libopkg/sprintf_alloc.c

   1 /* sprintf_alloc.c -- like sprintf with memory allocation
   2
   3    Copyright (C) 2010 Ubiq Technologies <graham.gower@gmail.com>
   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 2, 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
  16 #include <stdarg.h>
  17
  18 #include "sprintf_alloc.h"
  19 #include "libbb/libbb.h"
  20
  21 void
  22 sprintf_alloc(char **str, const char *fmt, ...)
  23 {
  24         va_list ap;
  25         int n;
  26         unsigned int size = 0;
  27
  28         *str = NULL;
  29
  30         for (;;) {
  31                 va_start(ap, fmt);
  32                 n = vsnprintf (*str, size, fmt, ap);
  33                 va_end(ap);
  34
  35                 if (n < 0) {
  36                         fprintf(stderr, "%s: encountered an output or encoding"
  37                                         " error during vsnprintf.\n",
  38                                         __FUNCTION__);
  39                         exit(EXIT_FAILURE);
  40                 }
  41
  42                 if (n < size)
  43                         break;
  44
  45                 /* Truncated, try again with more space. */
  46                 size = n+1;
  47                 *str = xrealloc(*str, size);
  48         }
  49 }