lib/memcoll.c

   1 /* Locale-specific memory comparison.
   2    Copyright 1999 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 #if HAVE_STRING_H
  25 # include <string.h>
  26 #endif
  27
  28 /* Compare S1 (with length S1LEN) and S2 (with length S2LEN) according
  29    to the LC_COLLATE locale.  S1 and S2 do not overlap, and are not
  30    adjacent.  Temporarily modify the bytes after S1 and S2, but
  31    restore their original contents before returning.  */
  32 int
  33 memcoll (char *s1, size_t s1len, char *s2, size_t s2len)
  34 {
  35   int diff;
  36   char n1 = s1[s1len];
  37   char n2 = s2[s2len];
  38
  39   s1[s1len++] = '\0';
  40   s2[s2len++] = '\0';
  41
  42   while (! (diff = strcoll (s1, s2)))
  43     {
  44       /* strcoll found no difference, but perhaps it was fooled by NUL
  45          characters in the data.  Work around this problem by advancing
  46          past the NUL chars.  */
  47       size_t size1 = strlen (s1) + 1;
  48       size_t size2 = strlen (s2) + 1;
  49       s1 += size1;
  50       s2 += size2;
  51       s1len -= size1;
  52       s2len -= size2;
  53
  54       if (s1len == 0)
  55         {
  56           if (s2len != 0)
  57             diff = -1;
  58           break;
  59         }
  60       else if (s2len == 0)
  61         {
  62           diff = 1;
  63           break;
  64         }
  65     }
  66
  67   s1[s1len - 1] = n1;
  68   s2[s2len - 1] = n2;
  69
  70   return diff;
  71 }