glibc/wcsmbs/wcsncmp.c

/* Copyright (C) 1995-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library 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 of the License, or (at your option) any later version.

   The GNU C Library 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 the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <wchar.h>

#ifndef WCSNCMP
# define WCSNCMP wcsncmp
#endif

/* Compare no more than N characters of S1 and S2,
   returning less than, equal to or greater than zero
   if S1 is lexicographically less than, equal to or
   greater than S2.  */
int
WCSNCMP (const wchar_t *s1, const wchar_t *s2, size_t n)
{
  wchar_t c1 = L'\0';
  wchar_t c2 = L'\0';

  if (n >= 4)
    {
      size_t n4 = n >> 2;
      do
	{
	  c1 = *s1++;
	  c2 = *s2++;
	  if (c1 == L'\0' || c1 != c2)
	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
	  c1 = *s1++;
	  c2 = *s2++;
	  if (c1 == L'\0' || c1 != c2)
	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
	  c1 = *s1++;
	  c2 = *s2++;
	  if (c1 == L'\0' || c1 != c2)
	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
	  c1 = *s1++;
	  c2 = *s2++;
	  if (c1 == L'\0' || c1 != c2)
	    return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
	} while (--n4 > 0);
      n &= 3;
    }

  while (n > 0)
    {
      c1 = *s1++;
      c2 = *s2++;
      if (c1 == L'\0' || c1 != c2)
	return c1 > c2 ? 1 : (c1 < c2 ? -1 : 0);
      n--;
    }

  return 0;
}