lib/libutils/isoc/newlib/strcmp.c

// SPDX-License-Identifier: BSD-3-Clause
/*
 * Copyright (c) 1994-2009  Red Hat, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the copyright holder nor the names of its
 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/* This file is copied from newlib-1.19 */

/*
FUNCTION
	<<strcmp>>---character string compare

INDEX
	strcmp

ANSI_SYNOPSIS
	#include <string.h>
	int strcmp(const char *<[a]>, const char *<[b]>);

TRAD_SYNOPSIS
	#include <string.h>
	int strcmp(<[a]>, <[b]>)
	char *<[a]>;
	char *<[b]>;

DESCRIPTION
	<<strcmp>> compares the string at <[a]> to
	the string at <[b]>.

RETURNS
	If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,
	<<strcmp>> returns a number greater than zero.  If the two
	strings match, <<strcmp>> returns zero.  If <<*<[a]>>>
	sorts lexicographically before <<*<[b]>>>, <<strcmp>> returns a
	number less than zero.

PORTABILITY
<<strcmp>> is ANSI C.

<<strcmp>> requires no supporting OS subroutines.

QUICKREF
	strcmp ansi pure
*/

#include "_ansi.h"
#include <string.h>
#include <limits.h>

/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
#define UNALIGNED(X, Y) \
	(((long)X & (sizeof(long) - 1)) | ((long)Y & (sizeof(long) - 1)))

/* DETECTNULL returns nonzero if (long)X contains a NULL byte. */
#if LONG_MAX == 2147483647L
#define DETECTNULL(X) (((X) - 0x01010101L) & ~(X) & 0x80808080UL)
#else
#if LONG_MAX == 9223372036854775807L
#define DETECTNULL(X) (((X) - 0x0101010101010101L) & ~(X) & \
		       0x8080808080808080UL)
#else
#error long int is not a 32bit or 64bit type.
#endif
#endif

#ifndef DETECTNULL
#error long int is not a 32bit or 64bit byte
#endif

int _DEFUN(strcmp, (s1, s2), _CONST char *s1 _AND _CONST char *s2)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
	while (*s1 != '\0' && *s1 == *s2) {
		s1++;
		s2++;
	}

	return (*(unsigned char *)s1) - (*(unsigned char *)s2);
#else
	unsigned long *a1;
	unsigned long *a2;

	/* If s1 or s2 are unaligned, then compare bytes. */
	if (!UNALIGNED(s1, s2)) {
		/*
		 * If s1 and s2 are word-aligned, compare them a word at a time.
		 */
		a1 = (unsigned long *)s1;
		a2 = (unsigned long *)s2;
		while (*a1 == *a2) {
			/*
			 * To get here, *a1 == *a2, thus if we find a null in
			 * *a1, then the strings must be equal, so return zero.
			 */
			if (DETECTNULL(*a1))
				return 0;

			a1++;
			a2++;
		}

		/*
		 * A difference was detected in last few bytes of s1, so search
		 * bytewise.
		 */
		s1 = (char *)a1;
		s2 = (char *)a2;
	}

	while (*s1 != '\0' && *s1 == *s2) {
		s1++;
		s2++;
	}
	return (*(unsigned char *)s1) - (*(unsigned char *)s2);
#endif /* not PREFER_SIZE_OVER_SPEED */
}