snprintf.c
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1 /*
2  * C99-compatible snprintf() and vsnprintf() implementations
3  * Copyright (c) 2012 Ronald S. Bultje <rsbultje@gmail.com>
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include <stdio.h>
23 #include <stdarg.h>
24 #include <limits.h>
25 #include <string.h>
26 
27 #include "libavutil/error.h"
28 
29 #if !defined(va_copy) && defined(_MSC_VER)
30 #define va_copy(dst, src) ((dst) = (src))
31 #endif
32 
33 int avpriv_snprintf(char *s, size_t n, const char *fmt, ...)
34 {
35  va_list ap;
36  int ret;
37 
38  va_start(ap, fmt);
39  ret = avpriv_vsnprintf(s, n, fmt, ap);
40  va_end(ap);
41 
42  return ret;
43 }
44 
45 int avpriv_vsnprintf(char *s, size_t n, const char *fmt,
46  va_list ap)
47 {
48  int ret;
49  va_list ap_copy;
50 
51  if (n == 0)
52  return _vscprintf(fmt, ap);
53  else if (n > INT_MAX)
54  return AVERROR(EOVERFLOW);
55 
56  /* we use n - 1 here because if the buffer is not big enough, the MS
57  * runtime libraries don't add a terminating zero at the end. MSDN
58  * recommends to provide _snprintf/_vsnprintf() a buffer size that
59  * is one less than the actual buffer, and zero it before calling
60  * _snprintf/_vsnprintf() to workaround this problem.
61  * See http://msdn.microsoft.com/en-us/library/1kt27hek(v=vs.80).aspx */
62  memset(s, 0, n);
63  va_copy(ap_copy, ap);
64  ret = _vsnprintf(s, n - 1, fmt, ap_copy);
65  va_end(ap_copy);
66  if (ret == -1)
67  ret = _vscprintf(fmt, ap);
68 
69  return ret;
70 }