libopkg/sprintf_alloc.c

   1 /* sprintf_alloc.c -- like sprintf with memory allocation
   2
   3    Carl D. Worth
   4
   5    Copyright (C) 2001 University of Southern California
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2, or (at your option)
  10    any later version.
  11
  12    This program 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
  15    GNU General Public License for more details.
  16 */
  17
  18 #include <stdarg.h>
  19
  20 #include "sprintf_alloc.h"
  21 #include "libbb/libbb.h"
  22
  23 int sprintf_alloc(char **str, const char *fmt, ...)
  24 {
  25     va_list ap;
  26     int n;
  27     unsigned size = 100;
  28
  29     if (!str) {
  30       opkg_msg(ERROR, "Internal error: str=NULL.\n");
  31       return -1;
  32     }
  33     if (!fmt) {
  34       opkg_msg(ERROR, "Internal error: fmt=NULL.\n");
  35       return -1;
  36     }
  37
  38     /* On x86_64 systems, any strings over 100 were segfaulting.
  39        It seems that the ap needs to be reinitalized before every
  40        use of the v*printf() functions. I pulled the functionality out
  41        of vsprintf_alloc and combined it all here instead.
  42     */
  43
  44
  45     /* ripped more or less straight out of PRINTF(3) */
  46
  47     *str = xcalloc(1, size);
  48
  49     while(1) {
  50       va_start(ap, fmt);
  51       n = vsnprintf (*str, size, fmt, ap);
  52       va_end(ap);
  53       /* If that worked, return the size. */
  54       if (n > -1 && n < size)
  55         return n;
  56         /* Else try again with more space. */
  57         if (n > -1)    /* glibc 2.1 */
  58             size = n+1; /* precisely what is needed */
  59         else           /* glibc 2.0 */
  60             size *= 2;  /* twice the old size */
  61         *str = xrealloc(*str, size);
  62     }
  63
  64     return -1; /* Just to be correct - it probably won't get here */
  65 }