[C] source code - strcmp.c

/*
 * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
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 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1992, 1997 NeXT Software, Inc.  All rights reserved.
 * 
 *  File:   libc/gen/ppc/strcmp.c
 *
 *  This file contains machine dependent code for string comparison
 *  on NeXT 88K-based products.
 *
 * HISTORY
 *  24-Jan-1997 Umesh Vaishampayan (umeshv@NeXT.com)
 *  Ported to PPC.
 * 24-Nov-92  Derek B Clegg (dclegg@next.com)
 *  Created.
 */
#import <string.h>

/* This routine should be optimized. */

/* ANSI sez:
 *   The `strcmp' function compares the string pointed to by `s1' to the
 *   string pointed to by `s2'.
 *   The `strcmp' function returns an integer greater than, equal to, or less
 *   than zero, according as the string pointed to by `s1' is greater than,
 *   equal to, or less than the string pointed to by `s2'.  [4.11.4.2]
 */
int
strcmp(const char *s1, const char *s2)
{
    for ( ; *s1 == *s2; s1++, s2++)
    if (*s1 == '\0')
        return 0;
    return ((*(unsigned char *)s1 < *(unsigned char *)s2) ? -1 : +1);
}

Reference:

1. strcmp.c