strstr.c revision 23a1ccea6aac035f084a7a4cdc968687d1b02daf
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 (c) 1989, 2010, Oracle and/or its affiliates. All rights reserved.
24 */
25
26/*	Copyright (c) 1988 AT&T	*/
27/*	  All Rights Reserved  	*/
28
29#include "lint.h"
30#include <string.h>
31#include <stddef.h>
32#include <sys/types.h>
33
34/*
35 * strstr() locates the first occurrence in the string as1 of
36 * the sequence of characters (excluding the terminating null
37 * character) in the string as2.  strstr() returns a pointer
38 * to the located string, or a null pointer if the string is
39 * not found.  If as2 is empty, the function returns as1.
40 */
41
42char *
43strstr(const char *as1, const char *as2)
44{
45	const char *s1, *s2;
46	const char *tptr;
47	char c;
48
49	s1 = as1;
50	s2 = as2;
51
52	if (s2 == NULL || *s2 == '\0')
53		return ((char *)s1);
54
55	c = *s2;
56	while (*s1 != '\0') {
57		if (c == *s1++) {
58			tptr = s1;
59			while ((c = *++s2) == *s1++ && c != '\0')
60				continue;
61			if (c == '\0')
62				return ((char *)tptr - 1);
63			s1 = tptr;
64			s2 = as2;
65			c = *s2;
66		}
67	}
68
69	return (NULL);
70}
71
72/*
73 * strnstr() locates the first occurrence in the string as1 of
74 * the sequence of characters (excluding the terminating null
75 * character) in the string as2, where not more than n characters
76 * from the string as1 are searched.  strnstr() returns a pointer
77 * to the located string, or a null pointer if the string is
78 * not found.  If as2 is empty, the function returns as1.
79 */
80
81char *
82strnstr(const char *as1, const char *as2, size_t n)
83{
84	const char *s1, *s2;
85	const char *tptr;
86	size_t k;
87	char c;
88
89	s1 = as1;
90	s2 = as2;
91
92	if (s2 == NULL || *s2 == '\0')
93		return ((char *)s1);
94
95	c = *s2;
96	while (*s1 != '\0' && n--) {
97		if (c == *s1++) {
98			k = n;
99			tptr = s1;
100			while ((c = *++s2) == *s1++ && c != '\0' && k--)
101				continue;
102			if (c == '\0')
103				return ((char *)tptr - 1);
104			s1 = tptr;
105			s2 = as2;
106			c = *s2;
107		}
108	}
109
110	return (NULL);
111}
112