2 * SPDX-License-Identifier: MIT
4 * Copyright (c) 2005-2014 Rich Felker, et al.
6 * Permission is hereby granted, free of charge, to any person obtaining
7 * a copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sublicense, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
14 * The above copyright notice and this permission notice shall be
15 * included in all copies or substantial portions of the Software.
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
18 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
19 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
20 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
21 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
22 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
23 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 #include <sys/cdefs.h>
26 __FBSDID("$FreeBSD$");
32 twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
34 uint16_t nw = n[0] << 8 | n[1], hw = h[0] << 8 | h[1];
35 for (h += 2, k -= 2; k; k--, hw = hw << 8 | *h++)
38 return hw == nw ? (char *)h - 2 : 0;
42 threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
44 uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8;
45 uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8;
46 for (h += 3, k -= 3; k; k--, hw = (hw | *h++) << 8)
49 return hw == nw ? (char *)h - 3 : 0;
53 fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
55 uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8 | n[3];
56 uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8 | h[3];
57 for (h += 4, k -= 4; k; k--, hw = hw << 8 | *h++)
60 return hw == nw ? (char *)h - 4 : 0;
63 #define MAX(a, b) ((a) > (b) ? (a) : (b))
64 #define MIN(a, b) ((a) < (b) ? (a) : (b))
66 #define BITOP(a, b, op) \
67 ((a)[(size_t)(b) / (8 * sizeof *(a))] op \
68 (size_t)1 << ((size_t)(b) % (8 * sizeof *(a))))
71 * Two Way string search algorithm, with a bad shift table applied to the last
72 * byte of the window. A bit array marks which entries in the shift table are
73 * initialized to avoid fully initializing a 1kb/2kb table.
75 * Reference: CROCHEMORE M., PERRIN D., 1991, Two-way string-matching,
76 * Journal of the ACM 38(3):651-675
79 twoway_memmem(const unsigned char *h, const unsigned char *z,
80 const unsigned char *n, size_t l)
82 size_t i, ip, jp, k, p, ms, p0, mem, mem0;
83 size_t byteset[32 / sizeof(size_t)] = { 0 };
86 /* Computing length of needle and fill shift table */
87 for (i = 0; i < l; i++)
88 BITOP(byteset, n[i], |=), shift[n[i]] = i + 1;
90 /* Compute maximal suffix */
95 if (n[ip + k] == n[jp + k]) {
101 } else if (n[ip + k] > n[jp + k]) {
113 /* And with the opposite comparison */
118 if (n[ip + k] == n[jp + k]) {
124 } else if (n[ip + k] < n[jp + k]) {
138 /* Periodic needle? */
139 if (memcmp(n, n + p, ms + 1)) {
141 p = MAX(ms, l - ms - 1) + 1;
148 /* If remainder of haystack is shorter than needle, done */
152 /* Check last byte first; advance by shift on mismatch */
153 if (BITOP(byteset, h[l - 1], &)) {
154 k = l - shift[h[l - 1]];
168 /* Compare right half */
169 for (k = MAX(ms + 1, mem); k < l && n[k] == h[k]; k++)
176 /* Compare left half */
177 for (k = ms + 1; k > mem && n[k - 1] == h[k - 1]; k--)
187 memmem(const void *h0, size_t k, const void *n0, size_t l)
189 const unsigned char *h = h0, *n = n0;
191 /* Return immediately on empty needle */
195 /* Return immediately when needle is longer than haystack */
199 /* Use faster algorithms for short needles */
200 h = memchr(h0, *n, k);
203 k -= h - (const unsigned char *)h0;
207 return twobyte_memmem(h, k, n);
209 return threebyte_memmem(h, k, n);
211 return fourbyte_memmem(h, k, n);
213 return twoway_memmem(h, h + k, n, l);