strstr.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
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, Version 1.0 only
6 * (the "License").  You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22/*
23 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
24 * Use is subject to license terms.
25 */
26
27#pragma ident	"%Z%%M%	%I%	%E% SMI"
28
29/*	Copyright (c) 1988 AT&T	*/
30/*	  All Rights Reserved  	*/
31
32
33#include "synonyms.h"
34#include <string.h>
35#include <stddef.h>
36#include <sys/types.h>
37
38/*
39 * strstr() locates the first occurrence in the string as1 of
40 * the sequence of characters (excluding the terminating null
41 * character) in the string as2. strstr() returns a pointer
42 * to the located string, or a null pointer if the string is
43 * not found. If as2 is "", the function returns as1.
44 */
45
46char *
47strstr(const char *as1, const char *as2)
48{
49	const char *s1, *s2;
50	const char *tptr;
51	char c;
52
53	s1 = as1;
54	s2 = as2;
55
56	if (s2 == NULL || *s2 == '\0')
57		return ((char *)s1);
58	c = *s2;
59
60	while (*s1)
61		if (*s1++ == c) {
62			tptr = s1;
63			while ((c = *++s2) == *s1++ && c)
64				;
65			if (c == 0)
66				return ((char *)tptr - 1);
67			s1 = tptr;
68			s2 = as2;
69			c = *s2;
70		}
71
72	return (NULL);
73}
74