lib/vsnprintf.c

   1 /* Formatted output to strings.
   2    Copyright (C) 2004, 2006-2024 Free Software Foundation, Inc.
   3    Written by Simon Josefsson and Yoann Vandoorselaere <yoann@prelude-ids.org>.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifdef HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 /* Specification.  */
  23 #include <stdio.h>
  24
  25 #include <errno.h>
  26 #include <limits.h>
  27 #include <stdarg.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30
  31 #include "vasnprintf.h"
  32
  33 /* Print formatted output to string STR.  Similar to vsprintf, but
  34    additional length SIZE limit how much is written into STR.  Returns
  35    string length of formatted string (which may be larger than SIZE).
  36    STR may be NULL, in which case nothing will be written.  On error,
  37    return a negative value.  */
  38 int
  39 vsnprintf (char *str, size_t size, const char *format, va_list args)
  40 {
  41   char *output;
  42   size_t len;
  43   size_t lenbuf = size;
  44
  45   output = vasnprintf (str, &lenbuf, format, args);
  46   len = lenbuf;
  47
  48   if (!output)
  49     return -1;
  50
  51   if (output != str)
  52     {
  53       if (size)
  54         {
  55           size_t pruned_len = (len < size ? len : size - 1);
  56           memcpy (str, output, pruned_len);
  57           str[pruned_len] = '\0';
  58         }
  59
  60       free (output);
  61     }
  62
  63   if (len > INT_MAX)
  64     {
  65       errno = EOVERFLOW;
  66       return -1;
  67     }
  68
  69   return len;
  70 }