damus

htable.c (11777B)

---

 /* Licensed under LGPLv2+ - see LICENSE file for details */
 #include <ccan/htable/htable.h>
 #include <ccan/compiler/compiler.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <limits.h>
 #include <stdbool.h>
 #include <assert.h>
 #include <string.h>
 
 /* We use 0x1 as deleted marker. */
 #define HTABLE_DELETED (0x1)
 
 /* perfect_bitnum 63 means there's no perfect bitnum */
 #define NO_PERFECT_BIT (sizeof(uintptr_t) * CHAR_BIT - 1)
 
 static void *htable_default_alloc(struct htable *ht, size_t len)
 {
 	return calloc(len, 1);
 }
 
 static void htable_default_free(struct htable *ht, void *p)
 {
 	free(p);
 }
 
 static void *(*htable_alloc)(struct htable *, size_t) = htable_default_alloc;
 static void (*htable_free)(struct htable *, void *) = htable_default_free;
 
 void htable_set_allocator(void *(*alloc)(struct htable *, size_t len),
 			  void (*free)(struct htable *, void *p))
 {
 	if (!alloc)
 		alloc = htable_default_alloc;
 	if (!free)
 		free = htable_default_free;
 	htable_alloc = alloc;
 	htable_free = free;
 }
 
 /* We clear out the bits which are always the same, and put metadata there. */
 static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,
 					   uintptr_t e)
 {
 	return e & ht->common_mask;
 }
 
 static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)
 {
 	return (void *)((e & ~ht->common_mask) | ht->common_bits);
 }
 
 static inline uintptr_t make_hval(const struct htable *ht,
 				  const void *p, uintptr_t bits)
 {
 	return ((uintptr_t)p & ~ht->common_mask) | bits;
 }
 
 static inline bool entry_is_valid(uintptr_t e)
 {
 	return e > HTABLE_DELETED;
 }
 
 static inline uintptr_t ht_perfect_mask(const struct htable *ht)
 {
 	return (uintptr_t)2 << ht->perfect_bitnum;
 }
 
 static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
 					  size_t hash)
 {
 	/* Shuffling the extra bits (as specified in mask) down the
 	 * end is quite expensive.  But the lower bits are redundant, so
 	 * we fold the value first. */
 	return (hash ^ (hash >> ht->bits))
 		& ht->common_mask & ~ht_perfect_mask(ht);
 }
 
 void htable_init(struct htable *ht,
 		 size_t (*rehash)(const void *elem, void *priv), void *priv)
 {
 	struct htable empty = HTABLE_INITIALIZER(empty, NULL, NULL);
 	*ht = empty;
 	ht->rehash = rehash;
 	ht->priv = priv;
 	ht->table = &ht->common_bits;
 }
 
 /* Fill to 87.5% */
 static inline size_t ht_max(const struct htable *ht)
 {
 	return ((size_t)7 << ht->bits) / 8;
 }
 
 /* Clean deleted if we're full, and more than 12.5% deleted */
 static inline size_t ht_max_deleted(const struct htable *ht)
 {
 	return ((size_t)1 << ht->bits) / 8;
 }
 
 bool htable_init_sized(struct htable *ht,
 		       size_t (*rehash)(const void *, void *),
 		       void *priv, size_t expect)
 {
 	htable_init(ht, rehash, priv);
 
 	/* Don't go insane with sizing. */
 	for (ht->bits = 1; ht_max(ht) < expect; ht->bits++) {
 		if (ht->bits == 30)
 			break;
 	}
 
 	ht->table = htable_alloc(ht, sizeof(size_t) << ht->bits);
 	if (!ht->table) {
 		ht->table = &ht->common_bits;
 		return false;
 	}
 	(void)htable_debug(ht, HTABLE_LOC);
 	return true;
 }
 	
 void htable_clear(struct htable *ht)
 {
 	if (ht->table != &ht->common_bits)
 		htable_free(ht, (void *)ht->table);
 	htable_init(ht, ht->rehash, ht->priv);
 }
 
 bool htable_copy_(struct htable *dst, const struct htable *src)
 {
 	uintptr_t *htable = htable_alloc(dst, sizeof(size_t) << src->bits);
 
 	if (!htable)
 		return false;
 
 	*dst = *src;
 	dst->table = htable;
 	memcpy(dst->table, src->table, sizeof(size_t) << src->bits);
 	return true;
 }
 
 static size_t hash_bucket(const struct htable *ht, size_t h)
 {
 	return h & ((1 << ht->bits)-1);
 }
 
 static void *htable_val(const struct htable *ht,
 			struct htable_iter *i, size_t hash, uintptr_t perfect)
 {
 	uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect;
 
 	while (ht->table[i->off]) {
 		if (ht->table[i->off] != HTABLE_DELETED) {
 			if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
 				return get_raw_ptr(ht, ht->table[i->off]);
 		}
 		i->off = (i->off + 1) & ((1 << ht->bits)-1);
 		h2 &= ~perfect;
 	}
 	return NULL;
 }
 
 void *htable_firstval_(const struct htable *ht,
 		       struct htable_iter *i, size_t hash)
 {
 	i->off = hash_bucket(ht, hash);
 	return htable_val(ht, i, hash, ht_perfect_mask(ht));
 }
 
 void *htable_nextval_(const struct htable *ht,
 		      struct htable_iter *i, size_t hash)
 {
 	i->off = (i->off + 1) & ((1 << ht->bits)-1);
 	return htable_val(ht, i, hash, 0);
 }
 
 void *htable_first_(const struct htable *ht, struct htable_iter *i)
 {
 	for (i->off = 0; i->off < (size_t)1 << ht->bits; i->off++) {
 		if (entry_is_valid(ht->table[i->off]))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 	return NULL;
 }
 
 void *htable_next_(const struct htable *ht, struct htable_iter *i)
 {
 	for (i->off++; i->off < (size_t)1 << ht->bits; i->off++) {
 		if (entry_is_valid(ht->table[i->off]))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 	return NULL;
 }
 
 void *htable_prev_(const struct htable *ht, struct htable_iter *i)
 {
 	for (;;) {
 		if (!i->off)
 			return NULL;
 		i->off--;
 		if (entry_is_valid(ht->table[i->off]))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 }
 
 /* Another bit currently in mask needs to be exposed, so that a bucket with p in
  * it won't appear invalid */
 static COLD void unset_another_common_bit(struct htable *ht,
 					  uintptr_t *maskdiff,
 					  const void *p)
 {
 	size_t i;
 
 	for (i = sizeof(uintptr_t) * CHAR_BIT - 1; i > 0; i--) {
 		if (((uintptr_t)p & ((uintptr_t)1 << i))
 		    && ht->common_mask & ~*maskdiff & ((uintptr_t)1 << i))
 			break;
 	}
 	/* There must have been one, right? */
 	assert(i > 0);
 
 	*maskdiff |= ((uintptr_t)1 << i);
 }
 
 /* We want to change the common mask: this fixes up the table */
 static COLD void fixup_table_common(struct htable *ht, uintptr_t maskdiff)
 {
 	size_t i;
 	uintptr_t bitsdiff;
 
 again:
 	bitsdiff = ht->common_bits & maskdiff;
 
 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
 		uintptr_t e;
 		if (!entry_is_valid(e = ht->table[i]))
 			continue;
 
 		/* Clear the bits no longer in the mask, set them as
 		 * expected. */
 		e &= ~maskdiff;
 		e |= bitsdiff;
 		/* If this made it invalid, restart with more exposed */
 		if (!entry_is_valid(e)) {
 			unset_another_common_bit(ht, &maskdiff, get_raw_ptr(ht, e));
 			goto again;
 		}
 		ht->table[i] = e;
 	}
 
 	/* Take away those bits from our mask, bits and perfect bit. */
 	ht->common_mask &= ~maskdiff;
 	ht->common_bits &= ~maskdiff;
 	if (ht_perfect_mask(ht) & maskdiff)
 		ht->perfect_bitnum = NO_PERFECT_BIT;
 }
 
 /* Limited recursion */
 static void ht_add(struct htable *ht, const void *new, size_t h);
 
 /* We tried to add this entry, but it looked invalid!  We need to
  * let another pointer bit through mask */
 static COLD void update_common_fix_invalid(struct htable *ht, const void *p, size_t h)
 {
 	uintptr_t maskdiff;
 
 	assert(ht->elems != 0);
 
 	maskdiff = 0;
 	unset_another_common_bit(ht, &maskdiff, p);
 	fixup_table_common(ht, maskdiff);
 
 	/* Now won't recurse */
 	ht_add(ht, p, h);
 }
 
 /* This does not expand the hash table, that's up to caller. */
 static void ht_add(struct htable *ht, const void *new, size_t h)
 {
 	size_t i;
 	uintptr_t perfect = ht_perfect_mask(ht);
 
 	i = hash_bucket(ht, h);
 
 	while (entry_is_valid(ht->table[i])) {
 		perfect = 0;
 		i = (i + 1) & ((1 << ht->bits)-1);
 	}
 	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
 	if (!entry_is_valid(ht->table[i]))
 		update_common_fix_invalid(ht, new, h);
 }
 
 static COLD bool double_table(struct htable *ht)
 {
 	unsigned int i;
 	size_t oldnum = (size_t)1 << ht->bits;
 	uintptr_t *oldtable, e;
 
 	oldtable = ht->table;
 	ht->table = htable_alloc(ht, sizeof(size_t) << (ht->bits+1));
 	if (!ht->table) {
 		ht->table = oldtable;
 		return false;
 	}
 	ht->bits++;
 
 	/* If we lost our "perfect bit", get it back now. */
 	if (ht->perfect_bitnum == NO_PERFECT_BIT && ht->common_mask) {
 		for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) {
 			if (ht->common_mask & ((size_t)2 << i)) {
 				ht->perfect_bitnum = i;
 				break;
 			}
 		}
 	}
 
 	if (oldtable != &ht->common_bits) {
 		for (i = 0; i < oldnum; i++) {
 			if (entry_is_valid(e = oldtable[i])) {
 				void *p = get_raw_ptr(ht, e);
 				ht_add(ht, p, ht->rehash(p, ht->priv));
 			}
 		}
 		htable_free(ht, oldtable);
 	}
 	ht->deleted = 0;
 
 	(void)htable_debug(ht, HTABLE_LOC);
 	return true;
 }
 
 static COLD void rehash_table(struct htable *ht)
 {
 	size_t start, i;
 	uintptr_t e, perfect = ht_perfect_mask(ht);
 
 	/* Beware wrap cases: we need to start from first empty bucket. */
 	for (start = 0; ht->table[start]; start++);
 
 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
 		size_t h = (i + start) & ((1 << ht->bits)-1);
 		e = ht->table[h];
 		if (!e)
 			continue;
 		if (e == HTABLE_DELETED)
 			ht->table[h] = 0;
 		else if (!(e & perfect)) {
 			void *p = get_raw_ptr(ht, e);
 			ht->table[h] = 0;
 			ht_add(ht, p, ht->rehash(p, ht->priv));
 		}
 	}
 	ht->deleted = 0;
 	(void)htable_debug(ht, HTABLE_LOC);
 }
 
 /* We stole some bits, now we need to put them back... */
 static COLD void update_common(struct htable *ht, const void *p)
 {
 	uintptr_t maskdiff;
 
 	if (ht->elems == 0) {
 		ht->common_mask = -1;
 		ht->common_bits = ((uintptr_t)p & ht->common_mask);
 		ht->perfect_bitnum = 0;
 		(void)htable_debug(ht, HTABLE_LOC);
 		return;
 	}
 
 	/* Find bits which are unequal to old common set. */
 	maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);
 
 	fixup_table_common(ht, maskdiff);
 	(void)htable_debug(ht, HTABLE_LOC);
 }
 
 bool htable_add_(struct htable *ht, size_t hash, const void *p)
 {
 	/* Cannot insert NULL, or (void *)1. */
 	assert(p);
 	assert(entry_is_valid((uintptr_t)p));
 
 	/* Getting too full? */
 	if (ht->elems+1 + ht->deleted > ht_max(ht)) {
 		/* If we're more than 1/8 deleted, clean those,
 		 * otherwise double table size. */
 		if (ht->deleted > ht_max_deleted(ht))
 			rehash_table(ht);
 		else if (!double_table(ht))
 			return false;
 	}
 	if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
 		update_common(ht, p);
 
 	ht_add(ht, p, hash);
 	ht->elems++;
 	return true;
 }
 
 bool htable_del_(struct htable *ht, size_t h, const void *p)
 {
 	struct htable_iter i;
 	void *c;
 
 	for (c = htable_firstval(ht,&i,h); c; c = htable_nextval(ht,&i,h)) {
 		if (c == p) {
 			htable_delval(ht, &i);
 			return true;
 		}
 	}
 	return false;
 }
 
 void htable_delval_(struct htable *ht, struct htable_iter *i)
 {
 	assert(i->off < (size_t)1 << ht->bits);
 	assert(entry_is_valid(ht->table[i->off]));
 
 	ht->elems--;
 	/* Cheap test: if the next bucket is empty, don't need delete marker */
 	if (ht->table[hash_bucket(ht, i->off+1)] != 0) {
 		ht->table[i->off] = HTABLE_DELETED;
 		ht->deleted++;
 	} else
 		ht->table[i->off] = 0;
 }
 
 void *htable_pick_(const struct htable *ht, size_t seed, struct htable_iter *i)
 {
 	void *e;
 	struct htable_iter unwanted;
 
 	if (!i)
 		i = &unwanted;
 	i->off = seed % ((size_t)1 << ht->bits);
 	e = htable_next(ht, i);
 	if (!e)
 		e = htable_first(ht, i);
 	return e;
 }
 
 struct htable *htable_check(const struct htable *ht, const char *abortstr)
 {
 	void *p;
 	struct htable_iter i;
 	size_t n = 0;
 
 	/* Use non-DEBUG versions here, to avoid infinite recursion with
 	 * CCAN_HTABLE_DEBUG! */
 	for (p = htable_first_(ht, &i); p; p = htable_next_(ht, &i)) {
 		struct htable_iter i2;
 		void *c;
 		size_t h = ht->rehash(p, ht->priv);
 		bool found = false;
 
 		n++;
 
 		/* Open-code htable_get to avoid CCAN_HTABLE_DEBUG */
 		for (c = htable_firstval_(ht, &i2, h);
 		     c;
 		     c = htable_nextval_(ht, &i2, h)) {
 			if (c == p) {
 				found = true;
 				break;
 			}
 		}
 
 		if (!found) {
 			if (abortstr) {
 				fprintf(stderr,
 					"%s: element %p in position %zu"
 					" cannot find itself\n",
 					abortstr, p, i.off);
 				abort();
 			}
 			return NULL;
 		}
 	}
 	if (n != ht->elems) {
 		if (abortstr) {
 			fprintf(stderr,
 				"%s: found %zu elems, expected %zu\n",
 				abortstr, n, ht->elems);
 			abort();
 		}
 		return NULL;
 	}
 
 	return (struct htable *)ht;
 }