strcasestr.c

来自「Newlib 嵌入式 C库 标准实现代码」· C语言 代码 · 共 99 行

/*
FUNCTION
	<<strcasestr>>---case-insensitive character string search
	
INDEX
	strcasestr

ANSI_SYNOPSIS
	#include <string.h>
	char *strcasestr(const char *<[s]>, const char *<[find]>);

TRAD_SYNOPSIS
	#include <string.h>
	int strcasecmp(<[s]>, <[find]>)
	char *<[s]>;
	char *<[find]>;

DESCRIPTION
	<<strcasestr>> searchs the string <[s]> for
	the first occurrence of the sequence <[find]>.  <<strcasestr>>
	is identical to <<strstr>> except the search is
	case-insensitive.

RETURNS 

	A pointer to the first case-insensitive occurrence of the sequence 
	<[find]> or <<NULL>> if no match was found.

PORTABILITY
<<strcasestr>> is in the Berkeley Software Distribution.

<<strcasestr>> requires no supporting OS subroutines. It uses
tolower() from elsewhere in this library.

QUICKREF
	strcasestr
*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 */

#include <sys/cdefs.h>

#include <ctype.h>
#include <string.h>

/*
 * Find the first occurrence of find in s, ignore case.
 */
char *
strcasestr(s, find)
	const char *s, *find;
{
	char c, sc;
	size_t len;

	if ((c = *find++) != 0) {
		c = tolower((unsigned char)c);
		len = strlen(find);
		do {
			do {
				if ((sc = *s++) == 0)
					return (NULL);
			} while ((char)tolower((unsigned char)sc) != c);
		} while (strncasecmp(s, find, len) != 0);
		s--;
	}
	return ((char *)s);
}