1 /* Searching in a string.
2 Copyright (C) 2005 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2005.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 #include <sys/cdefs.h>
19 __RCSID("$NetBSD: strstr.c,v 1.2 2016/05/17 14:00:09 christos Exp $");
20
21
22 #ifdef HAVE_CONFIG_H
23 # include <config.h>
24 #endif
25
26 /* Specification. */
27 #include "strstr.h"
28
29 #include <stddef.h> /* for NULL */
30
31 #if HAVE_MBRTOWC
32 # include "mbuiter.h"
33 #endif
34
35 /* Find the first occurrence of NEEDLE in HAYSTACK. */
36 char *
strstr(const char * haystack,const char * needle)37 strstr (const char *haystack, const char *needle)
38 {
39 /* Be careful not to look at the entire extent of haystack or needle
40 until needed. This is useful because of these two cases:
41 - haystack may be very long, and a match of needle found early,
42 - needle may be very long, and not even a short initial segment of
43 needle may be found in haystack. */
44 #if HAVE_MBRTOWC
45 if (MB_CUR_MAX > 1)
46 {
47 mbui_iterator_t iter_needle;
48
49 mbui_init (iter_needle, needle);
50 if (mbui_avail (iter_needle))
51 {
52 mbui_iterator_t iter_haystack;
53
54 mbui_init (iter_haystack, haystack);
55 for (;; mbui_advance (iter_haystack))
56 {
57 if (!mbui_avail (iter_haystack))
58 /* No match. */
59 return NULL;
60
61 if (mb_equal (mbui_cur (iter_haystack), mbui_cur (iter_needle)))
62 /* The first character matches. */
63 {
64 mbui_iterator_t rhaystack;
65 mbui_iterator_t rneedle;
66
67 memcpy (&rhaystack, &iter_haystack, sizeof (mbui_iterator_t));
68 mbui_advance (rhaystack);
69
70 mbui_init (rneedle, needle);
71 if (!mbui_avail (rneedle))
72 abort ();
73 mbui_advance (rneedle);
74
75 for (;; mbui_advance (rhaystack), mbui_advance (rneedle))
76 {
77 if (!mbui_avail (rneedle))
78 /* Found a match. */
79 return (char *) mbui_cur_ptr (iter_haystack);
80 if (!mbui_avail (rhaystack))
81 /* No match. */
82 return NULL;
83 if (!mb_equal (mbui_cur (rhaystack), mbui_cur (rneedle)))
84 /* Nothing in this round. */
85 break;
86 }
87 }
88 }
89 }
90 else
91 return (char *) haystack;
92 }
93 else
94 #endif
95 {
96 if (*needle != '\0')
97 {
98 /* Speed up the following searches of needle by caching its first
99 character. */
100 char b = *needle++;
101
102 for (;; haystack++)
103 {
104 if (*haystack == '\0')
105 /* No match. */
106 return NULL;
107 if (*haystack == b)
108 /* The first character matches. */
109 {
110 const char *rhaystack = haystack + 1;
111 const char *rneedle = needle;
112
113 for (;; rhaystack++, rneedle++)
114 {
115 if (*rneedle == '\0')
116 /* Found a match. */
117 return (char *) haystack;
118 if (*rhaystack == '\0')
119 /* No match. */
120 return NULL;
121 if (*rhaystack != *rneedle)
122 /* Nothing in this round. */
123 break;
124 }
125 }
126 }
127 }
128 else
129 return (char *) haystack;
130 }
131 }
132