coreutils/lib/memcasecmp.c

/* Case-insensitive buffer comparator.
   Copyright (C) 1996, 1997, 2000, 2003, 2006 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Jim Meyering.  */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "memcasecmp.h"

#include <ctype.h>
#include <limits.h>

/* Like memcmp, but ignore differences in case.
   Convert to upper case (not lower) before comparing so that
   join -i works with sort -f.  */

int
memcasecmp (const void *vs1, const void *vs2, size_t n)
{
  size_t i;
  char const *s1 = vs1;
  char const *s2 = vs2;
  for (i = 0; i < n; i++)
    {
      unsigned char u1 = s1[i];
      unsigned char u2 = s2[i];
      int U1 = toupper (u1);
      int U2 = toupper (u2);
      int diff = (UCHAR_MAX <= INT_MAX ? U1 - U2
		  : U1 < U2 ? -1 : U2 < U1);
      if (diff)
	return diff;
    }
  return 0;
}