libc/stdio/vsnprintf.c

1 /* $OpenBSD: vsnprintf.c,v 1.17 2025年08月08日 15:58:53 yasuoka Exp $ */
2 /*-
3 * Copyright (c) 1990, 1993
4 * The Regents of the University of California. All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <limits.h>
35#include <stdio.h>
36#include <string.h>
37#include "local.h"
38
39 int
40 vsnprintf(char *str, size_t n, const char *fmt, __va_list ap)
41{
42 int ret;
43 char dummy;
44 FILE f = FILEINIT(__SWR | __SSTR);
45
46 /* While snprintf(3) specifies size_t stdio uses an int internally */
47 if (n > INT_MAX)
48 n = INT_MAX;
49 /* Stdio internals do not deal correctly with zero length buffer */
50 if (n == 0) {
51 str = &dummy;
52 n = 1;
53 }
54 f._bf._base = f._p = (unsigned char *)str;
55 f._bf._size = f._w = n - 1;
56 ret = __vfprintf(&f, fmt, ap);
57 *f._p = '0円';
58 return (ret);
59}
60 DEF_STRONG(vsnprintf);
61