strstr.c (d1d015864103b253b3fcb2f72a0da5b0cfeb31b6) strstr.c (88521634e964e3da78a0ce54109cddb59bf3f099)
1/*-
1/*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
2 * Copyright (c) 2005-2014 Rich Felker, et al.
4 *
3 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
7 *
11 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
19 *
14 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 */
22 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)strstr.c 8.1 (Berkeley) 6/4/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD$");
38
39#include <string.h>
23#include <sys/cdefs.h>
24__FBSDID("$FreeBSD$");
25
26#include <string.h>
27#include <stdint.h>
40
28
41/*
42 * Find the first occurrence of find in s.
43 */
44char *
45strstr(const char *s, const char *find)
29static char *twobyte_strstr(const unsigned char *h, const unsigned char *n)
46{
30{
47 char c, sc;
48 size_t len;
31 uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
32 for (h++; *h && hw != nw; hw = hw<<8 | *++h);
33 return *h ? (char *)h-1 : 0;
34}
49
35
50 if ((c = *find++) != '\0') {
51 len = strlen(find);
52 do {
53 do {
54 if ((sc = *s++) == '\0')
55 return (NULL);
56 } while (sc != c);
57 } while (strncmp(s, find, len) != 0);
58 s--;
36static char *threebyte_strstr(const unsigned char *h, const unsigned char *n)
37{
38 uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
39 uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
40 for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8);
41 return *h ? (char *)h-2 : 0;
42}
43
44static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
45{
46 uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
47 uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
48 for (h+=3; *h && hw != nw; hw = hw<<8 | *++h);
49 return *h ? (char *)h-3 : 0;
50}
51
52#define MAX(a,b) ((a)>(b)?(a):(b))
53#define MIN(a,b) ((a)<(b)?(a):(b))
54
55#define BITOP(a,b,op) \
56 ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
57
58static char *twoway_strstr(const unsigned char *h, const unsigned char *n)
59{
60 const unsigned char *z;
61 size_t l, ip, jp, k, p, ms, p0, mem, mem0;
62 size_t byteset[32 / sizeof(size_t)] = { 0 };
63 size_t shift[256];
64
65 /* Computing length of needle and fill shift table */
66 for (l=0; n[l] && h[l]; l++)
67 BITOP(byteset, n[l], |=), shift[n[l]] = l+1;
68 if (n[l]) return 0; /* hit the end of h */
69
70 /* Compute maximal suffix */
71 ip = -1; jp = 0; k = p = 1;
72 while (jp+k<l) {
73 if (n[ip+k] == n[jp+k]) {
74 if (k == p) {
75 jp += p;
76 k = 1;
77 } else k++;
78 } else if (n[ip+k] > n[jp+k]) {
79 jp += k;
80 k = 1;
81 p = jp - ip;
82 } else {
83 ip = jp++;
84 k = p = 1;
85 }
59 }
86 }
60 return ((char *)s);
87 ms = ip;
88 p0 = p;
89
90 /* And with the opposite comparison */
91 ip = -1; jp = 0; k = p = 1;
92 while (jp+k<l) {
93 if (n[ip+k] == n[jp+k]) {
94 if (k == p) {
95 jp += p;
96 k = 1;
97 } else k++;
98 } else if (n[ip+k] < n[jp+k]) {
99 jp += k;
100 k = 1;
101 p = jp - ip;
102 } else {
103 ip = jp++;
104 k = p = 1;
105 }
106 }
107 if (ip+1 > ms+1) ms = ip;
108 else p = p0;
109
110 /* Periodic needle? */
111 if (memcmp(n, n+p, ms+1)) {
112 mem0 = 0;
113 p = MAX(ms, l-ms-1) + 1;
114 } else mem0 = l-p;
115 mem = 0;
116
117 /* Initialize incremental end-of-haystack pointer */
118 z = h;
119
120 /* Search loop */
121 for (;;) {
122 /* Update incremental end-of-haystack pointer */
123 if (z-h < l) {
124 /* Fast estimate for MIN(l,63) */
125 size_t grow = l | 63;
126 const unsigned char *z2 = memchr(z, 0, grow);
127 if (z2) {
128 z = z2;
129 if (z-h < l) return 0;
130 } else z += grow;
131 }
132
133 /* Check last byte first; advance by shift on mismatch */
134 if (BITOP(byteset, h[l-1], &)) {
135 k = l-shift[h[l-1]];
136 //printf("adv by %zu (on %c) at [%s] (%zu;l=%zu)\n", k, h[l-1], h, shift[h[l-1]], l);
137 if (k) {
138 if (mem0 && mem && k < p) k = l-p;
139 h += k;
140 mem = 0;
141 continue;
142 }
143 } else {
144 h += l;
145 mem = 0;
146 continue;
147 }
148
149 /* Compare right half */
150 for (k=MAX(ms+1,mem); n[k] && n[k] == h[k]; k++);
151 if (n[k]) {
152 h += k-ms;
153 mem = 0;
154 continue;
155 }
156 /* Compare left half */
157 for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--);
158 if (k <= mem) return (char *)h;
159 h += p;
160 mem = mem0;
161 }
61}
162}
163
164char *strstr(const char *h, const char *n)
165{
166 /* Return immediately on empty needle */
167 if (!n[0]) return (char *)h;
168
169 /* Use faster algorithms for short needles */
170 h = strchr(h, *n);
171 if (!h || !n[1]) return (char *)h;
172 if (!h[1]) return 0;
173 if (!n[2]) return twobyte_strstr((void *)h, (void *)n);
174 if (!h[2]) return 0;
175 if (!n[3]) return threebyte_strstr((void *)h, (void *)n);
176 if (!h[3]) return 0;
177 if (!n[4]) return fourbyte_strstr((void *)h, (void *)n);
178
179 return twoway_strstr((void *)h, (void *)n);
180}