lib/memcasecmp.c

   1 /* Case-insensitive buffer comparator.
   2    Copyright (C) 1996-1997, 2000, 2003, 2006, 2009-2018 Free Software
   3    Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #include <config.h>
  21
  22 #include "memcasecmp.h"
  23
  24 #include <ctype.h>
  25 #include <limits.h>
  26
  27 /* Like memcmp, but ignore differences in case.
  28    Convert to upper case (not lower) before comparing so that
  29    join -i works with sort -f.  */
  30
  31 int
  32 memcasecmp (const void *vs1, const void *vs2, size_t n)
  33 {
  34   size_t i;
  35   char const *s1 = vs1;
  36   char const *s2 = vs2;
  37   for (i = 0; i < n; i++)
  38     {
  39       unsigned char u1 = s1[i];
  40       unsigned char u2 = s2[i];
  41       int U1 = toupper (u1);
  42       int U2 = toupper (u2);
  43       int diff = (UCHAR_MAX <= INT_MAX ? U1 - U2
  44                   : U1 < U2 ? -1 : U2 < U1);
  45       if (diff)
  46         return diff;
  47     }
  48   return 0;
  49 }