return rc2;
 		}
 		mdb_cursor_push(mc, np);
 		mc->mc_db->md_root = np->mp_pgno;
 		mc->mc_db->md_depth++;
 		*mc->mc_dbflag |= DB_DIRTY;
 		if ((mc->mc_db->md_flags & (MDB_DUPSORT|MDB_DUPFIXED))
 			== MDB_DUPFIXED)
 			MP_FLAGS(np) |= P_LEAF2;
 		mc->mc_flags |= C_INITIALIZED;
 	} else {
 		/* make sure all cursor pages are writable */
 		rc2 = mdb_cursor_touch(mc);
 		if (rc2)
 			return rc2;
 	}
 
 	insert_key = insert_data = rc;
 	if (insert_key) {
 		/* The key does not exist */
 		DPRINTF(("inserting key at index %i", mc->mc_ki[mc->mc_top]));
 		if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
 			LEAFSIZE(key, data) > env->me_nodemax)
 		{
 			/* Too big for a node, insert in sub-DB.  Set up an empty
 			 * "old sub-page" for prep_subDB to expand to a full page.
 			 */
 			fp_flags = P_LEAF|P_DIRTY;
 			fp = env->me_pbuf;
 			fp->mp_pad = data->mv_size; /* used if MDB_DUPFIXED */
 			MP_LOWER(fp) = MP_UPPER(fp) = (PAGEHDRSZ-PAGEBASE);
 			olddata.mv_size = PAGEHDRSZ;
 			goto prep_subDB;
 		}
 	} else {
 		/* there's only a key anyway, so this is a no-op */
 		if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
 			char *ptr;
 			unsigned int ksize = mc->mc_db->md_pad;
 			if (key->mv_size != ksize)
 				return MDB_BAD_VALSIZE;
 			ptr = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], ksize);
 			memcpy(ptr, key->mv_data, ksize);
 fix_parent:
 			/* if overwriting slot 0 of leaf, need to
 			 * update branch key if there is a parent page
 			 */
 			if (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
 				unsigned short dtop = 1;
 				mc->mc_top--;
 				/* slot 0 is always an empty key, find real slot */
 				while (mc->mc_top && !mc->mc_ki[mc->mc_top]) {
 					mc->mc_top--;
 					dtop++;
 				}
 				if (mc->mc_ki[mc->mc_top])
 					rc2 = mdb_update_key(mc, key);
 				else
 					rc2 = MDB_SUCCESS;
 				mc->mc_top += dtop;
 				if (rc2)
 					return rc2;
 			}
 			return MDB_SUCCESS;
 		}
 
 more:
 		leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 		olddata.mv_size = NODEDSZ(leaf);
 		olddata.mv_data = NODEDATA(leaf);
 
 		/* DB has dups? */
 		if (F_ISSET(mc->mc_db->md_flags, MDB_DUPSORT)) {
 			/* Prepare (sub-)page/sub-DB to accept the new item,
 			 * if needed.  fp: old sub-page or a header faking
 			 * it.  mp: new (sub-)page.  offset: growth in page
 			 * size.  xdata: node data with new page or DB.
 			 */
 			unsigned	i, offset = 0;
 			mp = fp = xdata.mv_data = env->me_pbuf;
 			mp->mp_pgno = mc->mc_pg[mc->mc_top]->mp_pgno;
 
 			/* Was a single item before, must convert now */
 			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 				MDB_cmp_func *dcmp;
 				/* Just overwrite the current item */
 				if (flags == MDB_CURRENT)
 					goto current;
 				dcmp = mc->mc_dbx->md_dcmp;
 #if UINT_MAX < SIZE_MAX
 				if (dcmp == mdb_cmp_int && olddata.mv_size == sizeof(size_t))
 					dcmp = mdb_cmp_clong;
 #endif
 				/* does data match? */
 				if (!dcmp(data, &olddata)) {
 					if (flags & (MDB_NODUPDATA|MDB_APPENDDUP))
 						return MDB_KEYEXIST;
 					/* overwrite it */
 					goto current;
 				}
 
 				/* Back up original data item */
 				dkey.mv_size = olddata.mv_size;
 				dkey.mv_data = memcpy(fp+1, olddata.mv_data, olddata.mv_size);
 
 				/* Make sub-page header for the dup items, with dummy body */
 				MP_FLAGS(fp) = P_LEAF|P_DIRTY|P_SUBP;
 				MP_LOWER(fp) = (PAGEHDRSZ-PAGEBASE);
 				xdata.mv_size = PAGEHDRSZ + dkey.mv_size + data->mv_size;
 				if (mc->mc_db->md_flags & MDB_DUPFIXED) {
 					MP_FLAGS(fp) |= P_LEAF2;
 					fp->mp_pad = data->mv_size;
 					xdata.mv_size += 2 * data->mv_size;	/* leave space for 2 more */
 				} else {
 					xdata.mv_size += 2 * (sizeof(indx_t) + NODESIZE) +
 						(dkey.mv_size & 1) + (data->mv_size & 1);
 				}
 				MP_UPPER(fp) = xdata.mv_size - PAGEBASE;
 				olddata.mv_size = xdata.mv_size; /* pretend olddata is fp */
 			} else if (leaf->mn_flags & F_SUBDATA) {
 				/* Data is on sub-DB, just store it */
 				flags |= F_DUPDATA|F_SUBDATA;
 				goto put_sub;
 			} else {
 				/* Data is on sub-page */
 				fp = olddata.mv_data;
 				switch (flags) {
 				default:
 					if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
 						offset = EVEN(NODESIZE + sizeof(indx_t) +
 							data->mv_size);
 						break;
 					}
 					offset = fp->mp_pad;
 					if (SIZELEFT(fp) < offset) {
 						offset *= 4; /* space for 4 more */
 						break;
 					}
 					/* FALLTHRU */ /* Big enough MDB_DUPFIXED sub-page */
 				case MDB_CURRENT:
 					MP_FLAGS(fp) |= P_DIRTY;
 					COPY_PGNO(MP_PGNO(fp), MP_PGNO(mp));
 					mc->mc_xcursor->mx_cursor.mc_pg[0] = fp;
 					flags |= F_DUPDATA;
 					goto put_sub;
 				}
 				xdata.mv_size = olddata.mv_size + offset;
 			}
 
 			fp_flags = MP_FLAGS(fp);
 			if (NODESIZE + NODEKSZ(leaf) + xdata.mv_size > env->me_nodemax) {
 					/* Too big for a sub-page, convert to sub-DB */
 					fp_flags &= ~P_SUBP;
 prep_subDB:
 					if (mc->mc_db->md_flags & MDB_DUPFIXED) {
 						fp_flags |= P_LEAF2;
 						dummy.md_pad = fp->mp_pad;
 						dummy.md_flags = MDB_DUPFIXED;
 						if (mc->mc_db->md_flags & MDB_INTEGERDUP)
 							dummy.md_flags |= MDB_INTEGERKEY;
 					} else {
 						dummy.md_pad = 0;
 						dummy.md_flags = 0;
 					}
 					dummy.md_depth = 1;
 					dummy.md_branch_pages = 0;
 					dummy.md_leaf_pages = 1;
 					dummy.md_overflow_pages = 0;
 					dummy.md_entries = NUMKEYS(fp);
 					xdata.mv_size = sizeof(MDB_db);
 					xdata.mv_data = &dummy;
 					if ((rc = mdb_page_alloc(mc, 1, &mp)))
 						return rc;
 					offset = env->me_psize - olddata.mv_size;
 					flags |= F_DUPDATA|F_SUBDATA;
 					dummy.md_root = mp->mp_pgno;
 					sub_root = mp;
 			}
 			if (mp != fp) {
 				MP_FLAGS(mp) = fp_flags | P_DIRTY;
 				MP_PAD(mp)   = MP_PAD(fp);
 				MP_LOWER(mp) = MP_LOWER(fp);
 				MP_UPPER(mp) = MP_UPPER(fp) + offset;
 				if (fp_flags & P_LEAF2) {
 					memcpy(METADATA(mp), METADATA(fp), NUMKEYS(fp) * fp->mp_pad);
 				} else {
 					memcpy((char *)mp + MP_UPPER(mp) + PAGEBASE, (char *)fp + MP_UPPER(fp) + PAGEBASE,
 						olddata.mv_size - MP_UPPER(fp) - PAGEBASE);
 					memcpy((char *)MP_PTRS(mp), (char *)MP_PTRS(fp), NUMKEYS(fp) * sizeof(mp->mp_ptrs[0]));
 					for (i=0; i<NUMKEYS(fp); i++)
 						mp->mp_ptrs[i] += offset;
 				}
 			}
 
 			rdata = &xdata;
 			flags |= F_DUPDATA;
 			do_sub = 1;
 			if (!insert_key)
 				mdb_node_del(mc, 0);
 			goto new_sub;
 		}
 current:
 		/* LMDB passes F_SUBDATA in 'flags' to write a DB record */
 		if ((leaf->mn_flags ^ flags) & F_SUBDATA)
 			return MDB_INCOMPATIBLE;
 		/* overflow page overwrites need special handling */
 		if (F_ISSET(leaf->mn_flags, F_BIGDATA)) {
 			MDB_page *omp;
 			pgno_t pg;
 			int level, ovpages, dpages = OVPAGES(data->mv_size, env->me_psize);
 
 			memcpy(&pg, olddata.mv_data, sizeof(pg));
 			if ((rc2 = mdb_page_get(mc, pg, &omp, &level)) != 0)
 				return rc2;
 			ovpages = omp->mp_pages;
 
 			/* Is the ov page large enough? */
 			if (ovpages >= dpages) {
 			  if (!(omp->mp_flags & P_DIRTY) &&
 				  (level || (env->me_flags & MDB_WRITEMAP)))
 			  {
 				rc = mdb_page_unspill(mc->mc_txn, omp, &omp);
 				if (rc)
 					return rc;
 				level = 0;		/* dirty in this txn or clean */
 			  }
 			  /* Is it dirty? */
 			  if (omp->mp_flags & P_DIRTY) {
 				/* yes, overwrite it. Note in this case we don't
 				 * bother to try shrinking the page if the new data
 				 * is smaller than the overflow threshold.
 				 */
 				if (level > 1) {
 					/* It is writable only in a parent txn */
 					size_t sz = (size_t) env->me_psize * ovpages, off;
 					MDB_page *np = mdb_page_malloc(mc->mc_txn, ovpages);
 					MDB_ID2 id2;
 					if (!np)
 						return ENOMEM;
 					id2.mid = pg;
 					id2.mptr = np;
 					/* Note - this page is already counted in parent's dirty_room */
 					rc2 = mdb_mid2l_insert(mc->mc_txn->mt_u.dirty_list, &id2);
 					mdb_cassert(mc, rc2 == 0);
 					/* Currently we make the page look as with put() in the
 					 * parent txn, in case the user peeks at MDB_RESERVEd
 					 * or unused parts. Some users treat ovpages specially.
 					 */
 					if (!(flags & MDB_RESERVE)) {
 						/* Skip the part where LMDB will put *data.
 						 * Copy end of page, adjusting alignment so
 						 * compiler may copy words instead of bytes.
 						 */
 						off = (PAGEHDRSZ + data->mv_size) & -(int)sizeof(size_t);
 						memcpy((size_t *)((char *)np + off),
 							(size_t *)((char *)omp + off), sz - off);
 						sz = PAGEHDRSZ;
 					}
 					memcpy(np, omp, sz); /* Copy beginning of page */
 					omp = np;
 				}
 				SETDSZ(leaf, data->mv_size);
 				if (F_ISSET(flags, MDB_RESERVE))
 					data->mv_data = METADATA(omp);
 				else
 					memcpy(METADATA(omp), data->mv_data, data->mv_size);
 				return MDB_SUCCESS;
 			  }
 			}
 			if ((rc2 = mdb_ovpage_free(mc, omp)) != MDB_SUCCESS)
 				return rc2;
 		} else if (data->mv_size == olddata.mv_size) {
 			/* same size, just replace it. Note that we could
 			 * also reuse this node if the new data is smaller,
 			 * but instead we opt to shrink the node in that case.
 			 */
 			if (F_ISSET(flags, MDB_RESERVE))
 				data->mv_data = olddata.mv_data;
 			else if (!(mc->mc_flags & C_SUB))
 				memcpy(olddata.mv_data, data->mv_data, data->mv_size);
 			else {
 				if (key->mv_size != NODEKSZ(leaf))
 					goto new_ksize;
 				memcpy(NODEKEY(leaf), key->mv_data, key->mv_size);
 				goto fix_parent;
 			}
 			return MDB_SUCCESS;
 		}
 new_ksize:
 		mdb_node_del(mc, 0);
 	}
 
 	rdata = data;
 
 new_sub:
 	nflags = flags & NODE_ADD_FLAGS;
 	nsize = IS_LEAF2(mc->mc_pg[mc->mc_top]) ? key->mv_size : mdb_leaf_size(env, key, rdata);
 	if (SIZELEFT(mc->mc_pg[mc->mc_top]) < nsize) {
 		if (( flags & (F_DUPDATA|F_SUBDATA)) == F_DUPDATA )
 			nflags &= ~MDB_APPEND; /* sub-page may need room to grow */
 		if (!insert_key)
 			nflags |= MDB_SPLIT_REPLACE;
 		rc = mdb_page_split(mc, key, rdata, P_INVALID, nflags);
 	} else {
 		/* There is room already in this leaf page. */
 		rc = mdb_node_add(mc, mc->mc_ki[mc->mc_top], key, rdata, 0, nflags);
 		if (rc == 0) {
 			/* Adjust other cursors pointing to mp */
 			MDB_cursor *m2, *m3;
 			MDB_dbi dbi = mc->mc_dbi;
 			unsigned i = mc->mc_top;
 			MDB_page *mp = mc->mc_pg[i];
 
 			for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 				if (mc->mc_flags & C_SUB)
 					m3 = &m2->mc_xcursor->mx_cursor;
 				else
 					m3 = m2;
 				if (m3 == mc || m3->mc_snum < mc->mc_snum || m3->mc_pg[i] != mp) continue;
 				if (m3->mc_ki[i] >= mc->mc_ki[i] && insert_key) {
 					m3->mc_ki[i]++;
 				}
 				XCURSOR_REFRESH(m3, i, mp);
 			}
 		}
 	}
 
 	if (rc == MDB_SUCCESS) {
 		/* Now store the actual data in the child DB. Note that we're
 		 * storing the user data in the keys field, so there are strict
 		 * size limits on dupdata. The actual data fields of the child
 		 * DB are all zero size.
 		 */
 		if (do_sub) {
 			int xflags, new_dupdata;
 			size_t ecount;
 put_sub:
 			xdata.mv_size = 0;
 			xdata.mv_data = "";
 			leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 			if ((flags & (MDB_CURRENT|MDB_APPENDDUP)) == MDB_CURRENT) {
 				xflags = MDB_CURRENT|MDB_NOSPILL;
 			} else {
 				mdb_xcursor_init1(mc, leaf);
 				xflags = (flags & MDB_NODUPDATA) ?
 					MDB_NOOVERWRITE|MDB_NOSPILL : MDB_NOSPILL;
 			}
 			if (sub_root)
 				mc->mc_xcursor->mx_cursor.mc_pg[0] = sub_root;
 			new_dupdata = (int)dkey.mv_size;
 			/* converted, write the original data first */
 			if (dkey.mv_size) {
 				rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, &dkey, &xdata, xflags);
 				if (rc)
 					goto bad_sub;
 				/* we've done our job */
 				dkey.mv_size = 0;
 			}
 			if (!(leaf->mn_flags & F_SUBDATA) || sub_root) {
 				/* Adjust other cursors pointing to mp */
 				MDB_cursor *m2;
 				MDB_xcursor *mx = mc->mc_xcursor;
 				unsigned i = mc->mc_top;
 				MDB_page *mp = mc->mc_pg[i];
 
 				for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
 					if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
 					if (!(m2->mc_flags & C_INITIALIZED)) continue;
 					if (m2->mc_pg[i] == mp) {
 						if (m2->mc_ki[i] == mc->mc_ki[i]) {
 							mdb_xcursor_init2(m2, mx, new_dupdata);
 						} else if (!insert_key) {
 							XCURSOR_REFRESH(m2, i, mp);
 						}
 					}
 				}
 			}
 			ecount = mc->mc_xcursor->mx_db.md_entries;
 			if (flags & MDB_APPENDDUP)
 				xflags |= MDB_APPEND;
 			rc = mdb_cursor_put(&mc->mc_xcursor->mx_cursor, data, &xdata, xflags);
 			if (flags & F_SUBDATA) {
 				void *db = NODEDATA(leaf);
 				memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
 			}
 			insert_data = mc->mc_xcursor->mx_db.md_entries - ecount;
 		}
 		/* Increment count unless we just replaced an existing item. */
 		if (insert_data)
 			mc->mc_db->md_entries++;
 		if (insert_key) {
 			/* Invalidate txn if we created an empty sub-DB */
 			if (rc)
 				goto bad_sub;
 			/* If we succeeded and the key didn't exist before,
 			 * make sure the cursor is marked valid.
 			 */
 			mc->mc_flags |= C_INITIALIZED;
 		}
 		if (flags & MDB_MULTIPLE) {
 			if (!rc) {
 				mcount++;
 				/* let caller know how many succeeded, if any */
 				data[1].mv_size = mcount;
 				if (mcount < dcount) {
 					data[0].mv_data = (char *)data[0].mv_data + data[0].mv_size;
 					insert_key = insert_data = 0;
 					goto more;
 				}
 			}
 		}
 		return rc;
 bad_sub:
 		if (rc == MDB_KEYEXIST)	/* should not happen, we deleted that item */
 			rc = MDB_CORRUPTED;
 	}
 	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 int
 mdb_cursor_del(MDB_cursor *mc, unsigned int flags)
 {
 	MDB_node	*leaf;
 	MDB_page	*mp;
 	int rc;
 
 	if (mc->mc_txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
 		return (mc->mc_txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
 
 	if (!(mc->mc_flags & C_INITIALIZED))
 		return EINVAL;
 
 	if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top]))
 		return MDB_NOTFOUND;
 
 	if (!(flags & MDB_NOSPILL) && (rc = mdb_page_spill(mc, NULL, NULL)))
 		return rc;
 
 	rc = mdb_cursor_touch(mc);
 	if (rc)
 		return rc;
 
 	mp = mc->mc_pg[mc->mc_top];
 	if (!IS_LEAF(mp))
 		return MDB_CORRUPTED;
 	if (IS_LEAF2(mp))
 		goto del_key;
 	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		if (flags & MDB_NODUPDATA) {
 			/* mdb_cursor_del0() will subtract the final entry */
 			mc->mc_db->md_entries -= mc->mc_xcursor->mx_db.md_entries - 1;
 			mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
 		} else {
 			if (!F_ISSET(leaf->mn_flags, F_SUBDATA)) {
 				mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
 			}
 			rc = mdb_cursor_del(&mc->mc_xcursor->mx_cursor, MDB_NOSPILL);
 			if (rc)
 				return rc;
 			/* If sub-DB still has entries, we're done */
 			if (mc->mc_xcursor->mx_db.md_entries) {
 				if (leaf->mn_flags & F_SUBDATA) {
 					/* update subDB info */
 					void *db = NODEDATA(leaf);
 					memcpy(db, &mc->mc_xcursor->mx_db, sizeof(MDB_db));
 				} else {
 					MDB_cursor *m2;
 					/* shrink fake page */
 					mdb_node_shrink(mp, mc->mc_ki[mc->mc_top]);
 					leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 					mc->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(leaf);
 					/* fix other sub-DB cursors pointed at fake pages on this page */
 					for (m2 = mc->mc_txn->mt_cursors[mc->mc_dbi]; m2; m2=m2->mc_next) {
 						if (m2 == mc || m2->mc_snum < mc->mc_snum) continue;
 						if (!(m2->mc_flags & C_INITIALIZED)) continue;
 						if (m2->mc_pg[mc->mc_top] == mp) {
 							XCURSOR_REFRESH(m2, mc->mc_top, mp);
 						}
 					}
 				}
 				mc->mc_db->md_entries--;
 				return rc;
 			} else {
 				mc->mc_xcursor->mx_cursor.mc_flags &= ~C_INITIALIZED;
 			}
 			/* otherwise fall thru and delete the sub-DB */
 		}
 
 		if (leaf->mn_flags & F_SUBDATA) {
 			/* add all the child DB's pages to the free list */
 			rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
 			if (rc)
 				goto fail;
 		}
 	}
 	/* LMDB passes F_SUBDATA in 'flags' to delete a DB record */
 	else if ((leaf->mn_flags ^ flags) & F_SUBDATA) {
 		rc = MDB_INCOMPATIBLE;
 		goto fail;
 	}
 
 	/* add overflow pages to free list */
 	if (F_ISSET(leaf->mn_flags, F_BIGDATA)) {
 		MDB_page *omp;
 		pgno_t pg;
 
 		memcpy(&pg, NODEDATA(leaf), sizeof(pg));
 		if ((rc = mdb_page_get(mc, pg, &omp, NULL)) ||
 			(rc = mdb_ovpage_free(mc, omp)))
 			goto fail;
 	}
 
 del_key:
 	return mdb_cursor_del0(mc);
 
 fail:
 	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 /** Allocate and initialize new pages for a database.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in] mc a cursor on the database being added to.
  * @param[in] flags flags defining what type of page is being allocated.
  * @param[in] num the number of pages to allocate. This is usually 1,
  * unless allocating overflow pages for a large record.
  * @param[out] mp Address of a page, or NULL on failure.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_new(MDB_cursor *mc, uint32_t flags, int num, MDB_page **mp)
 {
 	MDB_page	*np;
 	int rc;
 
 	if ((rc = mdb_page_alloc(mc, num, &np)))
 		return rc;
 	DPRINTF(("allocated new mpage %"Z"u, page size %u",
 	    np->mp_pgno, mc->mc_txn->mt_env->me_psize));
 	np->mp_flags = flags | P_DIRTY;
 	np->mp_lower = (PAGEHDRSZ-PAGEBASE);
 	np->mp_upper = mc->mc_txn->mt_env->me_psize - PAGEBASE;
 
 	if (IS_BRANCH(np))
 		mc->mc_db->md_branch_pages++;
 	else if (IS_LEAF(np))
 		mc->mc_db->md_leaf_pages++;
 	else if (IS_OVERFLOW(np)) {
 		mc->mc_db->md_overflow_pages += num;
 		np->mp_pages = num;
 	}
 	*mp = np;
 
 	return 0;
 }
 
 /** Calculate the size of a leaf node.
  * The size depends on the environment's page size; if a data item
  * is too large it will be put onto an overflow page and the node
  * size will only include the key and not the data. Sizes are always
  * rounded up to an even number of bytes, to guarantee 2-byte alignment
  * of the #MDB_node headers.
  * @param[in] env The environment handle.
  * @param[in] key The key for the node.
  * @param[in] data The data for the node.
  * @return The number of bytes needed to store the node.
  */
 static size_t
 mdb_leaf_size(MDB_env *env, MDB_val *key, MDB_val *data)
 {
 	size_t		 sz;
 
 	sz = LEAFSIZE(key, data);
 	if (sz > env->me_nodemax) {
 		/* put on overflow page */
 		sz -= data->mv_size - sizeof(pgno_t);
 	}
 
 	return EVEN(sz + sizeof(indx_t));
 }
 
 /** Calculate the size of a branch node.
  * The size should depend on the environment's page size but since
  * we currently don't support spilling large keys onto overflow
  * pages, it's simply the size of the #MDB_node header plus the
  * size of the key. Sizes are always rounded up to an even number
  * of bytes, to guarantee 2-byte alignment of the #MDB_node headers.
  * @param[in] env The environment handle.
  * @param[in] key The key for the node.
  * @return The number of bytes needed to store the node.
  */
 static size_t
 mdb_branch_size(MDB_env *env, MDB_val *key)
 {
 	size_t		 sz;
 
 	sz = INDXSIZE(key);
 	if (sz > env->me_nodemax) {
 		/* put on overflow page */
 		/* not implemented */
 		/* sz -= key->size - sizeof(pgno_t); */
 	}
 
 	return sz + sizeof(indx_t);
 }
 
 /** Add a node to the page pointed to by the cursor.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in] mc The cursor for this operation.
  * @param[in] indx The index on the page where the new node should be added.
  * @param[in] key The key for the new node.
  * @param[in] data The data for the new node, if any.
  * @param[in] pgno The page number, if adding a branch node.
  * @param[in] flags Flags for the node.
  * @return 0 on success, non-zero on failure. Possible errors are:
  * <ul>
  *	<li>ENOMEM - failed to allocate overflow pages for the node.
  *	<li>MDB_PAGE_FULL - there is insufficient room in the page. This error
  *	should never happen since all callers already calculate the
  *	page's free space before calling this function.
  * </ul>
  */
 static int
 mdb_node_add(MDB_cursor *mc, indx_t indx,
     MDB_val *key, MDB_val *data, pgno_t pgno, unsigned int flags)
 {
 	unsigned int	 i;
 	size_t		 node_size = NODESIZE;
 	ssize_t		 room;
 	indx_t		 ofs;
 	MDB_node	*node;
 	MDB_page	*mp = mc->mc_pg[mc->mc_top];
 	MDB_page	*ofp = NULL;		/* overflow page */
 	void		*ndata;
 	DKBUF;
 
 	mdb_cassert(mc, MP_UPPER(mp) >= MP_LOWER(mp));
 
 	DPRINTF(("add to %s %spage %"Z"u index %i, data size %"Z"u key size %"Z"u [%s]",
 	    IS_LEAF(mp) ? "leaf" : "branch",
 		IS_SUBP(mp) ? "sub-" : "",
 		mdb_dbg_pgno(mp), indx, data ? data->mv_size : 0,
 		key ? key->mv_size : 0, key ? DKEY(key) : "null"));
 
 	if (IS_LEAF2(mp)) {
 		/* Move higher keys up one slot. */
 		int ksize = mc->mc_db->md_pad, dif;
 		char *ptr = LEAF2KEY(mp, indx, ksize);
 		dif = NUMKEYS(mp) - indx;
 		if (dif > 0)
 			memmove(ptr+ksize, ptr, dif*ksize);
 		/* insert new key */
 		memcpy(ptr, key->mv_data, ksize);
 
 		/* Just using these for counting */
 		MP_LOWER(mp) += sizeof(indx_t);
 		MP_UPPER(mp) -= ksize - sizeof(indx_t);
 		return MDB_SUCCESS;
 	}
 
 	room = (ssize_t)SIZELEFT(mp) - (ssize_t)sizeof(indx_t);
 	if (key != NULL)
 		node_size += key->mv_size;
 	if (IS_LEAF(mp)) {
 		mdb_cassert(mc, key && data);
 		if (F_ISSET(flags, F_BIGDATA)) {
 			/* Data already on overflow page. */
 			node_size += sizeof(pgno_t);
 		} else if (node_size + data->mv_size > mc->mc_txn->mt_env->me_nodemax) {
 			int ovpages = OVPAGES(data->mv_size, mc->mc_txn->mt_env->me_psize);
 			int rc;
 			/* Put data on overflow page. */
 			DPRINTF(("data size is %"Z"u, node would be %"Z"u, put data on overflow page",
 			    data->mv_size, node_size+data->mv_size));
 			node_size = EVEN(node_size + sizeof(pgno_t));
 			if ((ssize_t)node_size > room)
 				goto full;
 			if ((rc = mdb_page_new(mc, P_OVERFLOW, ovpages, &ofp)))
 				return rc;
 			DPRINTF(("allocated overflow page %"Z"u", ofp->mp_pgno));
 			flags |= F_BIGDATA;
 			goto update;
 		} else {
 			node_size += data->mv_size;
 		}
 	}
 	node_size = EVEN(node_size);
 	if ((ssize_t)node_size > room)
 		goto full;
 
 update:
 	/* Move higher pointers up one slot. */
 	for (i = NUMKEYS(mp); i > indx; i--)
 		MP_PTRS(mp)[i] = MP_PTRS(mp)[i - 1];
 
 	/* Adjust free space offsets. */
 	ofs = MP_UPPER(mp) - node_size;
 	mdb_cassert(mc, ofs >= MP_LOWER(mp) + sizeof(indx_t));
 	MP_PTRS(mp)[indx] = ofs;
 	MP_UPPER(mp) = ofs;
 	MP_LOWER(mp) += sizeof(indx_t);
 
 	/* Write the node data. */
 	node = NODEPTR(mp, indx);
 	node->mn_ksize = (key == NULL) ? 0 : key->mv_size;
 	node->mn_flags = flags;
 	if (IS_LEAF(mp))
 		SETDSZ(node,data->mv_size);
 	else
 		SETPGNO(node,pgno);
 
 	if (key)
 		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
 
 	if (IS_LEAF(mp)) {
 		ndata = NODEDATA(node);
 		if (ofp == NULL) {
 			if (F_ISSET(flags, F_BIGDATA))
 				memcpy(ndata, data->mv_data, sizeof(pgno_t));
 			else if (F_ISSET(flags, MDB_RESERVE))
 				data->mv_data = ndata;
 			else
 				memcpy(ndata, data->mv_data, data->mv_size);
 		} else {
 			memcpy(ndata, &ofp->mp_pgno, sizeof(pgno_t));
 			ndata = METADATA(ofp);
 			if (F_ISSET(flags, MDB_RESERVE))
 				data->mv_data = ndata;
 			else
 				memcpy(ndata, data->mv_data, data->mv_size);
 		}
 	}
 
 	return MDB_SUCCESS;
 
 full:
 	DPRINTF(("not enough room in page %"Z"u, got %u ptrs",
 		mdb_dbg_pgno(mp), NUMKEYS(mp)));
 	DPRINTF(("upper-lower = %u - %u = %"Z"d", MP_UPPER(mp),MP_LOWER(mp),room));
 	DPRINTF(("node size = %"Z"u", node_size));
 	mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return MDB_PAGE_FULL;
 }
 
 /** Delete the specified node from a page.
  * @param[in] mc Cursor pointing to the node to delete.
  * @param[in] ksize The size of a node. Only used if the page is
  * part of a #MDB_DUPFIXED database.
  */
 static void
 mdb_node_del(MDB_cursor *mc, int ksize)
 {
 	MDB_page *mp = mc->mc_pg[mc->mc_top];
 	indx_t	indx = mc->mc_ki[mc->mc_top];
 	unsigned int	 sz;
 	indx_t		 i, j, numkeys, ptr;
 	MDB_node	*node;
 	char		*base;
 
 	DPRINTF(("delete node %u on %s page %"Z"u", indx,
 	    IS_LEAF(mp) ? "leaf" : "branch", mdb_dbg_pgno(mp)));
 	numkeys = NUMKEYS(mp);
 	mdb_cassert(mc, indx < numkeys);
 
 	if (IS_LEAF2(mp)) {
 		int x = numkeys - 1 - indx;
 		base = LEAF2KEY(mp, indx, ksize);
 		if (x)
 			memmove(base, base + ksize, x * ksize);
 		MP_LOWER(mp) -= sizeof(indx_t);
 		MP_UPPER(mp) += ksize - sizeof(indx_t);
 		return;
 	}
 
 	node = NODEPTR(mp, indx);
 	sz = NODESIZE + node->mn_ksize;
 	if (IS_LEAF(mp)) {
 		if (F_ISSET(node->mn_flags, F_BIGDATA))
 			sz += sizeof(pgno_t);
 		else
 			sz += NODEDSZ(node);
 	}
 	sz = EVEN(sz);
 
 	ptr = MP_PTRS(mp)[indx];
 	for (i = j = 0; i < numkeys; i++) {
 		if (i != indx) {
 			MP_PTRS(mp)[j] = MP_PTRS(mp)[i];
 			if (MP_PTRS(mp)[i] < ptr)
 				MP_PTRS(mp)[j] += sz;
 			j++;
 		}
 	}
 
 	base = (char *)mp + MP_UPPER(mp) + PAGEBASE;
 	memmove(base + sz, base, ptr - MP_UPPER(mp));
 
 	MP_LOWER(mp) -= sizeof(indx_t);
 	MP_UPPER(mp) += sz;
 }
 
 /** Compact the main page after deleting a node on a subpage.
  * @param[in] mp The main page to operate on.
  * @param[in] indx The index of the subpage on the main page.
  */
 static void
 mdb_node_shrink(MDB_page *mp, indx_t indx)
 {
 	MDB_node *node;
 	MDB_page *sp, *xp;
 	char *base;
 	indx_t delta, nsize, len, ptr;
 	int i;
 
 	node = NODEPTR(mp, indx);
 	sp = (MDB_page *)NODEDATA(node);
 	delta = SIZELEFT(sp);
 	nsize = NODEDSZ(node) - delta;
 
 	/* Prepare to shift upward, set len = length(subpage part to shift) */
 	if (IS_LEAF2(sp)) {
 		len = nsize;
 		if (nsize & 1)
 			return;		/* do not make the node uneven-sized */
 	} else {
 		xp = (MDB_page *)((char *)sp + delta); /* destination subpage */
 		for (i = NUMKEYS(sp); --i >= 0; )
 			MP_PTRS(xp)[i] = MP_PTRS(sp)[i] - delta;
 		len = PAGEHDRSZ;
 	}
 	MP_UPPER(sp) = MP_LOWER(sp);
 	COPY_PGNO(MP_PGNO(sp), mp->mp_pgno);
 	SETDSZ(node, nsize);
 
 	/* Shift <lower nodes...initial part of subpage> upward */
 	base = (char *)mp + mp->mp_upper + PAGEBASE;
 	memmove(base + delta, base, (char *)sp + len - base);
 
 	ptr = mp->mp_ptrs[indx];
 	for (i = NUMKEYS(mp); --i >= 0; ) {
 		if (mp->mp_ptrs[i] <= ptr)
 			mp->mp_ptrs[i] += delta;
 	}
 	mp->mp_upper += delta;
 }
 
 /** Initial setup of a sorted-dups cursor.
  * Sorted duplicates are implemented as a sub-database for the given key.
  * The duplicate data items are actually keys of the sub-database.
  * Operations on the duplicate data items are performed using a sub-cursor
  * initialized when the sub-database is first accessed. This function does
  * the preliminary setup of the sub-cursor, filling in the fields that
  * depend only on the parent DB.
  * @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
  */
 static void
 mdb_xcursor_init0(MDB_cursor *mc)
 {
 	MDB_xcursor *mx = mc->mc_xcursor;
 
 	mx->mx_cursor.mc_xcursor = NULL;
 	mx->mx_cursor.mc_txn = mc->mc_txn;
 	mx->mx_cursor.mc_db = &mx->mx_db;
 	mx->mx_cursor.mc_dbx = &mx->mx_dbx;
 	mx->mx_cursor.mc_dbi = mc->mc_dbi;
 	mx->mx_cursor.mc_dbflag = &mx->mx_dbflag;
 	mx->mx_cursor.mc_snum = 0;
 	mx->mx_cursor.mc_top = 0;
 	mx->mx_cursor.mc_flags = C_SUB;
 	mx->mx_dbx.md_name.mv_size = 0;
 	mx->mx_dbx.md_name.mv_data = NULL;
 	mx->mx_dbx.md_cmp = mc->mc_dbx->md_dcmp;
 	mx->mx_dbx.md_dcmp = NULL;
 	mx->mx_dbx.md_rel = mc->mc_dbx->md_rel;
 }
 
 /** Final setup of a sorted-dups cursor.
  *	Sets up the fields that depend on the data from the main cursor.
  * @param[in] mc The main cursor whose sorted-dups cursor is to be initialized.
  * @param[in] node The data containing the #MDB_db record for the
  * sorted-dup database.
  */
 static void
 mdb_xcursor_init1(MDB_cursor *mc, MDB_node *node)
 {
 	MDB_xcursor *mx = mc->mc_xcursor;
 
 	if (node->mn_flags & F_SUBDATA) {
 		memcpy(&mx->mx_db, NODEDATA(node), sizeof(MDB_db));
 		mx->mx_cursor.mc_pg[0] = 0;
 		mx->mx_cursor.mc_snum = 0;
 		mx->mx_cursor.mc_top = 0;
 		mx->mx_cursor.mc_flags = C_SUB;
 	} else {
 		MDB_page *fp = NODEDATA(node);
 		mx->mx_db.md_pad = 0;
 		mx->mx_db.md_flags = 0;
 		mx->mx_db.md_depth = 1;
 		mx->mx_db.md_branch_pages = 0;
 		mx->mx_db.md_leaf_pages = 1;
 		mx->mx_db.md_overflow_pages = 0;
 		mx->mx_db.md_entries = NUMKEYS(fp);
 		COPY_PGNO(mx->mx_db.md_root, MP_PGNO(fp));
 		mx->mx_cursor.mc_snum = 1;
 		mx->mx_cursor.mc_top = 0;
 		mx->mx_cursor.mc_flags = C_INITIALIZED|C_SUB;
 		mx->mx_cursor.mc_pg[0] = fp;
 		mx->mx_cursor.mc_ki[0] = 0;
 		if (mc->mc_db->md_flags & MDB_DUPFIXED) {
 			mx->mx_db.md_flags = MDB_DUPFIXED;
 			mx->mx_db.md_pad = fp->mp_pad;
 			if (mc->mc_db->md_flags & MDB_INTEGERDUP)
 				mx->mx_db.md_flags |= MDB_INTEGERKEY;
 		}
 	}
 	DPRINTF(("Sub-db -%u root page %"Z"u", mx->mx_cursor.mc_dbi,
 		mx->mx_db.md_root));
 	mx->mx_dbflag = DB_VALID|DB_USRVALID|DB_DUPDATA;
 #if UINT_MAX < SIZE_MAX
 	if (mx->mx_dbx.md_cmp == mdb_cmp_int && mx->mx_db.md_pad == sizeof(size_t))
 		mx->mx_dbx.md_cmp = mdb_cmp_clong;
 #endif
 }
 
 
 /** Fixup a sorted-dups cursor due to underlying update.
  *	Sets up some fields that depend on the data from the main cursor.
  *	Almost the same as init1, but skips initialization steps if the
  *	xcursor had already been used.
  * @param[in] mc The main cursor whose sorted-dups cursor is to be fixed up.
  * @param[in] src_mx The xcursor of an up-to-date cursor.
  * @param[in] new_dupdata True if converting from a non-#F_DUPDATA item.
  */
 static void
 mdb_xcursor_init2(MDB_cursor *mc, MDB_xcursor *src_mx, int new_dupdata)
 {
 	MDB_xcursor *mx = mc->mc_xcursor;
 
 	if (new_dupdata) {
 		mx->mx_cursor.mc_snum = 1;
 		mx->mx_cursor.mc_top = 0;
 		mx->mx_cursor.mc_flags |= C_INITIALIZED;
 		mx->mx_cursor.mc_ki[0] = 0;
 		mx->mx_dbflag = DB_VALID|DB_USRVALID|DB_DUPDATA;
 #if UINT_MAX < SIZE_MAX
 		mx->mx_dbx.md_cmp = src_mx->mx_dbx.md_cmp;
 #endif
 	} else if (!(mx->mx_cursor.mc_flags & C_INITIALIZED)) {
 		return;
 	}
 	mx->mx_db = src_mx->mx_db;
 	mx->mx_cursor.mc_pg[0] = src_mx->mx_cursor.mc_pg[0];
 	DPRINTF(("Sub-db -%u root page %"Z"u", mx->mx_cursor.mc_dbi,
 		mx->mx_db.md_root));
 }
 
 /** Initialize a cursor for a given transaction and database. */
 static void
 mdb_cursor_init(MDB_cursor *mc, MDB_txn *txn, MDB_dbi dbi, MDB_xcursor *mx)
 {
 	mc->mc_next = NULL;
 	mc->mc_backup = NULL;
 	mc->mc_dbi = dbi;
 	mc->mc_txn = txn;
 	mc->mc_db = &txn->mt_dbs[dbi];
 	mc->mc_dbx = &txn->mt_dbxs[dbi];
 	mc->mc_dbflag = &txn->mt_dbflags[dbi];
 	mc->mc_snum = 0;
 	mc->mc_top = 0;
 	mc->mc_pg[0] = 0;
 	mc->mc_ki[0] = 0;
 	mc->mc_flags = 0;
 	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT) {
 		mdb_tassert(txn, mx != NULL);
 		mc->mc_xcursor = mx;
 		mdb_xcursor_init0(mc);
 	} else {
 		mc->mc_xcursor = NULL;
 	}
 	if (*mc->mc_dbflag & DB_STALE) {
 		mdb_page_search(mc, NULL, MDB_PS_ROOTONLY);
 	}
 }
 
 int
 mdb_cursor_open(MDB_txn *txn, MDB_dbi dbi, MDB_cursor **ret)
 {
 	MDB_cursor	*mc;
 	size_t size = sizeof(MDB_cursor);
 
 	if (!ret || !TXN_DBI_EXIST(txn, dbi, DB_VALID))
 		return EINVAL;
 
 	if (txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	if (dbi == FREE_DBI && !F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
 		return EINVAL;
 
 	if (txn->mt_dbs[dbi].md_flags & MDB_DUPSORT)
 		size += sizeof(MDB_xcursor);
 
 	if ((mc = malloc(size)) != NULL) {
 		mdb_cursor_init(mc, txn, dbi, (MDB_xcursor *)(mc + 1));
 		if (txn->mt_cursors) {
 			mc->mc_next = txn->mt_cursors[dbi];
 			txn->mt_cursors[dbi] = mc;
 			mc->mc_flags |= C_UNTRACK;
 		}
 	} else {
 		return ENOMEM;
 	}
 
 	*ret = mc;
 
 	return MDB_SUCCESS;
 }
 
 int
 mdb_cursor_renew(MDB_txn *txn, MDB_cursor *mc)
 {
 	if (!mc || !TXN_DBI_EXIST(txn, mc->mc_dbi, DB_VALID))
 		return EINVAL;
 
 	if ((mc->mc_flags & C_UNTRACK) || txn->mt_cursors)
 		return EINVAL;
 
 	if (txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	mdb_cursor_init(mc, txn, mc->mc_dbi, mc->mc_xcursor);
 	return MDB_SUCCESS;
 }
 
 /* Return the count of duplicate data items for the current key */
 int
 mdb_cursor_count(MDB_cursor *mc, size_t *countp)
 {
 	MDB_node	*leaf;
 
 	if (mc == NULL || countp == NULL)
 		return EINVAL;
 
 	if (mc->mc_xcursor == NULL)
 		return MDB_INCOMPATIBLE;
 
 	if (mc->mc_txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	if (!(mc->mc_flags & C_INITIALIZED))
 		return EINVAL;
 
 	if (!mc->mc_snum)
 		return MDB_NOTFOUND;
 
 	if (mc->mc_flags & C_EOF) {
 		if (mc->mc_ki[mc->mc_top] >= NUMKEYS(mc->mc_pg[mc->mc_top]))
 			return MDB_NOTFOUND;
 		mc->mc_flags ^= C_EOF;
 	}
 
 	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 	if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		*countp = 1;
 	} else {
 		if (!(mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED))
 			return EINVAL;
 
 		*countp = mc->mc_xcursor->mx_db.md_entries;
 	}
 	return MDB_SUCCESS;
 }
 
 void
 mdb_cursor_close(MDB_cursor *mc)
 {
 	if (mc && !mc->mc_backup) {
 		/* remove from txn, if tracked */
 		if ((mc->mc_flags & C_UNTRACK) && mc->mc_txn->mt_cursors) {
 			MDB_cursor **prev = &mc->mc_txn->mt_cursors[mc->mc_dbi];
 			while (*prev && *prev != mc) prev = &(*prev)->mc_next;
 			if (*prev == mc)
 				*prev = mc->mc_next;
 		}
 		free(mc);
 	}
 }
 
 MDB_txn *
 mdb_cursor_txn(MDB_cursor *mc)
 {
 	if (!mc) return NULL;
 	return mc->mc_txn;
 }
 
 MDB_dbi
 mdb_cursor_dbi(MDB_cursor *mc)
 {
 	return mc->mc_dbi;
 }
 
 /** Replace the key for a branch node with a new key.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in] mc Cursor pointing to the node to operate on.
  * @param[in] key The new key to use.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_update_key(MDB_cursor *mc, MDB_val *key)
 {
 	MDB_page		*mp;
 	MDB_node		*node;
 	char			*base;
 	size_t			 len;
 	int				 delta, ksize, oksize;
 	indx_t			 ptr, i, numkeys, indx;
 	DKBUF;
 
 	indx = mc->mc_ki[mc->mc_top];
 	mp = mc->mc_pg[mc->mc_top];
 	node = NODEPTR(mp, indx);
 	ptr = mp->mp_ptrs[indx];
 #if MDB_DEBUG
 	{
 		MDB_val	k2;
 		char kbuf2[DKBUF_MAXKEYSIZE*2+1];
 		k2.mv_data = NODEKEY(node);
 		k2.mv_size = node->mn_ksize;
 		DPRINTF(("update key %u (ofs %u) [%s] to [%s] on page %"Z"u",
 			indx, ptr,
 			mdb_dkey(&k2, kbuf2),
 			DKEY(key),
 			mp->mp_pgno));
 	}
 #endif
 
 	/* Sizes must be 2-byte aligned. */
 	ksize = EVEN(key->mv_size);
 	oksize = EVEN(node->mn_ksize);
 	delta = ksize - oksize;
 
 	/* Shift node contents if EVEN(key length) changed. */
 	if (delta) {
 		if (delta > 0 && SIZELEFT(mp) < delta) {
 			pgno_t pgno;
 			/* not enough space left, do a delete and split */
 			DPRINTF(("Not enough room, delta = %d, splitting...", delta));
 			pgno = NODEPGNO(node);
 			mdb_node_del(mc, 0);
 			return mdb_page_split(mc, key, NULL, pgno, MDB_SPLIT_REPLACE);
 		}
 
 		numkeys = NUMKEYS(mp);
 		for (i = 0; i < numkeys; i++) {
 			if (mp->mp_ptrs[i] <= ptr)
 				mp->mp_ptrs[i] -= delta;
 		}
 
 		base = (char *)mp + mp->mp_upper + PAGEBASE;
 		len = ptr - mp->mp_upper + NODESIZE;
 		memmove(base - delta, base, len);
 		mp->mp_upper -= delta;
 
 		node = NODEPTR(mp, indx);
 	}
 
 	/* But even if no shift was needed, update ksize */
 	if (node->mn_ksize != key->mv_size)
 		node->mn_ksize = key->mv_size;
 
 	if (key->mv_size)
 		memcpy(NODEKEY(node), key->mv_data, key->mv_size);
 
 	return MDB_SUCCESS;
 }
 
 static void
 mdb_cursor_copy(const MDB_cursor *csrc, MDB_cursor *cdst);
 
 /** Perform \b act while tracking temporary cursor \b mn */
 #define WITH_CURSOR_TRACKING(mn, act) do { \
 	MDB_cursor dummy, *tracked, **tp = &(mn).mc_txn->mt_cursors[mn.mc_dbi]; \
 	if ((mn).mc_flags & C_SUB) { \
 		dummy.mc_flags =  C_INITIALIZED; \
 		dummy.mc_xcursor = (MDB_xcursor *)&(mn);	\
 		tracked = &dummy; \
 	} else { \
 		tracked = &(mn); \
 	} \
 	tracked->mc_next = *tp; \
 	*tp = tracked; \
 	{ act; } \
 	*tp = tracked->mc_next; \
 } while (0)
 
 /** Move a node from csrc to cdst.
  */
 static int
 mdb_node_move(MDB_cursor *csrc, MDB_cursor *cdst, int fromleft)
 {
 	MDB_node		*srcnode;
 	MDB_val		 key, data;
 	pgno_t	srcpg;
 	MDB_cursor mn;
 	int			 rc;
 	unsigned short flags;
 
 	DKBUF;
 
 	/* Mark src and dst as dirty. */
 	if ((rc = mdb_page_touch(csrc)) ||
 	    (rc = mdb_page_touch(cdst)))
 		return rc;
 
 	if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
 		key.mv_size = csrc->mc_db->md_pad;
 		key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top], key.mv_size);
 		data.mv_size = 0;
 		data.mv_data = NULL;
 		srcpg = 0;
 		flags = 0;
 	} else {
 		srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], csrc->mc_ki[csrc->mc_top]);
 		mdb_cassert(csrc, !((size_t)srcnode & 1));
 		srcpg = NODEPGNO(srcnode);
 		flags = srcnode->mn_flags;
 		if (csrc->mc_ki[csrc->mc_top] == 0 && IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
 			unsigned int snum = csrc->mc_snum;
 			MDB_node *s2;
 			/* must find the lowest key below src */
 			rc = mdb_page_search_lowest(csrc);
 			if (rc)
 				return rc;
 			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
 				key.mv_size = csrc->mc_db->md_pad;
 				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
 			} else {
 				s2 = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
 				key.mv_size = NODEKSZ(s2);
 				key.mv_data = NODEKEY(s2);
 			}
 			csrc->mc_snum = snum--;
 			csrc->mc_top = snum;
 		} else {
 			key.mv_size = NODEKSZ(srcnode);
 			key.mv_data = NODEKEY(srcnode);
 		}
 		data.mv_size = NODEDSZ(srcnode);
 		data.mv_data = NODEDATA(srcnode);
 	}
 	mn.mc_xcursor = NULL;
 	if (IS_BRANCH(cdst->mc_pg[cdst->mc_top]) && cdst->mc_ki[cdst->mc_top] == 0) {
 		unsigned int snum = cdst->mc_snum;
 		MDB_node *s2;
 		MDB_val bkey;
 		/* must find the lowest key below dst */
 		mdb_cursor_copy(cdst, &mn);
 		rc = mdb_page_search_lowest(&mn);
 		if (rc)
 			return rc;
 		if (IS_LEAF2(mn.mc_pg[mn.mc_top])) {
 			bkey.mv_size = mn.mc_db->md_pad;
 			bkey.mv_data = LEAF2KEY(mn.mc_pg[mn.mc_top], 0, bkey.mv_size);
 		} else {
 			s2 = NODEPTR(mn.mc_pg[mn.mc_top], 0);
 			bkey.mv_size = NODEKSZ(s2);
 			bkey.mv_data = NODEKEY(s2);
 		}
 		mn.mc_snum = snum--;
 		mn.mc_top = snum;
 		mn.mc_ki[snum] = 0;
 		rc = mdb_update_key(&mn, &bkey);
 		if (rc)
 			return rc;
 	}
 
 	DPRINTF(("moving %s node %u [%s] on page %"Z"u to node %u on page %"Z"u",
 	    IS_LEAF(csrc->mc_pg[csrc->mc_top]) ? "leaf" : "branch",
 	    csrc->mc_ki[csrc->mc_top],
 		DKEY(&key),
 	    csrc->mc_pg[csrc->mc_top]->mp_pgno,
 	    cdst->mc_ki[cdst->mc_top], cdst->mc_pg[cdst->mc_top]->mp_pgno));
 
 	/* Add the node to the destination page.
 	 */
 	rc = mdb_node_add(cdst, cdst->mc_ki[cdst->mc_top], &key, &data, srcpg, flags);
 	if (rc != MDB_SUCCESS)
 		return rc;
 
 	/* Delete the node from the source page.
 	 */
 	mdb_node_del(csrc, key.mv_size);
 
 	{
 		/* Adjust other cursors pointing to mp */
 		MDB_cursor *m2, *m3;
 		MDB_dbi dbi = csrc->mc_dbi;
 		MDB_page *mpd, *mps;
 
 		mps = csrc->mc_pg[csrc->mc_top];
 		/* If we're adding on the left, bump others up */
 		if (fromleft) {
 			mpd = cdst->mc_pg[csrc->mc_top];
 			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 				if (csrc->mc_flags & C_SUB)
 					m3 = &m2->mc_xcursor->mx_cursor;
 				else
 					m3 = m2;
 				if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
 					continue;
 				if (m3 != cdst &&
 					m3->mc_pg[csrc->mc_top] == mpd &&
 					m3->mc_ki[csrc->mc_top] >= cdst->mc_ki[csrc->mc_top]) {
 					m3->mc_ki[csrc->mc_top]++;
 				}
 				if (m3 !=csrc &&
 					m3->mc_pg[csrc->mc_top] == mps &&
 					m3->mc_ki[csrc->mc_top] == csrc->mc_ki[csrc->mc_top]) {
 					m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
 					m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
 					m3->mc_ki[csrc->mc_top-1]++;
 				}
 				if (IS_LEAF(mps))
 					XCURSOR_REFRESH(m3, csrc->mc_top, m3->mc_pg[csrc->mc_top]);
 			}
 		} else
 		/* Adding on the right, bump others down */
 		{
 			for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 				if (csrc->mc_flags & C_SUB)
 					m3 = &m2->mc_xcursor->mx_cursor;
 				else
 					m3 = m2;
 				if (m3 == csrc) continue;
 				if (!(m3->mc_flags & C_INITIALIZED) || m3->mc_top < csrc->mc_top)
 					continue;
 				if (m3->mc_pg[csrc->mc_top] == mps) {
 					if (!m3->mc_ki[csrc->mc_top]) {
 						m3->mc_pg[csrc->mc_top] = cdst->mc_pg[cdst->mc_top];
 						m3->mc_ki[csrc->mc_top] = cdst->mc_ki[cdst->mc_top];
 						m3->mc_ki[csrc->mc_top-1]--;
 					} else {
 						m3->mc_ki[csrc->mc_top]--;
 					}
 					if (IS_LEAF(mps))
 						XCURSOR_REFRESH(m3, csrc->mc_top, m3->mc_pg[csrc->mc_top]);
 				}
 			}
 		}
 	}
 
 	/* Update the parent separators.
 	 */
 	if (csrc->mc_ki[csrc->mc_top] == 0) {
 		if (csrc->mc_ki[csrc->mc_top-1] != 0) {
 			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
 				key.mv_data = LEAF2KEY(csrc->mc_pg[csrc->mc_top], 0, key.mv_size);
 			} else {
 				srcnode = NODEPTR(csrc->mc_pg[csrc->mc_top], 0);
 				key.mv_size = NODEKSZ(srcnode);
 				key.mv_data = NODEKEY(srcnode);
 			}
 			DPRINTF(("update separator for source page %"Z"u to [%s]",
 				csrc->mc_pg[csrc->mc_top]->mp_pgno, DKEY(&key)));
 			mdb_cursor_copy(csrc, &mn);
 			mn.mc_snum--;
 			mn.mc_top--;
 			/* We want mdb_rebalance to find mn when doing fixups */
 			WITH_CURSOR_TRACKING(mn,
 				rc = mdb_update_key(&mn, &key));
 			if (rc)
 				return rc;
 		}
 		if (IS_BRANCH(csrc->mc_pg[csrc->mc_top])) {
 			MDB_val	 nullkey;
 			indx_t	ix = csrc->mc_ki[csrc->mc_top];
 			nullkey.mv_size = 0;
 			csrc->mc_ki[csrc->mc_top] = 0;
 			rc = mdb_update_key(csrc, &nullkey);
 			csrc->mc_ki[csrc->mc_top] = ix;
 			mdb_cassert(csrc, rc == MDB_SUCCESS);
 		}
 	}
 
 	if (cdst->mc_ki[cdst->mc_top] == 0) {
 		if (cdst->mc_ki[cdst->mc_top-1] != 0) {
 			if (IS_LEAF2(csrc->mc_pg[csrc->mc_top])) {
 				key.mv_data = LEAF2KEY(cdst->mc_pg[cdst->mc_top], 0, key.mv_size);
 			} else {
 				srcnode = NODEPTR(cdst->mc_pg[cdst->mc_top], 0);
 				key.mv_size = NODEKSZ(srcnode);
 				key.mv_data = NODEKEY(srcnode);
 			}
 			DPRINTF(("update separator for destination page %"Z"u to [%s]",
 				cdst->mc_pg[cdst->mc_top]->mp_pgno, DKEY(&key)));
 			mdb_cursor_copy(cdst, &mn);
 			mn.mc_snum--;
 			mn.mc_top--;
 			/* We want mdb_rebalance to find mn when doing fixups */
 			WITH_CURSOR_TRACKING(mn,
 				rc = mdb_update_key(&mn, &key));
 			if (rc)
 				return rc;
 		}
 		if (IS_BRANCH(cdst->mc_pg[cdst->mc_top])) {
 			MDB_val	 nullkey;
 			indx_t	ix = cdst->mc_ki[cdst->mc_top];
 			nullkey.mv_size = 0;
 			cdst->mc_ki[cdst->mc_top] = 0;
 			rc = mdb_update_key(cdst, &nullkey);
 			cdst->mc_ki[cdst->mc_top] = ix;
 			mdb_cassert(cdst, rc == MDB_SUCCESS);
 		}
 	}
 
 	return MDB_SUCCESS;
 }
 
 /** Merge one page into another.
  *  The nodes from the page pointed to by \b csrc will
  *	be copied to the page pointed to by \b cdst and then
  *	the \b csrc page will be freed.
  * @param[in] csrc Cursor pointing to the source page.
  * @param[in] cdst Cursor pointing to the destination page.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_merge(MDB_cursor *csrc, MDB_cursor *cdst)
 {
 	MDB_page	*psrc, *pdst;
 	MDB_node	*srcnode;
 	MDB_val		 key, data;
 	unsigned	 nkeys;
 	int			 rc;
 	indx_t		 i, j;
 
 	psrc = csrc->mc_pg[csrc->mc_top];
 	pdst = cdst->mc_pg[cdst->mc_top];
 
 	DPRINTF(("merging page %"Z"u into %"Z"u", psrc->mp_pgno, pdst->mp_pgno));
 
 	mdb_cassert(csrc, csrc->mc_snum > 1);	/* can't merge root page */
 	mdb_cassert(csrc, cdst->mc_snum > 1);
 
 	/* Mark dst as dirty. */
 	if ((rc = mdb_page_touch(cdst)))
 		return rc;
 
 	/* get dst page again now that we've touched it. */
 	pdst = cdst->mc_pg[cdst->mc_top];
 
 	/* Move all nodes from src to dst.
 	 */
 	j = nkeys = NUMKEYS(pdst);
 	if (IS_LEAF2(psrc)) {
 		key.mv_size = csrc->mc_db->md_pad;
 		key.mv_data = METADATA(psrc);
 		for (i = 0; i < NUMKEYS(psrc); i++, j++) {
 			rc = mdb_node_add(cdst, j, &key, NULL, 0, 0);
 			if (rc != MDB_SUCCESS)
 				return rc;
 			key.mv_data = (char *)key.mv_data + key.mv_size;
 		}
 	} else {
 		for (i = 0; i < NUMKEYS(psrc); i++, j++) {
 			srcnode = NODEPTR(psrc, i);
 			if (i == 0 && IS_BRANCH(psrc)) {
 				MDB_cursor mn;
 				MDB_node *s2;
 				mdb_cursor_copy(csrc, &mn);
 				mn.mc_xcursor = NULL;
 				/* must find the lowest key below src */
 				rc = mdb_page_search_lowest(&mn);
 				if (rc)
 					return rc;
 				if (IS_LEAF2(mn.mc_pg[mn.mc_top])) {
 					key.mv_size = mn.mc_db->md_pad;
 					key.mv_data = LEAF2KEY(mn.mc_pg[mn.mc_top], 0, key.mv_size);
 				} else {
 					s2 = NODEPTR(mn.mc_pg[mn.mc_top], 0);
 					key.mv_size = NODEKSZ(s2);
 					key.mv_data = NODEKEY(s2);
 				}
 			} else {
 				key.mv_size = srcnode->mn_ksize;
 				key.mv_data = NODEKEY(srcnode);
 			}
 
 			data.mv_size = NODEDSZ(srcnode);
 			data.mv_data = NODEDATA(srcnode);
 			rc = mdb_node_add(cdst, j, &key, &data, NODEPGNO(srcnode), srcnode->mn_flags);
 			if (rc != MDB_SUCCESS)
 				return rc;
 		}
 	}
 
 	DPRINTF(("dst page %"Z"u now has %u keys (%.1f%% filled)",
 	    pdst->mp_pgno, NUMKEYS(pdst),
 		(float)PAGEFILL(cdst->mc_txn->mt_env, pdst) / 10));
 
 	/* Unlink the src page from parent and add to free list.
 	 */
 	csrc->mc_top--;
 	mdb_node_del(csrc, 0);
 	if (csrc->mc_ki[csrc->mc_top] == 0) {
 		key.mv_size = 0;
 		rc = mdb_update_key(csrc, &key);
 		if (rc) {
 			csrc->mc_top++;
 			return rc;
 		}
 	}
 	csrc->mc_top++;
 
 	psrc = csrc->mc_pg[csrc->mc_top];
 	/* If not operating on FreeDB, allow this page to be reused
 	 * in this txn. Otherwise just add to free list.
 	 */
 	rc = mdb_page_loose(csrc, psrc);
 	if (rc)
 		return rc;
 	if (IS_LEAF(psrc))
 		csrc->mc_db->md_leaf_pages--;
 	else
 		csrc->mc_db->md_branch_pages--;
 	{
 		/* Adjust other cursors pointing to mp */
 		MDB_cursor *m2, *m3;
 		MDB_dbi dbi = csrc->mc_dbi;
 		unsigned int top = csrc->mc_top;
 
 		for (m2 = csrc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 			if (csrc->mc_flags & C_SUB)
 				m3 = &m2->mc_xcursor->mx_cursor;
 			else
 				m3 = m2;
 			if (m3 == csrc) continue;
 			if (m3->mc_snum < csrc->mc_snum) continue;
 			if (m3->mc_pg[top] == psrc) {
 				m3->mc_pg[top] = pdst;
 				m3->mc_ki[top] += nkeys;
 				m3->mc_ki[top-1] = cdst->mc_ki[top-1];
 			} else if (m3->mc_pg[top-1] == csrc->mc_pg[top-1] &&
 				m3->mc_ki[top-1] > csrc->mc_ki[top-1]) {
 				m3->mc_ki[top-1]--;
 			}
 			if (IS_LEAF(psrc))
 				XCURSOR_REFRESH(m3, top, m3->mc_pg[top]);
 		}
 	}
 	{
 		unsigned int snum = cdst->mc_snum;
 		uint16_t depth = cdst->mc_db->md_depth;
 		mdb_cursor_pop(cdst);
 		rc = mdb_rebalance(cdst);
 		/* Did the tree height change? */
 		if (depth != cdst->mc_db->md_depth)
 			snum += cdst->mc_db->md_depth - depth;
 		cdst->mc_snum = snum;
 		cdst->mc_top = snum-1;
 	}
 	return rc;
 }
 
 /** Copy the contents of a cursor.
  * @param[in] csrc The cursor to copy from.
  * @param[out] cdst The cursor to copy to.
  */
 static void
 mdb_cursor_copy(const MDB_cursor *csrc, MDB_cursor *cdst)
 {
 	unsigned int i;
 
 	cdst->mc_txn = csrc->mc_txn;
 	cdst->mc_dbi = csrc->mc_dbi;
 	cdst->mc_db  = csrc->mc_db;
 	cdst->mc_dbx = csrc->mc_dbx;
 	cdst->mc_snum = csrc->mc_snum;
 	cdst->mc_top = csrc->mc_top;
 	cdst->mc_flags = csrc->mc_flags;
 
 	for (i=0; i<csrc->mc_snum; i++) {
 		cdst->mc_pg[i] = csrc->mc_pg[i];
 		cdst->mc_ki[i] = csrc->mc_ki[i];
 	}
 }
 
 /** Rebalance the tree after a delete operation.
  * @param[in] mc Cursor pointing to the page where rebalancing
  * should begin.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_rebalance(MDB_cursor *mc)
 {
 	MDB_node	*node;
 	int rc, fromleft;
 	unsigned int ptop, minkeys, thresh;
 	MDB_cursor	mn;
 	indx_t oldki;
 
 	if (IS_BRANCH(mc->mc_pg[mc->mc_top])) {
 		minkeys = 2;
 		thresh = 1;
 	} else {
 		minkeys = 1;
 		thresh = FILL_THRESHOLD;
 	}
 	DPRINTF(("rebalancing %s page %"Z"u (has %u keys, %.1f%% full)",
 	    IS_LEAF(mc->mc_pg[mc->mc_top]) ? "leaf" : "branch",
 	    mdb_dbg_pgno(mc->mc_pg[mc->mc_top]), NUMKEYS(mc->mc_pg[mc->mc_top]),
 		(float)PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) / 10));
 
 	if (PAGEFILL(mc->mc_txn->mt_env, mc->mc_pg[mc->mc_top]) >= thresh &&
 		NUMKEYS(mc->mc_pg[mc->mc_top]) >= minkeys) {
 		DPRINTF(("no need to rebalance page %"Z"u, above fill threshold",
 		    mdb_dbg_pgno(mc->mc_pg[mc->mc_top])));
 		return MDB_SUCCESS;
 	}
 
 	if (mc->mc_snum < 2) {
 		MDB_page *mp = mc->mc_pg[0];
 		if (IS_SUBP(mp)) {
 			DPUTS("Can't rebalance a subpage, ignoring");
 			return MDB_SUCCESS;
 		}
 		if (NUMKEYS(mp) == 0) {
 			DPUTS("tree is completely empty");
 			mc->mc_db->md_root = P_INVALID;
 			mc->mc_db->md_depth = 0;
 			mc->mc_db->md_leaf_pages = 0;
 			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
 			if (rc)
 				return rc;
 			/* Adjust cursors pointing to mp */
 			mc->mc_snum = 0;
 			mc->mc_top = 0;
 			mc->mc_flags &= ~C_INITIALIZED;
 			{
 				MDB_cursor *m2, *m3;
 				MDB_dbi dbi = mc->mc_dbi;
 
 				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 					if (mc->mc_flags & C_SUB)
 						m3 = &m2->mc_xcursor->mx_cursor;
 					else
 						m3 = m2;
 					if (!(m3->mc_flags & C_INITIALIZED) || (m3->mc_snum < mc->mc_snum))
 						continue;
 					if (m3->mc_pg[0] == mp) {
 						m3->mc_snum = 0;
 						m3->mc_top = 0;
 						m3->mc_flags &= ~C_INITIALIZED;
 					}
 				}
 			}
 		} else if (IS_BRANCH(mp) && NUMKEYS(mp) == 1) {
 			int i;
 			DPUTS("collapsing root page!");
 			rc = mdb_midl_append(&mc->mc_txn->mt_free_pgs, mp->mp_pgno);
 			if (rc)
 				return rc;
 			mc->mc_db->md_root = NODEPGNO(NODEPTR(mp, 0));
 			rc = mdb_page_get(mc, mc->mc_db->md_root, &mc->mc_pg[0], NULL);
 			if (rc)
 				return rc;
 			mc->mc_db->md_depth--;
 			mc->mc_db->md_branch_pages--;
 			mc->mc_ki[0] = mc->mc_ki[1];
 			for (i = 1; i<mc->mc_db->md_depth; i++) {
 				mc->mc_pg[i] = mc->mc_pg[i+1];
 				mc->mc_ki[i] = mc->mc_ki[i+1];
 			}
 			{
 				/* Adjust other cursors pointing to mp */
 				MDB_cursor *m2, *m3;
 				MDB_dbi dbi = mc->mc_dbi;
 
 				for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 					if (mc->mc_flags & C_SUB)
 						m3 = &m2->mc_xcursor->mx_cursor;
 					else
 						m3 = m2;
 					if (m3 == mc) continue;
 					if (!(m3->mc_flags & C_INITIALIZED))
 						continue;
 					if (m3->mc_pg[0] == mp) {
 						for (i=0; i<mc->mc_db->md_depth; i++) {
 							m3->mc_pg[i] = m3->mc_pg[i+1];
 							m3->mc_ki[i] = m3->mc_ki[i+1];
 						}
 						m3->mc_snum--;
 						m3->mc_top--;
 					}
 				}
 			}
 		} else
 			DPUTS("root page doesn't need rebalancing");
 		return MDB_SUCCESS;
 	}
 
 	/* The parent (branch page) must have at least 2 pointers,
 	 * otherwise the tree is invalid.
 	 */
 	ptop = mc->mc_top-1;
 	mdb_cassert(mc, NUMKEYS(mc->mc_pg[ptop]) > 1);
 
 	/* Leaf page fill factor is below the threshold.
 	 * Try to move keys from left or right neighbor, or
 	 * merge with a neighbor page.
 	 */
 
 	/* Find neighbors.
 	 */
 	mdb_cursor_copy(mc, &mn);
 	mn.mc_xcursor = NULL;
 
 	oldki = mc->mc_ki[mc->mc_top];
 	if (mc->mc_ki[ptop] == 0) {
 		/* We're the leftmost leaf in our parent.
 		 */
 		DPUTS("reading right neighbor");
 		mn.mc_ki[ptop]++;
 		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
 		rc = mdb_page_get(mc, NODEPGNO(node), &mn.mc_pg[mn.mc_top], NULL);
 		if (rc)
 			return rc;
 		mn.mc_ki[mn.mc_top] = 0;
 		mc->mc_ki[mc->mc_top] = NUMKEYS(mc->mc_pg[mc->mc_top]);
 		fromleft = 0;
 	} else {
 		/* There is at least one neighbor to the left.
 		 */
 		DPUTS("reading left neighbor");
 		mn.mc_ki[ptop]--;
 		node = NODEPTR(mc->mc_pg[ptop], mn.mc_ki[ptop]);
 		rc = mdb_page_get(mc, NODEPGNO(node), &mn.mc_pg[mn.mc_top], NULL);
 		if (rc)
 			return rc;
 		mn.mc_ki[mn.mc_top] = NUMKEYS(mn.mc_pg[mn.mc_top]) - 1;
 		mc->mc_ki[mc->mc_top] = 0;
 		fromleft = 1;
 	}
 
 	DPRINTF(("found neighbor page %"Z"u (%u keys, %.1f%% full)",
 	    mn.mc_pg[mn.mc_top]->mp_pgno, NUMKEYS(mn.mc_pg[mn.mc_top]),
 		(float)PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) / 10));
 
 	/* If the neighbor page is above threshold and has enough keys,
 	 * move one key from it. Otherwise we should try to merge them.
 	 * (A branch page must never have less than 2 keys.)
 	 */
 	if (PAGEFILL(mc->mc_txn->mt_env, mn.mc_pg[mn.mc_top]) >= thresh && NUMKEYS(mn.mc_pg[mn.mc_top]) > minkeys) {
 		rc = mdb_node_move(&mn, mc, fromleft);
 		if (fromleft) {
 			/* if we inserted on left, bump position up */
 			oldki++;
 		}
 	} else {
 		if (!fromleft) {
 			rc = mdb_page_merge(&mn, mc);
 		} else {
 			oldki += NUMKEYS(mn.mc_pg[mn.mc_top]);
 			mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
 			/* We want mdb_rebalance to find mn when doing fixups */
 			WITH_CURSOR_TRACKING(mn,
 				rc = mdb_page_merge(mc, &mn));
 			mdb_cursor_copy(&mn, mc);
 		}
 		mc->mc_flags &= ~C_EOF;
 	}
 	mc->mc_ki[mc->mc_top] = oldki;
 	return rc;
 }
 
 /** Complete a delete operation started by #mdb_cursor_del(). */
 static int
 mdb_cursor_del0(MDB_cursor *mc)
 {
 	int rc;
 	MDB_page *mp;
 	indx_t ki;
 	unsigned int nkeys;
 	MDB_cursor *m2, *m3;
 	MDB_dbi dbi = mc->mc_dbi;
 
 	ki = mc->mc_ki[mc->mc_top];
 	mp = mc->mc_pg[mc->mc_top];
 	mdb_node_del(mc, mc->mc_db->md_pad);
 	mc->mc_db->md_entries--;
 	{
 		/* Adjust other cursors pointing to mp */
 		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 			m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
 			if (! (m2->mc_flags & m3->mc_flags & C_INITIALIZED))
 				continue;
 			if (m3 == mc || m3->mc_snum < mc->mc_snum)
 				continue;
 			if (m3->mc_pg[mc->mc_top] == mp) {
 				if (m3->mc_ki[mc->mc_top] == ki) {
 					m3->mc_flags |= C_DEL;
 					if (mc->mc_db->md_flags & MDB_DUPSORT) {
 						/* Sub-cursor referred into dataset which is gone */
 						m3->mc_xcursor->mx_cursor.mc_flags &= ~(C_INITIALIZED|C_EOF);
 					}
 					continue;
 				} else if (m3->mc_ki[mc->mc_top] > ki) {
 					m3->mc_ki[mc->mc_top]--;
 				}
 				XCURSOR_REFRESH(m3, mc->mc_top, mp);
 			}
 		}
 	}
 	rc = mdb_rebalance(mc);
 	if (rc)
 		goto fail;
 
 	/* DB is totally empty now, just bail out.
 	 * Other cursors adjustments were already done
 	 * by mdb_rebalance and aren't needed here.
 	 */
 	if (!mc->mc_snum) {
 		mc->mc_flags |= C_EOF;
 		return rc;
 	}
 
 	mp = mc->mc_pg[mc->mc_top];
 	nkeys = NUMKEYS(mp);
 
 	/* Adjust other cursors pointing to mp */
 	for (m2 = mc->mc_txn->mt_cursors[dbi]; !rc && m2; m2=m2->mc_next) {
 		m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
 		if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
 			continue;
 		if (m3->mc_snum < mc->mc_snum)
 			continue;
 		if (m3->mc_pg[mc->mc_top] == mp) {
 			if (m3->mc_ki[mc->mc_top] >= mc->mc_ki[mc->mc_top]) {
 			/* if m3 points past last node in page, find next sibling */
 				if (m3->mc_ki[mc->mc_top] >= nkeys) {
 					rc = mdb_cursor_sibling(m3, 1);
 					if (rc == MDB_NOTFOUND) {
 						m3->mc_flags |= C_EOF;
 						rc = MDB_SUCCESS;
 						continue;
 					}
 					if (rc)
 						goto fail;
 				}
 				if (m3->mc_xcursor && !(m3->mc_flags & C_EOF)) {
 					MDB_node *node = NODEPTR(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
 					/* If this node has dupdata, it may need to be reinited
 					 * because its data has moved.
 					 * If the xcursor was not initd it must be reinited.
 					 * Else if node points to a subDB, nothing is needed.
 					 * Else (xcursor was initd, not a subDB) needs mc_pg[0] reset.
 					 */
 					if (node->mn_flags & F_DUPDATA) {
 						if (m3->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
 							if (!(node->mn_flags & F_SUBDATA))
 								m3->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(node);
 						} else {
 							mdb_xcursor_init1(m3, node);
 							rc = mdb_cursor_first(&m3->mc_xcursor->mx_cursor, NULL, NULL);
 							if (rc)
 								goto fail;
 						}
 					}
 					m3->mc_xcursor->mx_cursor.mc_flags |= C_DEL;
 				}
 			}
 		}
 	}
 	mc->mc_flags |= C_DEL;
 
 fail:
 	if (rc)
 		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 int
 mdb_del(MDB_txn *txn, MDB_dbi dbi,
     MDB_val *key, MDB_val *data)
 {
 	if (!key || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	if (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
 		return (txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
 
 	if (!F_ISSET(txn->mt_dbs[dbi].md_flags, MDB_DUPSORT)) {
 		/* must ignore any data */
 		data = NULL;
 	}
 
 	return mdb_del0(txn, dbi, key, data, 0);
 }
 
 static int
 mdb_del0(MDB_txn *txn, MDB_dbi dbi,
 	MDB_val *key, MDB_val *data, unsigned flags)
 {
 	MDB_cursor mc;
 	MDB_xcursor mx;
 	MDB_cursor_op op;
 	MDB_val rdata, *xdata;
 	int		 rc, exact = 0;
 	DKBUF;
 
 	DPRINTF(("====> delete db %u key [%s]", dbi, DKEY(key)));
 
 	mdb_cursor_init(&mc, txn, dbi, &mx);
 
 	if (data) {
 		op = MDB_GET_BOTH;
 		rdata = *data;
 		xdata = &rdata;
 	} else {
 		op = MDB_SET;
 		xdata = NULL;
 		flags |= MDB_NODUPDATA;
 	}
 	rc = mdb_cursor_set(&mc, key, xdata, op, &exact);
 	if (rc == 0) {
 		/* let mdb_page_split know about this cursor if needed:
 		 * delete will trigger a rebalance; if it needs to move
 		 * a node from one page to another, it will have to
 		 * update the parent's separator key(s). If the new sepkey
 		 * is larger than the current one, the parent page may
 		 * run out of space, triggering a split. We need this
 		 * cursor to be consistent until the end of the rebalance.
 		 */
 		mc.mc_flags |= C_UNTRACK;
 		mc.mc_next = txn->mt_cursors[dbi];
 		txn->mt_cursors[dbi] = &mc;
 		rc = mdb_cursor_del(&mc, flags);
 		txn->mt_cursors[dbi] = mc.mc_next;
 	}
 	return rc;
 }
 
 /** Split a page and insert a new node.
  * Set #MDB_TXN_ERROR on failure.
  * @param[in,out] mc Cursor pointing to the page and desired insertion index.
  * The cursor will be updated to point to the actual page and index where
  * the node got inserted after the split.
  * @param[in] newkey The key for the newly inserted node.
  * @param[in] newdata The data for the newly inserted node.
  * @param[in] newpgno The page number, if the new node is a branch node.
  * @param[in] nflags The #NODE_ADD_FLAGS for the new node.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata, pgno_t newpgno,
 	unsigned int nflags)
 {
 	unsigned int flags;
 	int		 rc = MDB_SUCCESS, new_root = 0, did_split = 0;
 	indx_t		 newindx;
 	pgno_t		 pgno = 0;
 	int	 i, j, split_indx, nkeys, pmax;
 	MDB_env 	*env = mc->mc_txn->mt_env;
 	MDB_node	*node;
 	MDB_val	 sepkey, rkey, xdata, *rdata = &xdata;
 	MDB_page	*copy = NULL;
 	MDB_page	*mp, *rp, *pp;
 	int ptop;
 	MDB_cursor	mn;
 	DKBUF;
 
 	mp = mc->mc_pg[mc->mc_top];
 	newindx = mc->mc_ki[mc->mc_top];
 	nkeys = NUMKEYS(mp);
 
 	DPRINTF(("-----> splitting %s page %"Z"u and adding [%s] at index %i/%i",
 	    IS_LEAF(mp) ? "leaf" : "branch", mp->mp_pgno,
 	    DKEY(newkey), mc->mc_ki[mc->mc_top], nkeys));
 
 	/* Create a right sibling. */
 	if ((rc = mdb_page_new(mc, mp->mp_flags, 1, &rp)))
 		return rc;
 	rp->mp_pad = mp->mp_pad;
 	DPRINTF(("new right sibling: page %"Z"u", rp->mp_pgno));
 
 	/* Usually when splitting the root page, the cursor
 	 * height is 1. But when called from mdb_update_key,
 	 * the cursor height may be greater because it walks
 	 * up the stack while finding the branch slot to update.
 	 */
 	if (mc->mc_top < 1) {
 		if ((rc = mdb_page_new(mc, P_BRANCH, 1, &pp)))
 			goto done;
 		/* shift current top to make room for new parent */
 		for (i=mc->mc_snum; i>0; i--) {
 			mc->mc_pg[i] = mc->mc_pg[i-1];
 			mc->mc_ki[i] = mc->mc_ki[i-1];
 		}
 		mc->mc_pg[0] = pp;
 		mc->mc_ki[0] = 0;
 		mc->mc_db->md_root = pp->mp_pgno;
 		DPRINTF(("root split! new root = %"Z"u", pp->mp_pgno));
 		new_root = mc->mc_db->md_depth++;
 
 		/* Add left (implicit) pointer. */
 		if ((rc = mdb_node_add(mc, 0, NULL, NULL, mp->mp_pgno, 0)) != MDB_SUCCESS) {
 			/* undo the pre-push */
 			mc->mc_pg[0] = mc->mc_pg[1];
 			mc->mc_ki[0] = mc->mc_ki[1];
 			mc->mc_db->md_root = mp->mp_pgno;
 			mc->mc_db->md_depth--;
 			goto done;
 		}
 		mc->mc_snum++;
 		mc->mc_top++;
 		ptop = 0;
 	} else {
 		ptop = mc->mc_top-1;
 		DPRINTF(("parent branch page is %"Z"u", mc->mc_pg[ptop]->mp_pgno));
 	}
 
 	mdb_cursor_copy(mc, &mn);
 	mn.mc_xcursor = NULL;
 	mn.mc_pg[mn.mc_top] = rp;
 	mn.mc_ki[ptop] = mc->mc_ki[ptop]+1;
 
 	if (nflags & MDB_APPEND) {
 		mn.mc_ki[mn.mc_top] = 0;
 		sepkey = *newkey;
 		split_indx = newindx;
 		nkeys = 0;
 	} else {
 
 		split_indx = (nkeys+1) / 2;
 
 		if (IS_LEAF2(rp)) {
 			char *split, *ins;
 			int x;
 			unsigned int lsize, rsize, ksize;
 			/* Move half of the keys to the right sibling */
 			x = mc->mc_ki[mc->mc_top] - split_indx;
 			ksize = mc->mc_db->md_pad;
 			split = LEAF2KEY(mp, split_indx, ksize);
 			rsize = (nkeys - split_indx) * ksize;
 			lsize = (nkeys - split_indx) * sizeof(indx_t);
 			mp->mp_lower -= lsize;
 			rp->mp_lower += lsize;
 			mp->mp_upper += rsize - lsize;
 			rp->mp_upper -= rsize - lsize;
 			sepkey.mv_size = ksize;
 			if (newindx == split_indx) {
 				sepkey.mv_data = newkey->mv_data;
 			} else {
 				sepkey.mv_data = split;
 			}
 			if (x<0) {
 				ins = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], ksize);
 				memcpy(rp->mp_ptrs, split, rsize);
 				sepkey.mv_data = rp->mp_ptrs;
 				memmove(ins+ksize, ins, (split_indx - mc->mc_ki[mc->mc_top]) * ksize);
 				memcpy(ins, newkey->mv_data, ksize);
 				mp->mp_lower += sizeof(indx_t);
 				mp->mp_upper -= ksize - sizeof(indx_t);
 			} else {
 				if (x)
 					memcpy(rp->mp_ptrs, split, x * ksize);
 				ins = LEAF2KEY(rp, x, ksize);
 				memcpy(ins, newkey->mv_data, ksize);
 				memcpy(ins+ksize, split + x * ksize, rsize - x * ksize);
 				rp->mp_lower += sizeof(indx_t);
 				rp->mp_upper -= ksize - sizeof(indx_t);
 				mc->mc_ki[mc->mc_top] = x;
 			}
 		} else {
 			int psize, nsize, k, keythresh;
 
 			/* Maximum free space in an empty page */
 			pmax = env->me_psize - PAGEHDRSZ;
 			/* Threshold number of keys considered "small" */
 			keythresh = env->me_psize >> 7;
 
 			if (IS_LEAF(mp))
 				nsize = mdb_leaf_size(env, newkey, newdata);
 			else
 				nsize = mdb_branch_size(env, newkey);
 			nsize = EVEN(nsize);
 
 			/* grab a page to hold a temporary copy */
 			copy = mdb_page_malloc(mc->mc_txn, 1);
 			if (copy == NULL) {
 				rc = ENOMEM;
 				goto done;
 			}
 			copy->mp_pgno  = mp->mp_pgno;
 			copy->mp_flags = mp->mp_flags;
 			copy->mp_lower = (PAGEHDRSZ-PAGEBASE);
 			copy->mp_upper = env->me_psize - PAGEBASE;
 
 			/* prepare to insert */
 			for (i=0, j=0; i<nkeys; i++) {
 				if (i == newindx) {
 					copy->mp_ptrs[j++] = 0;
 				}
 				copy->mp_ptrs[j++] = mp->mp_ptrs[i];
 			}
 
 			/* When items are relatively large the split point needs
 			 * to be checked, because being off-by-one will make the
 			 * difference between success or failure in mdb_node_add.
 			 *
 			 * It's also relevant if a page happens to be laid out
 			 * such that one half of its nodes are all "small" and
 			 * the other half of its nodes are "large." If the new
 			 * item is also "large" and falls on the half with
 			 * "large" nodes, it also may not fit.
 			 *
 			 * As a final tweak, if the new item goes on the last
 			 * spot on the page (and thus, onto the new page), bias
 			 * the split so the new page is emptier than the old page.
 			 * This yields better packing during sequential inserts.
 			 */
 			if (nkeys < keythresh || nsize > pmax/16 || newindx >= nkeys) {
 				/* Find split point */
 				psize = 0;
 				if (newindx <= split_indx || newindx >= nkeys) {
 					i = 0; j = 1;
 					k = newindx >= nkeys ? nkeys : split_indx+1+IS_LEAF(mp);
 				} else {
 					i = nkeys; j = -1;
 					k = split_indx-1;
 				}
 				for (; i!=k; i+=j) {
 					if (i == newindx) {
 						psize += nsize;
 						node = NULL;
 					} else {
 						node = (MDB_node *)((char *)mp + copy->mp_ptrs[i] + PAGEBASE);
 						psize += NODESIZE + NODEKSZ(node) + sizeof(indx_t);
 						if (IS_LEAF(mp)) {
 							if (F_ISSET(node->mn_flags, F_BIGDATA))
 								psize += sizeof(pgno_t);
 							else
 								psize += NODEDSZ(node);
 						}
 						psize = EVEN(psize);
 					}
 					if (psize > pmax || i == k-j) {
 						split_indx = i + (j<0);
 						break;
 					}
 				}
 			}
 			if (split_indx == newindx) {
 				sepkey.mv_size = newkey->mv_size;
 				sepkey.mv_data = newkey->mv_data;
 			} else {
 				node = (MDB_node *)((char *)mp + copy->mp_ptrs[split_indx] + PAGEBASE);
 				sepkey.mv_size = node->mn_ksize;
 				sepkey.mv_data = NODEKEY(node);
 			}
 		}
 	}
 
 	DPRINTF(("separator is %d [%s]", split_indx, DKEY(&sepkey)));
 
 	/* Copy separator key to the parent.
 	 */
 	if (SIZELEFT(mn.mc_pg[ptop]) < mdb_branch_size(env, &sepkey)) {
 		int snum = mc->mc_snum;
 		mn.mc_snum--;
 		mn.mc_top--;
 		did_split = 1;
 		/* We want other splits to find mn when doing fixups */
 		WITH_CURSOR_TRACKING(mn,
 			rc = mdb_page_split(&mn, &sepkey, NULL, rp->mp_pgno, 0));
 		if (rc)
 			goto done;
 
 		/* root split? */
 		if (mc->mc_snum > snum) {
 			ptop++;
 		}
 		/* Right page might now have changed parent.
 		 * Check if left page also changed parent.
 		 */
 		if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
 		    mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
 			for (i=0; i<ptop; i++) {
 				mc->mc_pg[i] = mn.mc_pg[i];
 				mc->mc_ki[i] = mn.mc_ki[i];
 			}
 			mc->mc_pg[ptop] = mn.mc_pg[ptop];
 			if (mn.mc_ki[ptop]) {
 				mc->mc_ki[ptop] = mn.mc_ki[ptop] - 1;
 			} else {
 				/* find right page's left sibling */
 				mc->mc_ki[ptop] = mn.mc_ki[ptop];
 				mdb_cursor_sibling(mc, 0);
 			}
 		}
 	} else {
 		mn.mc_top--;
 		rc = mdb_node_add(&mn, mn.mc_ki[ptop], &sepkey, NULL, rp->mp_pgno, 0);
 		mn.mc_top++;
 	}
 	if (rc != MDB_SUCCESS) {
 		goto done;
 	}
 	if (nflags & MDB_APPEND) {
 		mc->mc_pg[mc->mc_top] = rp;
 		mc->mc_ki[mc->mc_top] = 0;
 		rc = mdb_node_add(mc, 0, newkey, newdata, newpgno, nflags);
 		if (rc)
 			goto done;
 		for (i=0; i<mc->mc_top; i++)
 			mc->mc_ki[i] = mn.mc_ki[i];
 	} else if (!IS_LEAF2(mp)) {
 		/* Move nodes */
 		mc->mc_pg[mc->mc_top] = rp;
 		i = split_indx;
 		j = 0;
 		do {
 			if (i == newindx) {
 				rkey.mv_data = newkey->mv_data;
 				rkey.mv_size = newkey->mv_size;
 				if (IS_LEAF(mp)) {
 					rdata = newdata;
 				} else
 					pgno = newpgno;
 				flags = nflags;
 				/* Update index for the new key. */
 				mc->mc_ki[mc->mc_top] = j;
 			} else {
 				node = (MDB_node *)((char *)mp + copy->mp_ptrs[i] + PAGEBASE);
 				rkey.mv_data = NODEKEY(node);
 				rkey.mv_size = node->mn_ksize;
 				if (IS_LEAF(mp)) {
 					xdata.mv_data = NODEDATA(node);
 					xdata.mv_size = NODEDSZ(node);
 					rdata = &xdata;
 				} else
 					pgno = NODEPGNO(node);
 				flags = node->mn_flags;
 			}
 
 			if (!IS_LEAF(mp) && j == 0) {
 				/* First branch index doesn't need key data. */
 				rkey.mv_size = 0;
 			}
 
 			rc = mdb_node_add(mc, j, &rkey, rdata, pgno, flags);
 			if (rc)
 				goto done;
 			if (i == nkeys) {
 				i = 0;
 				j = 0;
 				mc->mc_pg[mc->mc_top] = copy;
 			} else {
 				i++;
 				j++;
 			}
 		} while (i != split_indx);
 
 		nkeys = NUMKEYS(copy);
 		for (i=0; i<nkeys; i++)
 			mp->mp_ptrs[i] = copy->mp_ptrs[i];
 		mp->mp_lower = copy->mp_lower;
 		mp->mp_upper = copy->mp_upper;
 		memcpy(NODEPTR(mp, nkeys-1), NODEPTR(copy, nkeys-1),
 			env->me_psize - copy->mp_upper - PAGEBASE);
 
 		/* reset back to original page */
 		if (newindx < split_indx) {
 			mc->mc_pg[mc->mc_top] = mp;
 		} else {
 			mc->mc_pg[mc->mc_top] = rp;
 			mc->mc_ki[ptop]++;
 			/* Make sure mc_ki is still valid.
 			 */
 			if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
 				mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
 				for (i=0; i<=ptop; i++) {
 					mc->mc_pg[i] = mn.mc_pg[i];
 					mc->mc_ki[i] = mn.mc_ki[i];
 				}
 			}
 		}
 		if (nflags & MDB_RESERVE) {
 			node = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 			if (!(node->mn_flags & F_BIGDATA))
 				newdata->mv_data = NODEDATA(node);
 		}
 	} else {
 		if (newindx >= split_indx) {
 			mc->mc_pg[mc->mc_top] = rp;
 			mc->mc_ki[ptop]++;
 			/* Make sure mc_ki is still valid.
 			 */
 			if (mn.mc_pg[ptop] != mc->mc_pg[ptop] &&
 				mc->mc_ki[ptop] >= NUMKEYS(mc->mc_pg[ptop])) {
 				for (i=0; i<=ptop; i++) {
 					mc->mc_pg[i] = mn.mc_pg[i];
 					mc->mc_ki[i] = mn.mc_ki[i];
 				}
 			}
 		}
 	}
 
 	{
 		/* Adjust other cursors pointing to mp */
 		MDB_cursor *m2, *m3;
 		MDB_dbi dbi = mc->mc_dbi;
 		nkeys = NUMKEYS(mp);
 
 		for (m2 = mc->mc_txn->mt_cursors[dbi]; m2; m2=m2->mc_next) {
 			if (mc->mc_flags & C_SUB)
 				m3 = &m2->mc_xcursor->mx_cursor;
 			else
 				m3 = m2;
 			if (m3 == mc)
 				continue;
 			if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
 				continue;
 			if (new_root) {
 				int k;
 				/* sub cursors may be on different DB */
 				if (m3->mc_pg[0] != mp)
 					continue;
 				/* root split */
 				for (k=new_root; k>=0; k--) {
 					m3->mc_ki[k+1] = m3->mc_ki[k];
 					m3->mc_pg[k+1] = m3->mc_pg[k];
 				}
 				if (m3->mc_ki[0] >= nkeys) {
 					m3->mc_ki[0] = 1;
 				} else {
 					m3->mc_ki[0] = 0;
 				}
 				m3->mc_pg[0] = mc->mc_pg[0];
 				m3->mc_snum++;
 				m3->mc_top++;
 			}
 			if (m3->mc_top >= mc->mc_top && m3->mc_pg[mc->mc_top] == mp) {
 				if (m3->mc_ki[mc->mc_top] >= newindx && !(nflags & MDB_SPLIT_REPLACE))
 					m3->mc_ki[mc->mc_top]++;
 				if (m3->mc_ki[mc->mc_top] >= nkeys) {
 					m3->mc_pg[mc->mc_top] = rp;
 					m3->mc_ki[mc->mc_top] -= nkeys;
 					for (i=0; i<mc->mc_top; i++) {
 						m3->mc_ki[i] = mn.mc_ki[i];
 						m3->mc_pg[i] = mn.mc_pg[i];
 					}
 				}
 			} else if (!did_split && m3->mc_top >= ptop && m3->mc_pg[ptop] == mc->mc_pg[ptop] &&
 				m3->mc_ki[ptop] >= mc->mc_ki[ptop]) {
 				m3->mc_ki[ptop]++;
 			}
 			if (IS_LEAF(mp))
 				XCURSOR_REFRESH(m3, mc->mc_top, m3->mc_pg[mc->mc_top]);
 		}
 	}
 	DPRINTF(("mp left: %d, rp left: %d", SIZELEFT(mp), SIZELEFT(rp)));
 
 done:
 	if (copy)					/* tmp page */
 		mdb_page_free(env, copy);
 	if (rc)
 		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
 }
 
 int
 mdb_put(MDB_txn *txn, MDB_dbi dbi,
     MDB_val *key, MDB_val *data, unsigned int flags)
 {
 	MDB_cursor mc;
 	MDB_xcursor mx;
 	int rc;
 
 	if (!key || !data || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	if (flags & ~(MDB_NOOVERWRITE|MDB_NODUPDATA|MDB_RESERVE|MDB_APPEND|MDB_APPENDDUP))
 		return EINVAL;
 
 	if (txn->mt_flags & (MDB_TXN_RDONLY|MDB_TXN_BLOCKED))
 		return (txn->mt_flags & MDB_TXN_RDONLY) ? EACCES : MDB_BAD_TXN;
 
 	mdb_cursor_init(&mc, txn, dbi, &mx);
 	mc.mc_next = txn->mt_cursors[dbi];
 	txn->mt_cursors[dbi] = &mc;
 	rc = mdb_cursor_put(&mc, key, data, flags);
 	txn->mt_cursors[dbi] = mc.mc_next;
 	return rc;
 }
 
 #ifndef MDB_WBUF
 #define MDB_WBUF	(1024*1024)
 #endif
 #define MDB_EOF		0x10	/**< #mdb_env_copyfd1() is done reading */
 
 	/** State needed for a double-buffering compacting copy. */
 typedef struct mdb_copy {
 	MDB_env *mc_env;
 	MDB_txn *mc_txn;
 	pthread_mutex_t mc_mutex;
 	pthread_cond_t mc_cond;	/**< Condition variable for #mc_new */
 	char *mc_wbuf[2];
 	char *mc_over[2];
 	int mc_wlen[2];
 	int mc_olen[2];
 	pgno_t mc_next_pgno;
 	HANDLE mc_fd;
 	int mc_toggle;			/**< Buffer number in provider */
 	int mc_new;				/**< (0-2 buffers to write) | (#MDB_EOF at end) */
 	/** Error code.  Never cleared if set.  Both threads can set nonzero
 	 *	to fail the copy.  Not mutex-protected, LMDB expects atomic int.
 	 */
 	volatile int mc_error;
 } mdb_copy;
 
 	/** Dedicated writer thread for compacting copy. */
 static THREAD_RET ESECT CALL_CONV
 mdb_env_copythr(void *arg)
 {
 	mdb_copy *my = arg;
 	char *ptr;
 	int toggle = 0, wsize, rc;
 #ifdef _WIN32
 	DWORD len;
 #define DO_WRITE(rc, fd, ptr, w2, len)	rc = WriteFile(fd, ptr, w2, &len, NULL)
 #else
 	int len;
 #define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
 #ifdef SIGPIPE
 	sigset_t set;
 	sigemptyset(&set);
 	sigaddset(&set, SIGPIPE);
 	if ((rc = pthread_sigmask(SIG_BLOCK, &set, NULL)) != 0)
 		my->mc_error = rc;
 #endif
 #endif
 
 	pthread_mutex_lock(&my->mc_mutex);
 	for(;;) {
 		while (!my->mc_new)
 			pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
 		if (my->mc_new == 0 + MDB_EOF) /* 0 buffers, just EOF */
 			break;
 		wsize = my->mc_wlen[toggle];
 		ptr = my->mc_wbuf[toggle];
 again:
 		rc = MDB_SUCCESS;
 		while (wsize > 0 && !my->mc_error) {
 			DO_WRITE(rc, my->mc_fd, ptr, wsize, len);
 			if (!rc) {
 				rc = ErrCode();
 #if defined(SIGPIPE) && !defined(_WIN32)
 				if (rc == EPIPE) {
 					/* Collect the pending SIGPIPE, otherwise at least OS X
 					 * gives it to the process on thread-exit (ITS#8504).
 					 */
 					int tmp;
 					sigwait(&set, &tmp);
 				}
 #endif
 				break;
 			} else if (len > 0) {
 				rc = MDB_SUCCESS;
 				ptr += len;
 				wsize -= len;
 				continue;
 			} else {
 				rc = EIO;
 				break;
 			}
 		}
 		if (rc) {
 			my->mc_error = rc;
 		}
 		/* If there's an overflow page tail, write it too */
 		if (my->mc_olen[toggle]) {
 			wsize = my->mc_olen[toggle];
 			ptr = my->mc_over[toggle];
 			my->mc_olen[toggle] = 0;
 			goto again;
 		}
 		my->mc_wlen[toggle] = 0;
 		toggle ^= 1;
 		/* Return the empty buffer to provider */
 		my->mc_new--;
 		pthread_cond_signal(&my->mc_cond);
 	}
 	pthread_mutex_unlock(&my->mc_mutex);
 	return (THREAD_RET)0;
 #undef DO_WRITE
 }
 
 	/** Give buffer and/or #MDB_EOF to writer thread, await unused buffer.
 	 *
 	 * @param[in] my control structure.
 	 * @param[in] adjust (1 to hand off 1 buffer) | (MDB_EOF when ending).
 	 */
 static int ESECT
 mdb_env_cthr_toggle(mdb_copy *my, int adjust)
 {
 	pthread_mutex_lock(&my->mc_mutex);
 	my->mc_new += adjust;
 	pthread_cond_signal(&my->mc_cond);
 	while (my->mc_new & 2)		/* both buffers in use */
 		pthread_cond_wait(&my->mc_cond, &my->mc_mutex);
 	pthread_mutex_unlock(&my->mc_mutex);
 
 	my->mc_toggle ^= (adjust & 1);
 	/* Both threads reset mc_wlen, to be safe from threading errors */
 	my->mc_wlen[my->mc_toggle] = 0;
 	return my->mc_error;
 }
 
 	/** Depth-first tree traversal for compacting copy.
 	 * @param[in] my control structure.
 	 * @param[in,out] pg database root.
 	 * @param[in] flags includes #F_DUPDATA if it is a sorted-duplicate sub-DB.
 	 */
 static int ESECT
 mdb_env_cwalk(mdb_copy *my, pgno_t *pg, int flags)
 {
 	MDB_cursor mc = {0};
 	MDB_node *ni;
 	MDB_page *mo, *mp, *leaf;
 	char *buf, *ptr;
 	int rc, toggle;
 	unsigned int i;
 
 	/* Empty DB, nothing to do */
 	if (*pg == P_INVALID)
 		return MDB_SUCCESS;
 
 	mc.mc_snum = 1;
 	mc.mc_txn = my->mc_txn;
 
 	rc = mdb_page_get(&mc, *pg, &mc.mc_pg[0], NULL);
 	if (rc)
 		return rc;
 	rc = mdb_page_search_root(&mc, NULL, MDB_PS_FIRST);
 	if (rc)
 		return rc;
 
 	/* Make cursor pages writable */
 	buf = ptr = malloc(my->mc_env->me_psize * mc.mc_snum);
 	if (buf == NULL)
 		return ENOMEM;
 
 	for (i=0; i<mc.mc_top; i++) {
 		mdb_page_copy((MDB_page *)ptr, mc.mc_pg[i], my->mc_env->me_psize);
 		mc.mc_pg[i] = (MDB_page *)ptr;
 		ptr += my->mc_env->me_psize;
 	}
 
 	/* This is writable space for a leaf page. Usually not needed. */
 	leaf = (MDB_page *)ptr;
 
 	toggle = my->mc_toggle;
 	while (mc.mc_snum > 0) {
 		unsigned n;
 		mp = mc.mc_pg[mc.mc_top];
 		n = NUMKEYS(mp);
 
 		if (IS_LEAF(mp)) {
 			if (!IS_LEAF2(mp) && !(flags & F_DUPDATA)) {
 				for (i=0; i<n; i++) {
 					ni = NODEPTR(mp, i);
 					if (ni->mn_flags & F_BIGDATA) {
 						MDB_page *omp;
 						pgno_t pg;
 
 						/* Need writable leaf */
 						if (mp != leaf) {
 							mc.mc_pg[mc.mc_top] = leaf;
 							mdb_page_copy(leaf, mp, my->mc_env->me_psize);
 							mp = leaf;
 							ni = NODEPTR(mp, i);
 						}
 
 						memcpy(&pg, NODEDATA(ni), sizeof(pg));
 						memcpy(NODEDATA(ni), &my->mc_next_pgno, sizeof(pgno_t));
 						rc = mdb_page_get(&mc, pg, &omp, NULL);
 						if (rc)
 							goto done;
 						if (my->mc_wlen[toggle] >= MDB_WBUF) {
 							rc = mdb_env_cthr_toggle(my, 1);
 							if (rc)
 								goto done;
 							toggle = my->mc_toggle;
 						}
 						mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
 						memcpy(mo, omp, my->mc_env->me_psize);
 						mo->mp_pgno = my->mc_next_pgno;
 						my->mc_next_pgno += omp->mp_pages;
 						my->mc_wlen[toggle] += my->mc_env->me_psize;
 						if (omp->mp_pages > 1) {
 							my->mc_olen[toggle] = my->mc_env->me_psize * (omp->mp_pages - 1);
 							my->mc_over[toggle] = (char *)omp + my->mc_env->me_psize;
 							rc = mdb_env_cthr_toggle(my, 1);
 							if (rc)
 								goto done;
 							toggle = my->mc_toggle;
 						}
 					} else if (ni->mn_flags & F_SUBDATA) {
 						MDB_db db;
 
 						/* Need writable leaf */
 						if (mp != leaf) {
 							mc.mc_pg[mc.mc_top] = leaf;
 							mdb_page_copy(leaf, mp, my->mc_env->me_psize);
 							mp = leaf;
 							ni = NODEPTR(mp, i);
 						}
 
 						memcpy(&db, NODEDATA(ni), sizeof(db));
 						my->mc_toggle = toggle;
 						rc = mdb_env_cwalk(my, &db.md_root, ni->mn_flags & F_DUPDATA);
 						if (rc)
 							goto done;
 						toggle = my->mc_toggle;
 						memcpy(NODEDATA(ni), &db, sizeof(db));
 					}
 				}
 			}
 		} else {
 			mc.mc_ki[mc.mc_top]++;
 			if (mc.mc_ki[mc.mc_top] < n) {
 				pgno_t pg;
 again:
 				ni = NODEPTR(mp, mc.mc_ki[mc.mc_top]);
 				pg = NODEPGNO(ni);
 				rc = mdb_page_get(&mc, pg, &mp, NULL);
 				if (rc)
 					goto done;
 				mc.mc_top++;
 				mc.mc_snum++;
 				mc.mc_ki[mc.mc_top] = 0;
 				if (IS_BRANCH(mp)) {
 					/* Whenever we advance to a sibling branch page,
 					 * we must proceed all the way down to its first leaf.
 					 */
 					mdb_page_copy(mc.mc_pg[mc.mc_top], mp, my->mc_env->me_psize);
 					goto again;
 				} else
 					mc.mc_pg[mc.mc_top] = mp;
 				continue;
 			}
 		}
 		if (my->mc_wlen[toggle] >= MDB_WBUF) {
 			rc = mdb_env_cthr_toggle(my, 1);
 			if (rc)
 				goto done;
 			toggle = my->mc_toggle;
 		}
 		mo = (MDB_page *)(my->mc_wbuf[toggle] + my->mc_wlen[toggle]);
 		mdb_page_copy(mo, mp, my->mc_env->me_psize);
 		mo->mp_pgno = my->mc_next_pgno++;
 		my->mc_wlen[toggle] += my->mc_env->me_psize;
 		if (mc.mc_top) {
 			/* Update parent if there is one */
 			ni = NODEPTR(mc.mc_pg[mc.mc_top-1], mc.mc_ki[mc.mc_top-1]);
 			SETPGNO(ni, mo->mp_pgno);
 			mdb_cursor_pop(&mc);
 		} else {
 			/* Otherwise we're done */
 			*pg = mo->mp_pgno;
 			break;
 		}
 	}
 done:
 	free(buf);
 	return rc;
 }
 
 	/** Copy environment with compaction. */
 static int ESECT
 mdb_env_copyfd1(MDB_env *env, HANDLE fd)
 {
 	MDB_meta *mm;
 	MDB_page *mp;
 	mdb_copy my = {0};
 	MDB_txn *txn = NULL;
 	pthread_t thr;
 	pgno_t root, new_root;
 	int rc = MDB_SUCCESS;
 
 #ifdef _WIN32
 	if (!(my.mc_mutex = CreateMutex(NULL, FALSE, NULL)) ||
 		!(my.mc_cond = CreateEvent(NULL, FALSE, FALSE, NULL))) {
 		rc = ErrCode();
 		goto done;
 	}
 	my.mc_wbuf[0] = _aligned_malloc(MDB_WBUF*2, env->me_os_psize);
 	if (my.mc_wbuf[0] == NULL) {
 		/* _aligned_malloc() sets errno, but we use Windows error codes */
 		rc = ERROR_NOT_ENOUGH_MEMORY;
 		goto done;
 	}
 #else
 	if ((rc = pthread_mutex_init(&my.mc_mutex, NULL)) != 0)
 		return rc;
 	if ((rc = pthread_cond_init(&my.mc_cond, NULL)) != 0)
 		goto done2;
 #ifdef HAVE_MEMALIGN
 	my.mc_wbuf[0] = memalign(env->me_os_psize, MDB_WBUF*2);
 	if (my.mc_wbuf[0] == NULL) {
 		rc = errno;
 		goto done;
 	}
 #else
 	{
 		void *p;
 		if ((rc = posix_memalign(&p, env->me_os_psize, MDB_WBUF*2)) != 0)
 			goto done;
 		my.mc_wbuf[0] = p;
 	}
 #endif
 #endif
 	memset(my.mc_wbuf[0], 0, MDB_WBUF*2);
 	my.mc_wbuf[1] = my.mc_wbuf[0] + MDB_WBUF;
 	my.mc_next_pgno = NUM_METAS;
 	my.mc_env = env;
 	my.mc_fd = fd;
 	rc = THREAD_CREATE(thr, mdb_env_copythr, &my);
 	if (rc)
 		goto done;
 
 	rc = mdb_txn_begin(env, NULL, MDB_RDONLY, &txn);
 	if (rc)
 		goto finish;
 
 	mp = (MDB_page *)my.mc_wbuf[0];
 	memset(mp, 0, NUM_METAS * env->me_psize);
 	mp->mp_pgno = 0;
 	mp->mp_flags = P_META;
 	mm = (MDB_meta *)METADATA(mp);
 	mdb_env_init_meta0(env, mm);
 	mm->mm_address = env->me_metas[0]->mm_address;
 
 	mp = (MDB_page *)(my.mc_wbuf[0] + env->me_psize);
 	mp->mp_pgno = 1;
 	mp->mp_flags = P_META;
 	*(MDB_meta *)METADATA(mp) = *mm;
 	mm = (MDB_meta *)METADATA(mp);
 
 	/* Set metapage 1 with current main DB */
 	root = new_root = txn->mt_dbs[MAIN_DBI].md_root;
 	if (root != P_INVALID) {
 		/* Count free pages + freeDB pages.  Subtract from last_pg
 		 * to find the new last_pg, which also becomes the new root.
 		 */
 		MDB_ID freecount = 0;
 		MDB_cursor mc;
 		MDB_val key, data;
 		mdb_cursor_init(&mc, txn, FREE_DBI, NULL);
 		while ((rc = mdb_cursor_get(&mc, &key, &data, MDB_NEXT)) == 0)
 			freecount += *(MDB_ID *)data.mv_data;
 		if (rc != MDB_NOTFOUND)
 			goto finish;
 		freecount += txn->mt_dbs[FREE_DBI].md_branch_pages +
 			txn->mt_dbs[FREE_DBI].md_leaf_pages +
 			txn->mt_dbs[FREE_DBI].md_overflow_pages;
 
 		new_root = txn->mt_next_pgno - 1 - freecount;
 		mm->mm_last_pg = new_root;
 		mm->mm_dbs[MAIN_DBI] = txn->mt_dbs[MAIN_DBI];
 		mm->mm_dbs[MAIN_DBI].md_root = new_root;
 	} else {
 		/* When the DB is empty, handle it specially to
 		 * fix any breakage like page leaks from ITS#8174.
 		 */
 		mm->mm_dbs[MAIN_DBI].md_flags = txn->mt_dbs[MAIN_DBI].md_flags;
 	}
 	if (root != P_INVALID || mm->mm_dbs[MAIN_DBI].md_flags) {
 		mm->mm_txnid = 1;		/* use metapage 1 */
 	}
 
 	my.mc_wlen[0] = env->me_psize * NUM_METAS;
 	my.mc_txn = txn;
 	rc = mdb_env_cwalk(&my, &root, 0);
 	if (rc == MDB_SUCCESS && root != new_root) {
 		rc = MDB_INCOMPATIBLE;	/* page leak or corrupt DB */
 	}
 
 finish:
 	if (rc)
 		my.mc_error = rc;
 	mdb_env_cthr_toggle(&my, 1 | MDB_EOF);
 	rc = THREAD_FINISH(thr);
 	mdb_txn_abort(txn);
 
 done:
 #ifdef _WIN32
 	if (my.mc_wbuf[0]) _aligned_free(my.mc_wbuf[0]);
 	if (my.mc_cond)  CloseHandle(my.mc_cond);
 	if (my.mc_mutex) CloseHandle(my.mc_mutex);
 #else
 	free(my.mc_wbuf[0]);
 	pthread_cond_destroy(&my.mc_cond);
 done2:
 	pthread_mutex_destroy(&my.mc_mutex);
 #endif
 	return rc ? rc : my.mc_error;
 }
 
 	/** Copy environment as-is. */
 static int ESECT
 mdb_env_copyfd0(MDB_env *env, HANDLE fd)
 {
 	MDB_txn *txn = NULL;
 	mdb_mutexref_t wmutex = NULL;
 	int rc;
 	size_t wsize, w3;
 	char *ptr;
 #ifdef _WIN32
 	DWORD len, w2;
 #define DO_WRITE(rc, fd, ptr, w2, len)	rc = WriteFile(fd, ptr, w2, &len, NULL)
 #else
 	ssize_t len;
 	size_t w2;
 #define DO_WRITE(rc, fd, ptr, w2, len)	len = write(fd, ptr, w2); rc = (len >= 0)
 #endif
 
 	/* Do the lock/unlock of the reader mutex before starting the
 	 * write txn.  Otherwise other read txns could block writers.
 	 */
 	rc = mdb_txn_begin(env, NULL, MDB_RDONLY, &txn);
 	if (rc)
 		return rc;
 
 	if (env->me_txns) {
 		/* We must start the actual read txn after blocking writers */
 		mdb_txn_end(txn, MDB_END_RESET_TMP);
 
 		/* Temporarily block writers until we snapshot the meta pages */
 		wmutex = env->me_wmutex;
 		if (LOCK_MUTEX(rc, env, wmutex))
 			goto leave;
 
 		rc = mdb_txn_renew0(txn);
 		if (rc) {
 			UNLOCK_MUTEX(wmutex);
 			goto leave;
 		}
 	}
 
 	wsize = env->me_psize * NUM_METAS;
 	ptr = env->me_map;
 	w2 = wsize;
 	while (w2 > 0) {
 		DO_WRITE(rc, fd, ptr, w2, len);
 		if (!rc) {
 			rc = ErrCode();
 			break;
 		} else if (len > 0) {
 			rc = MDB_SUCCESS;
 			ptr += len;
 			w2 -= len;
 			continue;
 		} else {
 			/* Non-blocking or async handles are not supported */
 			rc = EIO;
 			break;
 		}
 	}
 	if (wmutex)
 		UNLOCK_MUTEX(wmutex);
 
 	if (rc)
 		goto leave;
 
 	w3 = txn->mt_next_pgno * env->me_psize;
 	{
 		size_t fsize = 0;
 		if ((rc = mdb_fsize(env->me_fd, &fsize)))
 			goto leave;
 		if (w3 > fsize)
 			w3 = fsize;
 	}
 	wsize = w3 - wsize;
 	while (wsize > 0) {
 		if (wsize > MAX_WRITE)
 			w2 = MAX_WRITE;
 		else
 			w2 = wsize;
 		DO_WRITE(rc, fd, ptr, w2, len);
 		if (!rc) {
 			rc = ErrCode();
 			break;
 		} else if (len > 0) {
 			rc = MDB_SUCCESS;
 			ptr += len;
 			wsize -= len;
 			continue;
 		} else {
 			rc = EIO;
 			break;
 		}
 	}
 
 leave:
 	mdb_txn_abort(txn);
 	return rc;
 }
 
 int ESECT
 mdb_env_copyfd2(MDB_env *env, HANDLE fd, unsigned int flags)
 {
 	if (flags & MDB_CP_COMPACT)
 		return mdb_env_copyfd1(env, fd);
 	else
 		return mdb_env_copyfd0(env, fd);
 }
 
 int ESECT
 mdb_env_copyfd(MDB_env *env, HANDLE fd)
 {
 	return mdb_env_copyfd2(env, fd, 0);
 }
 
 int ESECT
 mdb_env_copy2(MDB_env *env, const char *path, unsigned int flags)
 {
 	int rc;
 	MDB_name fname;
 	HANDLE newfd = INVALID_HANDLE_VALUE;
 
 	rc = mdb_fname_init(path, env->me_flags | MDB_NOLOCK, &fname);
 	if (rc == MDB_SUCCESS) {
 		rc = mdb_fopen(env, &fname, MDB_O_COPY, 0666, &newfd);
 		mdb_fname_destroy(fname);
 	}
 	if (rc == MDB_SUCCESS) {
 		rc = mdb_env_copyfd2(env, newfd, flags);
 		if (close(newfd) < 0 && rc == MDB_SUCCESS)
 			rc = ErrCode();
 	}
 	return rc;
 }
 
 int ESECT
 mdb_env_copy(MDB_env *env, const char *path)
 {
 	return mdb_env_copy2(env, path, 0);
 }
 
 int ESECT
 mdb_env_set_flags(MDB_env *env, unsigned int flag, int onoff)
 {
 	if (flag & ~CHANGEABLE)
 		return EINVAL;
 	if (onoff)
 		env->me_flags |= flag;
 	else
 		env->me_flags &= ~flag;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_get_flags(MDB_env *env, unsigned int *arg)
 {
 	if (!env || !arg)
 		return EINVAL;
 
 	*arg = env->me_flags & (CHANGEABLE|CHANGELESS);
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_set_userctx(MDB_env *env, void *ctx)
 {
 	if (!env)
 		return EINVAL;
 	env->me_userctx = ctx;
 	return MDB_SUCCESS;
 }
 
 void * ESECT
 mdb_env_get_userctx(MDB_env *env)
 {
 	return env ? env->me_userctx : NULL;
 }
 
 int ESECT
 mdb_env_set_assert(MDB_env *env, MDB_assert_func *func)
 {
 	if (!env)
 		return EINVAL;
 #ifndef NDEBUG
 	env->me_assert_func = func;
 #endif
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_get_path(MDB_env *env, const char **arg)
 {
 	if (!env || !arg)
 		return EINVAL;
 
 	*arg = env->me_path;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_get_fd(MDB_env *env, mdb_filehandle_t *arg)
 {
 	if (!env || !arg)
 		return EINVAL;
 
 	*arg = env->me_fd;
 	return MDB_SUCCESS;
 }
 
 /** Common code for #mdb_stat() and #mdb_env_stat().
  * @param[in] env the environment to operate in.
  * @param[in] db the #MDB_db record containing the stats to return.
  * @param[out] arg the address of an #MDB_stat structure to receive the stats.
  * @return 0, this function always succeeds.
  */
 static int ESECT
 mdb_stat0(MDB_env *env, MDB_db *db, MDB_stat *arg)
 {
 	arg->ms_psize = env->me_psize;
 	arg->ms_depth = db->md_depth;
 	arg->ms_branch_pages = db->md_branch_pages;
 	arg->ms_leaf_pages = db->md_leaf_pages;
 	arg->ms_overflow_pages = db->md_overflow_pages;
 	arg->ms_entries = db->md_entries;
 
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_stat(MDB_env *env, MDB_stat *arg)
 {
 	MDB_meta *meta;
 
 	if (env == NULL || arg == NULL)
 		return EINVAL;
 
 	meta = mdb_env_pick_meta(env);
 
 	return mdb_stat0(env, &meta->mm_dbs[MAIN_DBI], arg);
 }
 
 int ESECT
 mdb_env_info(MDB_env *env, MDB_envinfo *arg)
 {
 	MDB_meta *meta;
 
 	if (env == NULL || arg == NULL)
 		return EINVAL;
 
 	meta = mdb_env_pick_meta(env);
 	arg->me_mapaddr = meta->mm_address;
 	arg->me_last_pgno = meta->mm_last_pg;
 	arg->me_last_txnid = meta->mm_txnid;
 
 	arg->me_mapsize = env->me_mapsize;
 	arg->me_maxreaders = env->me_maxreaders;
 	arg->me_numreaders = env->me_txns ? env->me_txns->mti_numreaders : 0;
 	return MDB_SUCCESS;
 }
 
 /** Set the default comparison functions for a database.
  * Called immediately after a database is opened to set the defaults.
  * The user can then override them with #mdb_set_compare() or
  * #mdb_set_dupsort().
  * @param[in] txn A transaction handle returned by #mdb_txn_begin()
  * @param[in] dbi A database handle returned by #mdb_dbi_open()
  */
 static void
 mdb_default_cmp(MDB_txn *txn, MDB_dbi dbi)
 {
 	uint16_t f = txn->mt_dbs[dbi].md_flags;
 
 	txn->mt_dbxs[dbi].md_cmp =
 		(f & MDB_REVERSEKEY) ? mdb_cmp_memnr :
 		(f & MDB_INTEGERKEY) ? mdb_cmp_cint  : mdb_cmp_memn;
 
 	txn->mt_dbxs[dbi].md_dcmp =
 		!(f & MDB_DUPSORT) ? 0 :
 		((f & MDB_INTEGERDUP)
 		 ? ((f & MDB_DUPFIXED)   ? mdb_cmp_int   : mdb_cmp_cint)
 		 : ((f & MDB_REVERSEDUP) ? mdb_cmp_memnr : mdb_cmp_memn));
 }
 
 int mdb_dbi_open(MDB_txn *txn, const char *name, unsigned int flags, MDB_dbi *dbi)
 {
 	MDB_val key, data;
 	MDB_dbi i;
 	MDB_cursor mc;
 	MDB_db dummy;
 	int rc, dbflag, exact;
 	unsigned int unused = 0, seq;
 	char *namedup;
 	size_t len;
 
 	if (flags & ~VALID_FLAGS)
 		return EINVAL;
 	if (txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	/* main DB? */
 	if (!name) {
 		*dbi = MAIN_DBI;
 		if (flags & PERSISTENT_FLAGS) {
 			uint16_t f2 = flags & PERSISTENT_FLAGS;
 			/* make sure flag changes get committed */
 			if ((txn->mt_dbs[MAIN_DBI].md_flags | f2) != txn->mt_dbs[MAIN_DBI].md_flags) {
 				txn->mt_dbs[MAIN_DBI].md_flags |= f2;
 				txn->mt_flags |= MDB_TXN_DIRTY;
 			}
 		}
 		mdb_default_cmp(txn, MAIN_DBI);
 		return MDB_SUCCESS;
 	}
 
 	if (txn->mt_dbxs[MAIN_DBI].md_cmp == NULL) {
 		mdb_default_cmp(txn, MAIN_DBI);
 	}
 
 	/* Is the DB already open? */
 	len = strlen(name);
 	for (i=CORE_DBS; i<txn->mt_numdbs; i++) {
 		if (!txn->mt_dbxs[i].md_name.mv_size) {
 			/* Remember this free slot */
 			if (!unused) unused = i;
 			continue;
 		}
 		if (len == txn->mt_dbxs[i].md_name.mv_size &&
 			!strncmp(name, txn->mt_dbxs[i].md_name.mv_data, len)) {
 			*dbi = i;
 			return MDB_SUCCESS;
 		}
 	}
 
 	/* If no free slot and max hit, fail */
 	if (!unused && txn->mt_numdbs >= txn->mt_env->me_maxdbs)
 		return MDB_DBS_FULL;
 
 	/* Cannot mix named databases with some mainDB flags */
 	if (txn->mt_dbs[MAIN_DBI].md_flags & (MDB_DUPSORT|MDB_INTEGERKEY))
 		return (flags & MDB_CREATE) ? MDB_INCOMPATIBLE : MDB_NOTFOUND;
 
 	/* Find the DB info */
 	dbflag = DB_NEW|DB_VALID|DB_USRVALID;
 	exact = 0;
 	key.mv_size = len;
 	key.mv_data = (void *)name;
 	mdb_cursor_init(&mc, txn, MAIN_DBI, NULL);
 	rc = mdb_cursor_set(&mc, &key, &data, MDB_SET, &exact);
 	if (rc == MDB_SUCCESS) {
 		/* make sure this is actually a DB */
 		MDB_node *node = NODEPTR(mc.mc_pg[mc.mc_top], mc.mc_ki[mc.mc_top]);
 		if ((node->mn_flags & (F_DUPDATA|F_SUBDATA)) != F_SUBDATA)
 			return MDB_INCOMPATIBLE;
 	} else {
 		if (rc != MDB_NOTFOUND || !(flags & MDB_CREATE))
 			return rc;
 		if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
 			return EACCES;
 	}
 
 	/* Done here so we cannot fail after creating a new DB */
 	if ((namedup = strdup(name)) == NULL)
 		return ENOMEM;
 
 	if (rc) {
 		/* MDB_NOTFOUND and MDB_CREATE: Create new DB */
 		data.mv_size = sizeof(MDB_db);
 		data.mv_data = &dummy;
 		memset(&dummy, 0, sizeof(dummy));
 		dummy.md_root = P_INVALID;
 		dummy.md_flags = flags & PERSISTENT_FLAGS;
 		WITH_CURSOR_TRACKING(mc,
 			rc = mdb_cursor_put(&mc, &key, &data, F_SUBDATA));
 		dbflag |= DB_DIRTY;
 	}
 
 	if (rc) {
 		free(namedup);
 	} else {
 		/* Got info, register DBI in this txn */
 		unsigned int slot = unused ? unused : txn->mt_numdbs;
 		txn->mt_dbxs[slot].md_name.mv_data = namedup;
 		txn->mt_dbxs[slot].md_name.mv_size = len;
 		txn->mt_dbxs[slot].md_rel = NULL;
 		txn->mt_dbflags[slot] = dbflag;
 		/* txn-> and env-> are the same in read txns, use
 		 * tmp variable to avoid undefined assignment
 		 */
 		seq = ++txn->mt_env->me_dbiseqs[slot];
 		txn->mt_dbiseqs[slot] = seq;
 
 		memcpy(&txn->mt_dbs[slot], data.mv_data, sizeof(MDB_db));
 		*dbi = slot;
 		mdb_default_cmp(txn, slot);
 		if (!unused) {
 			txn->mt_numdbs++;
 		}
 	}
 
 	return rc;
 }
 
 int ESECT
 mdb_stat(MDB_txn *txn, MDB_dbi dbi, MDB_stat *arg)
 {
 	if (!arg || !TXN_DBI_EXIST(txn, dbi, DB_VALID))
 		return EINVAL;
 
 	if (txn->mt_flags & MDB_TXN_BLOCKED)
 		return MDB_BAD_TXN;
 
 	if (txn->mt_dbflags[dbi] & DB_STALE) {
 		MDB_cursor mc;
 		MDB_xcursor mx;
 		/* Stale, must read the DB's root. cursor_init does it for us. */
 		mdb_cursor_init(&mc, txn, dbi, &mx);
 	}
 	return mdb_stat0(txn->mt_env, &txn->mt_dbs[dbi], arg);
 }
 
 void mdb_dbi_close(MDB_env *env, MDB_dbi dbi)
 {
 	char *ptr;
 	if (dbi < CORE_DBS || dbi >= env->me_maxdbs)
 		return;
 	ptr = env->me_dbxs[dbi].md_name.mv_data;
 	/* If there was no name, this was already closed */
 	if (ptr) {
 		env->me_dbxs[dbi].md_name.mv_data = NULL;
 		env->me_dbxs[dbi].md_name.mv_size = 0;
 		env->me_dbflags[dbi] = 0;
 		env->me_dbiseqs[dbi]++;
 		free(ptr);
 	}
 }
 
 int mdb_dbi_flags(MDB_txn *txn, MDB_dbi dbi, unsigned int *flags)
 {
 	/* We could return the flags for the FREE_DBI too but what's the point? */
 	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 	*flags = txn->mt_dbs[dbi].md_flags & PERSISTENT_FLAGS;
 	return MDB_SUCCESS;
 }
 
 /** Add all the DB's pages to the free list.
  * @param[in] mc Cursor on the DB to free.
  * @param[in] subs non-Zero to check for sub-DBs in this DB.
  * @return 0 on success, non-zero on failure.
  */
 static int
 mdb_drop0(MDB_cursor *mc, int subs)
 {
 	int rc;
 
 	rc = mdb_page_search(mc, NULL, MDB_PS_FIRST);
 	if (rc == MDB_SUCCESS) {
 		MDB_txn *txn = mc->mc_txn;
 		MDB_node *ni;
 		MDB_cursor mx;
 		unsigned int i;
 
 		/* DUPSORT sub-DBs have no ovpages/DBs. Omit scanning leaves.
 		 * This also avoids any P_LEAF2 pages, which have no nodes.
 		 * Also if the DB doesn't have sub-DBs and has no overflow
 		 * pages, omit scanning leaves.
 		 */
 		if ((mc->mc_flags & C_SUB) ||
 			(!subs && !mc->mc_db->md_overflow_pages))
 			mdb_cursor_pop(mc);
 
 		mdb_cursor_copy(mc, &mx);
 		while (mc->mc_snum > 0) {
 			MDB_page *mp = mc->mc_pg[mc->mc_top];
 			unsigned n = NUMKEYS(mp);
 			if (IS_LEAF(mp)) {
 				for (i=0; i<n; i++) {
 					ni = NODEPTR(mp, i);
 					if (ni->mn_flags & F_BIGDATA) {
 						MDB_page *omp;
 						pgno_t pg;
 						memcpy(&pg, NODEDATA(ni), sizeof(pg));
 						rc = mdb_page_get(mc, pg, &omp, NULL);
 						if (rc != 0)
 							goto done;
 						mdb_cassert(mc, IS_OVERFLOW(omp));
 						rc = mdb_midl_append_range(&txn->mt_free_pgs,
 							pg, omp->mp_pages);
 						if (rc)
 							goto done;
 						mc->mc_db->md_overflow_pages -= omp->mp_pages;
 						if (!mc->mc_db->md_overflow_pages && !subs)
 							break;
 					} else if (subs && (ni->mn_flags & F_SUBDATA)) {
 						mdb_xcursor_init1(mc, ni);
 						rc = mdb_drop0(&mc->mc_xcursor->mx_cursor, 0);
 						if (rc)
 							goto done;
 					}
 				}
 				if (!subs && !mc->mc_db->md_overflow_pages)
 					goto pop;
 			} else {
 				if ((rc = mdb_midl_need(&txn->mt_free_pgs, n)) != 0)
 					goto done;
 				for (i=0; i<n; i++) {
 					pgno_t pg;
 					ni = NODEPTR(mp, i);
 					pg = NODEPGNO(ni);
 					/* free it */
 					mdb_midl_xappend(txn->mt_free_pgs, pg);
 				}
 			}
 			if (!mc->mc_top)
 				break;
 			mc->mc_ki[mc->mc_top] = i;
 			rc = mdb_cursor_sibling(mc, 1);
 			if (rc) {
 				if (rc != MDB_NOTFOUND)
 					goto done;
 				/* no more siblings, go back to beginning
 				 * of previous level.
 				 */
 pop:
 				mdb_cursor_pop(mc);
 				mc->mc_ki[0] = 0;
 				for (i=1; i<mc->mc_snum; i++) {
 					mc->mc_ki[i] = 0;
 					mc->mc_pg[i] = mx.mc_pg[i];
 				}
 			}
 		}
 		/* free it */
 		rc = mdb_midl_append(&txn->mt_free_pgs, mc->mc_db->md_root);
 done:
 		if (rc)
 			txn->mt_flags |= MDB_TXN_ERROR;
 	} else if (rc == MDB_NOTFOUND) {
 		rc = MDB_SUCCESS;
 	}
 	mc->mc_flags &= ~C_INITIALIZED;
 	return rc;
 }
 
 int mdb_drop(MDB_txn *txn, MDB_dbi dbi, int del)
 {
 	MDB_cursor *mc, *m2;
 	int rc;
 
 	if ((unsigned)del > 1 || !TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	if (F_ISSET(txn->mt_flags, MDB_TXN_RDONLY))
 		return EACCES;
 
 	if (TXN_DBI_CHANGED(txn, dbi))
 		return MDB_BAD_DBI;
 
 	rc = mdb_cursor_open(txn, dbi, &mc);
 	if (rc)
 		return rc;
 
 	rc = mdb_drop0(mc, mc->mc_db->md_flags & MDB_DUPSORT);
 	/* Invalidate the dropped DB's cursors */
 	for (m2 = txn->mt_cursors[dbi]; m2; m2 = m2->mc_next)
 		m2->mc_flags &= ~(C_INITIALIZED|C_EOF);
 	if (rc)
 		goto leave;
 
 	/* Can't delete the main DB */
 	if (del && dbi >= CORE_DBS) {
 		rc = mdb_del0(txn, MAIN_DBI, &mc->mc_dbx->md_name, NULL, F_SUBDATA);
 		if (!rc) {
 			txn->mt_dbflags[dbi] = DB_STALE;
 			mdb_dbi_close(txn->mt_env, dbi);
 		} else {
 			txn->mt_flags |= MDB_TXN_ERROR;
 		}
 	} else {
 		/* reset the DB record, mark it dirty */
 		txn->mt_dbflags[dbi] |= DB_DIRTY;
 		txn->mt_dbs[dbi].md_depth = 0;
 		txn->mt_dbs[dbi].md_branch_pages = 0;
 		txn->mt_dbs[dbi].md_leaf_pages = 0;
 		txn->mt_dbs[dbi].md_overflow_pages = 0;
 		txn->mt_dbs[dbi].md_entries = 0;
 		txn->mt_dbs[dbi].md_root = P_INVALID;
 
 		txn->mt_flags |= MDB_TXN_DIRTY;
 	}
 leave:
 	mdb_cursor_close(mc);
 	return rc;
 }
 
 int mdb_set_compare(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
 {
 	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	txn->mt_dbxs[dbi].md_cmp = cmp;
 	return MDB_SUCCESS;
 }
 
 int mdb_set_dupsort(MDB_txn *txn, MDB_dbi dbi, MDB_cmp_func *cmp)
 {
 	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	txn->mt_dbxs[dbi].md_dcmp = cmp;
 	return MDB_SUCCESS;
 }
 
 int mdb_set_relfunc(MDB_txn *txn, MDB_dbi dbi, MDB_rel_func *rel)
 {
 	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	txn->mt_dbxs[dbi].md_rel = rel;
 	return MDB_SUCCESS;
 }
 
 int mdb_set_relctx(MDB_txn *txn, MDB_dbi dbi, void *ctx)
 {
 	if (!TXN_DBI_EXIST(txn, dbi, DB_USRVALID))
 		return EINVAL;
 
 	txn->mt_dbxs[dbi].md_relctx = ctx;
 	return MDB_SUCCESS;
 }
 
 int ESECT
 mdb_env_get_maxkeysize(MDB_env *env)
 {
 	return ENV_MAXKEY(env);
 }
 
 int ESECT
 mdb_reader_list(MDB_env *env, MDB_msg_func *func, void *ctx)
 {
 	unsigned int i, rdrs;
 	MDB_reader *mr;
 	char buf[64];
 	int rc = 0, first = 1;
 
 	if (!env || !func)
 		return -1;
 	if (!env->me_txns) {
 		return func("(no reader locks)\n", ctx);
 	}
 	rdrs = env->me_txns->mti_numreaders;
 	mr = env->me_txns->mti_readers;
 	for (i=0; i<rdrs; i++) {
 		if (mr[i].mr_pid) {
 			txnid_t	txnid = mr[i].mr_txnid;
 			sprintf(buf, txnid == (txnid_t)-1 ?
 				"%10d %"Z"x -\n" : "%10d %"Z"x %"Z"u\n",
 				(int)mr[i].mr_pid, (size_t)mr[i].mr_tid, txnid);
 			if (first) {
 				first = 0;
 				rc = func("    pid     thread     txnid\n", ctx);
 				if (rc < 0)
 					break;
 			}
 			rc = func(buf, ctx);
 			if (rc < 0)
 				break;
 		}
 	}
 	if (first) {
 		rc = func("(no active readers)\n", ctx);
 	}
 	return rc;
 }
 
 /** Insert pid into list if not already present.
  * return -1 if already present.
  */
 static int ESECT
 mdb_pid_insert(MDB_PID_T *ids, MDB_PID_T pid)
 {
 	/* binary search of pid in list */
 	unsigned base = 0;
 	unsigned cursor = 1;
 	int val = 0;
 	unsigned n = ids[0];
 
 	while( 0 < n ) {
 		unsigned pivot = n >> 1;
 		cursor = base + pivot + 1;
 		val = pid - ids[cursor];
 
 		if( val < 0 ) {
 			n = pivot;
 
 		} else if ( val > 0 ) {
 			base = cursor;
 			n -= pivot + 1;
 
 		} else {
 			/* found, so it's a duplicate */
 			return -1;
 		}
 	}
 
 	if( val > 0 ) {
 		++cursor;
 	}
 	ids[0]++;
 	for (n = ids[0]; n > cursor; n--)
 		ids[n] = ids[n-1];
 	ids[n] = pid;
 	return 0;
 }
 
 int ESECT
 mdb_reader_check(MDB_env *env, int *dead)
 {
 	if (!env)
 		return EINVAL;
 	if (dead)
 		*dead = 0;
 	return env->me_txns ? mdb_reader_check0(env, 0, dead) : MDB_SUCCESS;
 }
 
 /** As #mdb_reader_check(). \b rlocked is set if caller locked #me_rmutex. */
 static int ESECT
 mdb_reader_check0(MDB_env *env, int rlocked, int *dead)
 {
 	mdb_mutexref_t rmutex = rlocked ? NULL : env->me_rmutex;
 	unsigned int i, j, rdrs;
 	MDB_reader *mr;
 	MDB_PID_T *pids, pid;
 	int rc = MDB_SUCCESS, count = 0;
 
 	rdrs = env->me_txns->mti_numreaders;
 	pids = malloc((rdrs+1) * sizeof(MDB_PID_T));
 	if (!pids)
 		return ENOMEM;
 	pids[0] = 0;
 	mr = env->me_txns->mti_readers;
 	for (i=0; i<rdrs; i++) {
 		pid = mr[i].mr_pid;
 		if (pid && pid != env->me_pid) {
 			if (mdb_pid_insert(pids, pid) == 0) {
 				if (!mdb_reader_pid(env, Pidcheck, pid)) {
 					/* Stale reader found */
 					j = i;
 					if (rmutex) {
 						if ((rc = LOCK_MUTEX0(rmutex)) != 0) {
 							if ((rc = mdb_mutex_failed(env, rmutex, rc)))
 								break;
 							rdrs = 0; /* the above checked all readers */
 						} else {
 							/* Recheck, a new process may have reused pid */
 							if (mdb_reader_pid(env, Pidcheck, pid))
 								j = rdrs;
 						}
 					}
 					for (; j<rdrs; j++)
 							if (mr[j].mr_pid == pid) {
 								DPRINTF(("clear stale reader pid %u txn %"Z"d",
 									(unsigned) pid, mr[j].mr_txnid));
 								mr[j].mr_pid = 0;
 								count++;
 							}
 					if (rmutex)
 						UNLOCK_MUTEX(rmutex);
 				}
 			}
 		}
 	}
 	free(pids);
 	if (dead)
 		*dead = count;
 	return rc;
 }
 
 #ifdef MDB_ROBUST_SUPPORTED
 /** Handle #LOCK_MUTEX0() failure.
  * Try to repair the lock file if the mutex owner died.
  * @param[in] env	the environment handle
  * @param[in] mutex	LOCK_MUTEX0() mutex
  * @param[in] rc	LOCK_MUTEX0() error (nonzero)
  * @return 0 on success with the mutex locked, or an error code on failure.
  */
 static int ESECT
 mdb_mutex_failed(MDB_env *env, mdb_mutexref_t mutex, int rc)
 {
 	int rlocked, rc2;
 	MDB_meta *meta;
 
 	if (rc == MDB_OWNERDEAD) {
 		/* We own the mutex. Clean up after dead previous owner. */
 		rc = MDB_SUCCESS;
 		rlocked = (mutex == env->me_rmutex);
 		if (!rlocked) {
 			/* Keep mti_txnid updated, otherwise next writer can
 			 * overwrite data which latest meta page refers to.
 			 */
 			meta = mdb_env_pick_meta(env);
 			env->me_txns->mti_txnid = meta->mm_txnid;
 			/* env is hosed if the dead thread was ours */
 			if (env->me_txn) {
 				env->me_flags |= MDB_FATAL_ERROR;
 				env->me_txn = NULL;
 				rc = MDB_PANIC;
 			}
 		}
 		DPRINTF(("%cmutex owner died, %s", (rlocked ? 'r' : 'w'),
 			(rc ? "this process' env is hosed" : "recovering")));
 		rc2 = mdb_reader_check0(env, rlocked, NULL);
 		if (rc2 == 0)
 			rc2 = mdb_mutex_consistent(mutex);
 		if (rc || (rc = rc2)) {
 			DPRINTF(("LOCK_MUTEX recovery failed, %s", mdb_strerror(rc)));
 			UNLOCK_MUTEX(mutex);
 		}
 	} else {
 #ifdef _WIN32
 		rc = ErrCode();
 #endif
 		DPRINTF(("LOCK_MUTEX failed, %s", mdb_strerror(rc)));
 	}
 
 	return rc;
 }
 #endif	/* MDB_ROBUST_SUPPORTED */
 
 #if defined(_WIN32)
 /** Convert \b src to new wchar_t[] string with room for \b xtra extra chars */
 static int ESECT
 utf8_to_utf16(const char *src, MDB_name *dst, int xtra)
 {
 	int rc, need = 0;
 	wchar_t *result = NULL;
 	for (;;) {					/* malloc result, then fill it in */
 		need = MultiByteToWideChar(CP_UTF8, 0, src, -1, result, need);
 		if (!need) {
 			rc = ErrCode();
 			free(result);
 			return rc;
 		}
 		if (!result) {
 			result = malloc(sizeof(wchar_t) * (need + xtra));
 			if (!result)
 				return ENOMEM;
 			continue;
 		}
 		dst->mn_alloced = 1;
 		dst->mn_len = need - 1;
 		dst->mn_val = result;
 		return MDB_SUCCESS;
 	}
 }
 #endif /* defined(_WIN32) */
 /** @} */