strstr.c revision 7257d1b4d25bfac0c802847390e98a464fd787ac
1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27/*	Copyright (c) 1988 AT&T	*/
28/*	  All Rights Reserved  	*/
29
30#pragma ident	"%Z%%M%	%I%	%E% SMI"
31
32#include "lint.h"
33#include <string.h>
34#include <stddef.h>
35#include <sys/types.h>
36
37/*
38 * strstr() locates the first occurrence in the string as1 of
39 * the sequence of characters (excluding the terminating null
40 * character) in the string as2. strstr() returns a pointer
41 * to the located string, or a null pointer if the string is
42 * not found. If as2 is "", the function returns as1.
43 */
44
45char *
46strstr(const char *as1, const char *as2)
47{
48	const char *s1, *s2;
49	const char *tptr;
50	char c;
51
52	s1 = as1;
53	s2 = as2;
54
55	if (s2 == NULL || *s2 == '\0')
56		return ((char *)s1);
57	c = *s2;
58
59	while (*s1)
60		if (*s1++ == c) {
61			tptr = s1;
62			while ((c = *++s2) == *s1++ && c)
63				;
64			if (c == 0)
65				return ((char *)tptr - 1);
66			s1 = tptr;
67			s2 = as2;
68			c = *s2;
69		}
70
71	return (NULL);
72}
73