/* strncasecmp.c -- case insensitive string comparator

   Copyright (C) 1998-1999, 2005-2007, 2009-2020 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as published by

   the Free Software Foundation; either version 2.1, 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include <string.h>

#include <ctype.h>

#include <limits.h>

#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))

/* Compare no more than N bytes of strings S1 and S2, ignoring case,

   returning less than, equal to or greater than zero if S1 is

   lexicographically less than, equal to or greater than S2.

   Note: This function cannot work correctly in multibyte locales.  */

int

strncasecmp (const char *s1, const char *s2, size_t n)

{

  register const unsigned char *p1 = (const unsigned char *) s1;

  register const unsigned char *p2 = (const unsigned char *) s2;

  unsigned char c1, c2;

  if (p1 == p2 || n == 0)

    return 0;

  do

    {

      c1 = TOLOWER (*p1);

      c2 = TOLOWER (*p2);

      if (--n == 0 || c1 == '\0')

        break;

      ++p1;

      ++p2;

    }

  while (c1 == c2);

  if (UCHAR_MAX <= INT_MAX)

    return c1 - c2;

  else

    /* On machines where 'char' and 'int' are types of the same size, the

       difference of two 'unsigned char' values - including the sign bit -

       doesn't fit in an 'int'.  */

    return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);

}