vsnprintf.c revision 165903 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 4. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)vsnprintf.c	8.1 (Berkeley) 6/4/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: head/lib/libc/stdio/vsnprintf.c 165903 2007-01-09 00:28:16Z imp $");
38
39#include <limits.h>
40#include <stdio.h>
41#include "local.h"
42
43int
44vsnprintf(char * __restrict str, size_t n, const char * __restrict fmt,
45    __va_list ap)
46{
47	size_t on;
48	int ret;
49	char dummy[2];
50	FILE f;
51	struct __sFILEX ext;
52
53	on = n;
54	if (n != 0)
55		n--;
56	if (n > INT_MAX)
57		n = INT_MAX;
58	/* Stdio internals do not deal correctly with zero length buffer */
59	if (n == 0) {
60		if (on > 0)
61	  		*str = '\0';
62		str = dummy;
63		n = 1;
64	}
65	f._file = -1;
66	f._flags = __SWR | __SSTR;
67	f._bf._base = f._p = (unsigned char *)str;
68	f._bf._size = f._w = n;
69	f._extra = &ext;
70	INITEXTRA(&f);
71	ret = __vfprintf(&f, fmt, ap);
72	if (on > 0)
73		*f._p = '\0';
74	return (ret);
75}
76