lib/memcoll.c

   1 /* Locale-specific memory comparison.
   2    Copyright (C) 1999, 2002, 2003 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
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* Contributed by Paul Eggert <eggert@twinsun.com>.  */
  19
  20 #if HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include "memcoll.h"
  25
  26 #include <errno.h>
  27 #ifndef errno
  28 extern int errno;
  29 #endif
  30
  31 #include <string.h>
  32
  33 /* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
  34    to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
  35    adjacent.  Perhaps temporarily modify the bytes after S1 and S2,
  36    but restore their original contents before returning.  Set errno to an
  37    error number if there is an error, and to zero otherwise.  */
  38 int
  39 memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
  40 {
  41   int diff;
  42
  43 #if HAVE_STRCOLL
  44
  45   char n1 = s1[s1len];
  46   char n2 = s2[s2len];
  47
  48   s1[s1len++] = '\0';
  49   s2[s2len++] = '\0';
  50
  51   while (! (errno = 0, (diff = strcoll (s1, s2)) || errno))
  52     {
  53       /* strcoll found no difference, but perhaps it was fooled by NUL
  54          characters in the data.  Work around this problem by advancing
  55          past the NUL chars.  */
  56       size_t size1 = strlen (s1) + 1;
  57       size_t size2 = strlen (s2) + 1;
  58       s1 += size1;
  59       s2 += size2;
  60       s1len -= size1;
  61       s2len -= size2;
  62
  63       if (s1len == 0)
  64         {
  65           if (s2len != 0)
  66             diff = -1;
  67           break;
  68         }
  69       else if (s2len == 0)
  70         {
  71           diff = 1;
  72           break;
  73         }
  74     }
  75
  76   s1[s1len - 1] = n1;
  77   s2[s2len - 1] = n2;
  78
  79 #else
  80
  81   diff = memcmp (s1, s2, s1len < s2len ? s1len : s2len);
  82   if (! diff)
  83     diff = s1len < s2len ? -1 : s1len != s2len;
  84   errno = 0;
  85
  86 #endif
  87
  88   return diff;
  89 }