lib/xvasprintf.c

   1 /* vasprintf and asprintf with out-of-memory checking.
   2    Copyright (C) 1999, 2002-2004, 2006-2020 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 3 of the License, or
   7    (at your option) 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
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include "xvasprintf.h"
  21
  22 #include <errno.h>
  23 #include <limits.h>
  24 #include <string.h>
  25 #include <stdio.h>
  26
  27 #include "xalloc.h"
  28
  29 /* Checked size_t computations.  */
  30 #include "xsize.h"
  31
  32 static char *
  33 xstrcat (size_t argcount, va_list args)
  34 {
  35   char *result;
  36   va_list ap;
  37   size_t totalsize;
  38   size_t i;
  39   char *p;
  40
  41   /* Determine the total size.  */
  42   totalsize = 0;
  43   va_copy (ap, args);
  44   for (i = argcount; i > 0; i--)
  45     {
  46       const char *next = va_arg (ap, const char *);
  47       totalsize = xsum (totalsize, strlen (next));
  48     }
  49   va_end (ap);
  50
  51   /* Test for overflow in the summing pass above or in (totalsize + 1) below.
  52      Also, don't return a string longer than INT_MAX, for consistency with
  53      vasprintf().  */
  54   if (totalsize == SIZE_MAX || totalsize > INT_MAX)
  55     {
  56       errno = EOVERFLOW;
  57       return NULL;
  58     }
  59
  60   /* Allocate and fill the result string.  */
  61   result = XNMALLOC (totalsize + 1, char);
  62   p = result;
  63   for (i = argcount; i > 0; i--)
  64     {
  65       const char *next = va_arg (args, const char *);
  66       size_t len = strlen (next);
  67       memcpy (p, next, len);
  68       p += len;
  69     }
  70   *p = '\0';
  71
  72   return result;
  73 }
  74
  75 char *
  76 xvasprintf (const char *format, va_list args)
  77 {
  78   char *result;
  79
  80   /* Recognize the special case format = "%s...%s".  It is a frequently used
  81      idiom for string concatenation and needs to be fast.  We don't want to
  82      have a separate function xstrcat() for this purpose.  */
  83   {
  84     size_t argcount = 0;
  85     const char *f;
  86
  87     for (f = format;;)
  88       {
  89         if (*f == '\0')
  90           /* Recognized the special case of string concatenation.  */
  91           return xstrcat (argcount, args);
  92         if (*f != '%')
  93           break;
  94         f++;
  95         if (*f != 's')
  96           break;
  97         f++;
  98         argcount++;
  99       }
 100   }
 101
 102   if (vasprintf (&result, format, args) < 0)
 103     {
 104       if (errno == ENOMEM)
 105         xalloc_die ();
 106       return NULL;
 107     }
 108
 109   return result;
 110 }