compat/msvcrt/snprintf.c

   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 }