datefmt

commit a59cca9f3b88581ba42dd79663fbccbf0b2d8a93
Author: William Casarin <jb55@jb55.com>
Date:   Fri,  9 Oct 2020 08:40:44 -0700

initial commit

Diffstat:
A
.envrc
 | 
1
+
A
.gitignore
 | 
1
+
A
Makefile
 | 
10
++++++++++
A
datefmt.c
 | 
140
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
default.nix
 | 
6
++++++

5 files changed, 158 insertions(+), 0 deletions(-)
diff --git a/.envrc b/.envrc
@@ -0,0 +1 @@
+use nix
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1 @@
+/datefmt
diff --git a/Makefile b/Makefile
@@ -0,0 +1,10 @@
+
+CFLAGS = -Wall -Werror -std=c89
+
+datefmt: datefmt.c
+	$(CC) $(CFLAGS) $< -o $@
+
+clean: fake
+	rm -f datefmt
+
+.PHONY: fake
diff --git a/datefmt.c b/datefmt.c
@@ -0,0 +1,140 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+
+enum state {
+	BEGIN,
+	WAIT,
+	BOUNDARY,
+	MIDDLE,
+};
+
+struct parser {
+	enum state state;
+	unsigned char *buf;
+	size_t len;
+	int n_digits;
+	char digits[12];
+};
+
+static enum state update_state(int c, enum state state)
+{
+	if (c == -1 || isspace(c)) {
+		if (state == WAIT || state == BEGIN) {
+			return BOUNDARY;
+		} else if (state == MIDDLE) {
+			return BOUNDARY;
+		}
+	} else if (isdigit(c)) {
+		if (state == BOUNDARY) {
+			return MIDDLE;
+		} else if (state == BEGIN) {
+                        return MIDDLE;
+                }
+	}
+
+	if (state == BOUNDARY || state == BEGIN) {
+		return WAIT;
+	}
+
+	return state;
+}
+
+static enum state doaction(int c, enum state new_state, struct parser *parser)
+{
+        char charbuf[2];
+        unsigned ts;
+
+        if (c == -1)
+                charbuf[0] = 0;
+        else {
+                charbuf[0] = (char)c;
+                charbuf[1] = 0;
+        }
+
+        if (parser->state == MIDDLE && new_state == BOUNDARY) {
+                ts = strtoul(parser->digits, NULL, 10);
+                /* found date */
+                printf("[%d]%s", ts, charbuf);
+        } else if (new_state == MIDDLE) {
+                if (parser->n_digits < 10) {
+                        parser->digits[parser->n_digits++] = (char)c;
+                        parser->digits[parser->n_digits] = 0;
+                } else {
+                        new_state = WAIT;
+                        printf("%.*s%s", parser->n_digits, parser->digits, charbuf);
+                        parser->n_digits = 0;
+                }
+        } else {
+                if (c != -1)
+                        fputc(c, stdout);
+        }
+
+        return new_state;
+}
+
+/* static const char *state_name(enum state state) */
+/* { */
+/*         switch (state) { */
+/*         case BOUNDARY: return "BOUNDARY"; */
+/*         case WAIT: return "WAIT"; */
+/*         case MIDDLE: return "MIDDLE"; */
+/*         case BEGIN: return "BEGIN"; */
+/*         } */
+/*         return "UNKN"; */
+/* } */
+
+
+
+static void process(struct parser *parser, int last)
+{
+	enum state new_state;
+	int i;
+	int c;
+
+	for (i = 0; i < parser->len+last; i++) {
+                if (last && i == parser->len)
+                        c = -1;
+		else
+                        c = parser->buf[i];
+
+		/* transition state */
+		new_state = update_state(c, parser->state);
+
+                /* debug */
+                /* printf("%d | %s -> %s\n", c, state_name(parser->state), state_name(new_state)); */
+
+		/* action */
+                new_state = doaction(c, new_state, parser);
+
+		if (new_state == BOUNDARY) {
+			parser->n_digits = 0;
+		}
+
+		parser->state = new_state;
+	}
+}
+
+#define READSIZE 4096
+
+static void parser_init(struct parser *parser)
+{
+	static unsigned char buf[READSIZE];
+	parser->buf = buf;
+	parser->state = BEGIN;
+	parser->len = 0;
+	parser->n_digits = 0;
+}
+
+int main(int argc, const char *argv[])
+{
+	struct parser parser;
+	parser_init(&parser);
+
+	do {
+		parser.len = fread(parser.buf, 1, READSIZE, stdin);
+		process(&parser, parser.len != READSIZE);
+	} while (parser.len == READSIZE);
+
+	return 0;
+}
diff --git a/default.nix b/default.nix
@@ -0,0 +1,6 @@
+{ pkgs ? import <nixpkgs> {} }:
+with pkgs;
+stdenv.mkDerivation {
+  name = "datefmt";
+  nativeBuildInputs = [ ];
+}