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 "includes.h"
  19 #include <stdarg.h>
  20
  21 #include "sprintf_alloc.h"
  22 #include "libbb/libbb.h"
  23
  24 int sprintf_alloc(char **str, const char *fmt, ...)
  25 {
  26     va_list ap;
  27     int n;
  28     unsigned size = 100;
  29
  30     if (!str) {
  31       opkg_msg(ERROR, "Internal error: str=NULL.\n");
  32       return -1;
  33     }
  34     if (!fmt) {
  35       opkg_msg(ERROR, "Internal error: fmt=NULL.\n");
  36       return -1;
  37     }
  38
  39     /* On x86_64 systems, any strings over 100 were segfaulting.
  40        It seems that the ap needs to be reinitalized before every
  41        use of the v*printf() functions. I pulled the functionality out
  42        of vsprintf_alloc and combined it all here instead.
  43     */
  44
  45
  46     /* ripped more or less straight out of PRINTF(3) */
  47
  48     *str = xcalloc(1, size);
  49
  50     while(1) {
  51       va_start(ap, fmt);
  52       n = vsnprintf (*str, size, fmt, ap);
  53       va_end(ap);
  54       /* If that worked, return the size. */
  55       if (n > -1 && n < size)
  56         return n;
  57         /* Else try again with more space. */
  58         if (n > -1)    /* glibc 2.1 */
  59             size = n+1; /* precisely what is needed */
  60         else           /* glibc 2.0 */
  61             size *= 2;  /* twice the old size */
  62         *str = xrealloc(*str, size);
  63     }
  64
  65     return -1; /* Just to be correct - it probably won't get here */
  66 }