gl/xvasprintf.c

   1 /* vasprintf and asprintf with out-of-memory checking.
   2    Copyright (C) 1999, 2002-2004, 2006, 2007 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  17
  18 #include <config.h>
  19
  20 /* Specification.  */
  21 #include "xvasprintf.h"
  22
  23 #include <errno.h>
  24 #include <limits.h>
  25 #include <string.h>
  26 #include <stdio.h>
  27
  28 #include "xalloc.h"
  29
  30 /* Checked size_t computations.  */
  31 #include "xsize.h"
  32
  33 /* Some systems, like OSF/1 4.0 and Woe32, don't have EOVERFLOW.  */
  34 #ifndef EOVERFLOW
  35 # define EOVERFLOW E2BIG
  36 #endif
  37
  38 static inline char *
  39 xstrcat (size_t argcount, va_list args)
  40 {
  41   char *result;
  42   va_list ap;
  43   size_t totalsize;
  44   size_t i;
  45   char *p;
  46
  47   /* Determine the total size.  */
  48   totalsize = 0;
  49   va_copy (ap, args);
  50   for (i = argcount; i > 0; i--)
  51     {
  52       const char *next = va_arg (ap, const char *);
  53       totalsize = xsum (totalsize, strlen (next));
  54     }
  55   va_end (ap);
  56
  57   /* Test for overflow in the summing pass above or in (totalsize + 1) below.
  58      Also, don't return a string longer than INT_MAX, for consistency with
  59      vasprintf().  */
  60   if (totalsize == SIZE_MAX || totalsize > INT_MAX)
  61     {
  62       errno = EOVERFLOW;
  63       return NULL;
  64     }
  65
  66   /* Allocate and fill the result string.  */
  67   result = XNMALLOC (totalsize + 1, char);
  68   p = result;
  69   for (i = argcount; i > 0; i--)
  70     {
  71       const char *next = va_arg (args, const char *);
  72       size_t len = strlen (next);
  73       memcpy (p, next, len);
  74       p += len;
  75     }
  76   *p = '\0';
  77
  78   return result;
  79 }
  80
  81 char *
  82 xvasprintf (const char *format, va_list args)
  83 {
  84   char *result;
  85
  86   /* Recognize the special case format = "%s...%s".  It is a frequently used
  87      idiom for string concatenation and needs to be fast.  We don't want to
  88      have a separate function xstrcat() for this purpose.  */
  89   {
  90     size_t argcount = 0;
  91     const char *f;
  92
  93     for (f = format;;)
  94       {
  95         if (*f == '\0')
  96           /* Recognized the special case of string concatenation.  */
  97           return xstrcat (argcount, args);
  98         if (*f != '%')
  99           break;
 100         f++;
 101         if (*f != 's')
 102           break;
 103         f++;
 104         argcount++;
 105       }
 106   }
 107
 108   if (vasprintf (&result, format, args) < 0)
 109     {
 110       if (errno == ENOMEM)
 111         xalloc_die ();
 112       return NULL;
 113     }
 114
 115   return result;
 116 }