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 sprintf_alloc(char **str, const char *fmt, ...)
  22 {
  23         va_list ap;
  24         int n;
  25         unsigned int size = 0;
  26
  27         *str = NULL;
  28
  29         for (;;) {
  30                 va_start(ap, fmt);
  31                 n = vsnprintf(*str, size, fmt, ap);
  32                 va_end(ap);
  33
  34                 if (n < 0) {
  35                         fprintf(stderr, "%s: encountered an output or encoding"
  36                                 " error during vsnprintf.\n", __FUNCTION__);
  37                         exit(EXIT_FAILURE);
  38                 }
  39
  40                 if (n < size)
  41                         break;
  42
  43                 /* Truncated, try again with more space. */
  44                 size = n + 1;
  45                 *str = xrealloc(*str, size);
  46         }
  47 }