LibertyBSD_kernel/sys/lib/libkern/strncasecmp.c

/*	$OpenBSD: strncasecmp.c,v 1.6 2014/06/10 04:16:57 deraadt Exp $	*/

/*
 * Copyright (c) 1994 Christian E. Hopps
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by Christian E. Hopps.
 * 4. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

#include <lib/libkern/libkern.h>

int
strncasecmp(const char *s1, const char *s2, size_t n)
{
	if (n == 0)
		return 0;

	do {
		unsigned char c1 = (unsigned char) *s1++;
		unsigned char c2 = (unsigned char) *s2++;

		if (c1 != c2) {
			if (c1 >= 'A' && c1 <= 'Z' && 
			    c2 >= 'a' && c2 <= 'z')
				c1 += 'a' - 'A';
			else if (c1 >= 'a' && c1 <= 'z' && 
				 c2 >= 'A' && c2 <= 'Z')
				c2 += 'a' - 'A';
			if (c1 != c2)
				return c1 - c2;
		}
		if (c1 == 0)
			break;
	} while (--n != 0);

	return 0;
}