vasprintf.c revision 15931 
1/*-
2 * Copyright (c) 1996  Peter Wemm <peter@freebsd.org>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26#if defined(LIBC_RCS) && !defined(lint)
27static char rcsid[] = "$Id$";
28#endif /* LIBC_RCS and not lint */
29
30#include <stdio.h>
31#include <stdlib.h>
32
33#if __STDC__
34#include <stdarg.h>
35#else
36#include <varargs.h>
37#endif
38
39#define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */
40
41struct bufcookie {
42	char	*base;	/* start of buffer */
43	int	size;
44	int	left;
45};
46
47static int
48writehook(cookie, buf, len)
49	void *cookie;
50	char *buf;
51	int   len;
52{
53	struct bufcookie *h = (struct bufcookie *)cookie;
54
55	if (len == 0)
56		return 0;
57
58	if (len > h->left) {
59		/* grow malloc region */
60		h->left = h->left + len + CHUNK_SPARE;
61		h->size = h->size + len + CHUNK_SPARE;
62		h->base = realloc(h->base, h->size);
63		if (h->base == NULL)
64			return (-1);
65	}
66	/* "write" it */
67	(void)memcpy(h->base + h->size - h->left, buf, len);
68	h->left -= len;
69	return (0);
70}
71
72
73int
74vasprintf(str, fmt, ap)
75	char **str;
76	const char *fmt;
77	va_list ap;
78{
79	int ret;
80	FILE *f;
81	struct bufcookie h;
82
83	h.base = malloc(CHUNK_SPARE);
84	if (h.base == NULL)
85		return (-1);
86	h.size = CHUNK_SPARE;
87	h.left = CHUNK_SPARE;
88
89	f = funopen(&h, NULL, writehook, NULL, NULL);
90	if (f == NULL) {
91		free(h.base);
92		return (-1);
93	}
94	ret = vfprintf(f, fmt, ap);
95	fclose(f);
96	if (ret < 0) {
97		free(h.base);
98		return (-1);
99	}
100	if (h.base == NULL)	/* failed to realloc in writehook */
101		return (-1);
102
103	h.base[h.size - h.left] = '\0';
104	*str = realloc(h.base, h.size - h.left + 1);
105	if (*str == NULL)	/* failed to realloc it to actual size */
106		return -1;
107	return (ret);
108}
109