1  /* Case-insensitive buffer comparator.
       2     Copyright (C) 1996-1997, 2000, 2003, 2006, 2009-2023 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 : _GL_CMP (U1, U2));
      44        if (diff)
      45          return diff;
      46      }
      47    return 0;
      48  }