xref: /illumos-gate/usr/src/lib/libc/port/gen/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 
46 char *
47 strstr(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