gl/vsnprintf.c

   1 /* Formatted output to strings.
   2    Copyright (C) 2004, 2006-2010 Free Software Foundation, Inc.
   3    Written by Simon Josefsson and Yoann Vandoorselaere <yoann@prelude-ids.org>.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License along
  16    with this program; if not, write to the Free Software Foundation,
  17    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 /* Specification.  */
  24 #include <stdio.h>
  25
  26 #include <errno.h>
  27 #include <limits.h>
  28 #include <stdarg.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31
  32 #include "vasnprintf.h"
  33
  34 /* Print formatted output to string STR.  Similar to vsprintf, but
  35    additional length SIZE limit how much is written into STR.  Returns
  36    string length of formatted string (which may be larger than SIZE).
  37    STR may be NULL, in which case nothing will be written.  On error,
  38    return a negative value.  */
  39 int
  40 vsnprintf (char *str, size_t size, const char *format, va_list args)
  41 {
  42   char *output;
  43   size_t len;
  44   size_t lenbuf = size;
  45
  46   output = vasnprintf (str, &lenbuf, format, args);
  47   len = lenbuf;
  48
  49   if (!output)
  50     return -1;
  51
  52   if (output != str)
  53     {
  54       if (size)
  55         {
  56           size_t pruned_len = (len < size ? len : size - 1);
  57           memcpy (str, output, pruned_len);
  58           str[pruned_len] = '\0';
  59         }
  60
  61       free (output);
  62     }
  63
  64   if (len > INT_MAX)
  65     {
  66       errno = EOVERFLOW;
  67       return -1;
  68     }
  69
  70   return len;
  71 }