2005-08-25 18:26:58 +00:00
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/*-
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2017-11-25 17:12:48 +00:00
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* SPDX-License-Identifier: MIT
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*
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2017-03-18 00:51:39 +00:00
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* Copyright (c) 2005-2014 Rich Felker, et al.
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2005-08-25 18:26:58 +00:00
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*
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2017-03-18 00:51:39 +00:00
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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2005-08-25 18:26:58 +00:00
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*
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2017-03-18 00:51:39 +00:00
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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2005-08-25 18:26:58 +00:00
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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2017-03-18 00:51:39 +00:00
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#include <stdint.h>
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2020-11-18 22:01:34 +00:00
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#include <string.h>
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2005-08-25 18:26:58 +00:00
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2020-11-18 22:01:34 +00:00
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static char *
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twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
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2017-03-18 00:51:39 +00:00
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{
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2020-11-18 22:01:34 +00:00
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uint16_t nw = n[0] << 8 | n[1], hw = h[0] << 8 | h[1];
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for (h += 2, k -= 2; k; k--, hw = hw << 8 | *h++)
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if (hw == nw)
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return (char *)h - 2;
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return hw == nw ? (char *)h - 2 : 0;
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2017-03-18 00:51:39 +00:00
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}
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2005-08-25 18:26:58 +00:00
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2020-11-18 22:01:34 +00:00
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static char *
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threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
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2005-08-25 18:26:58 +00:00
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{
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2020-11-19 00:03:15 +00:00
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uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8;
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uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8;
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2020-11-18 22:01:34 +00:00
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for (h += 3, k -= 3; k; k--, hw = (hw | *h++) << 8)
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if (hw == nw)
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return (char *)h - 3;
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return hw == nw ? (char *)h - 3 : 0;
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2017-03-18 00:51:39 +00:00
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}
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2005-08-25 18:26:58 +00:00
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2020-11-18 22:01:34 +00:00
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static char *
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fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
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2017-03-18 00:51:39 +00:00
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{
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2020-11-19 00:03:15 +00:00
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uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8 | n[3];
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uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8 | h[3];
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2020-11-18 22:01:34 +00:00
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for (h += 4, k -= 4; k; k--, hw = hw << 8 | *h++)
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if (hw == nw)
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return (char *)h - 4;
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return hw == nw ? (char *)h - 4 : 0;
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2017-03-18 00:51:39 +00:00
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}
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2020-11-18 22:01:34 +00:00
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#define MAX(a, b) ((a) > (b) ? (a) : (b))
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#define MIN(a, b) ((a) < (b) ? (a) : (b))
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2005-08-25 18:26:58 +00:00
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2020-11-18 22:01:34 +00:00
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#define BITOP(a, b, op) \
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((a)[(size_t)(b) / (8 * sizeof *(a))] op \
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(size_t)1 << ((size_t)(b) % (8 * sizeof *(a))))
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2017-03-18 00:51:39 +00:00
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2017-03-18 00:53:24 +00:00
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/*
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* Two Way string search algorithm, with a bad shift table applied to the last
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* byte of the window. A bit array marks which entries in the shift table are
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* initialized to avoid fully initializing a 1kb/2kb table.
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*
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* Reference: CROCHEMORE M., PERRIN D., 1991, Two-way string-matching,
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* Journal of the ACM 38(3):651-675
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*/
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2020-11-18 22:01:34 +00:00
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static char *
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twoway_memmem(const unsigned char *h, const unsigned char *z,
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const unsigned char *n, size_t l)
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2017-03-18 00:51:39 +00:00
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{
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size_t i, ip, jp, k, p, ms, p0, mem, mem0;
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size_t byteset[32 / sizeof(size_t)] = { 0 };
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size_t shift[256];
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/* Computing length of needle and fill shift table */
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2020-11-18 22:01:34 +00:00
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for (i = 0; i < l; i++)
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BITOP(byteset, n[i], |=), shift[n[i]] = i + 1;
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2017-03-18 00:51:39 +00:00
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/* Compute maximal suffix */
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2020-11-18 22:01:34 +00:00
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ip = -1;
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jp = 0;
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k = p = 1;
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while (jp + k < l) {
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if (n[ip + k] == n[jp + k]) {
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2017-03-18 00:51:39 +00:00
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if (k == p) {
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jp += p;
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k = 1;
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2020-11-18 22:01:34 +00:00
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} else
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k++;
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} else if (n[ip + k] > n[jp + k]) {
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2017-03-18 00:51:39 +00:00
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jp += k;
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k = 1;
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p = jp - ip;
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} else {
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ip = jp++;
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k = p = 1;
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}
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}
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ms = ip;
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p0 = p;
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/* And with the opposite comparison */
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2020-11-18 22:01:34 +00:00
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ip = -1;
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jp = 0;
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k = p = 1;
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while (jp + k < l) {
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if (n[ip + k] == n[jp + k]) {
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2017-03-18 00:51:39 +00:00
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if (k == p) {
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jp += p;
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k = 1;
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2020-11-18 22:01:34 +00:00
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} else
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k++;
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} else if (n[ip + k] < n[jp + k]) {
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2017-03-18 00:51:39 +00:00
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jp += k;
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k = 1;
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p = jp - ip;
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} else {
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ip = jp++;
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k = p = 1;
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}
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}
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2020-11-18 22:01:34 +00:00
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if (ip + 1 > ms + 1)
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ms = ip;
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else
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p = p0;
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2017-03-18 00:51:39 +00:00
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/* Periodic needle? */
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2020-11-18 22:01:34 +00:00
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if (memcmp(n, n + p, ms + 1)) {
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2017-03-18 00:51:39 +00:00
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mem0 = 0;
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2020-11-18 22:01:34 +00:00
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p = MAX(ms, l - ms - 1) + 1;
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} else
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mem0 = l - p;
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2017-03-18 00:51:39 +00:00
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mem = 0;
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/* Search loop */
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for (;;) {
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/* If remainder of haystack is shorter than needle, done */
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2020-11-18 22:01:34 +00:00
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if (z - h < l)
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return 0;
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2017-03-18 00:51:39 +00:00
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/* Check last byte first; advance by shift on mismatch */
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2020-11-18 22:01:34 +00:00
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if (BITOP(byteset, h[l - 1], &)) {
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k = l - shift[h[l - 1]];
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2017-03-18 00:51:39 +00:00
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if (k) {
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2020-11-19 00:02:12 +00:00
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if (k < mem)
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k = mem;
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2017-03-18 00:51:39 +00:00
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h += k;
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mem = 0;
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continue;
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}
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} else {
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h += l;
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mem = 0;
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continue;
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}
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/* Compare right half */
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2020-11-18 22:01:34 +00:00
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for (k = MAX(ms + 1, mem); k < l && n[k] == h[k]; k++)
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;
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2017-03-18 00:51:39 +00:00
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if (k < l) {
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2020-11-18 22:01:34 +00:00
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h += k - ms;
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2017-03-18 00:51:39 +00:00
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mem = 0;
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continue;
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}
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/* Compare left half */
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2020-11-18 22:01:34 +00:00
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for (k = ms + 1; k > mem && n[k - 1] == h[k - 1]; k--)
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;
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if (k <= mem)
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return (char *)h;
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2017-03-18 00:51:39 +00:00
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h += p;
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mem = mem0;
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}
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}
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2020-11-18 22:01:34 +00:00
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void *
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memmem(const void *h0, size_t k, const void *n0, size_t l)
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2017-03-18 00:51:39 +00:00
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{
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const unsigned char *h = h0, *n = n0;
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2005-08-25 18:26:58 +00:00
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2017-03-18 00:51:39 +00:00
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/* Return immediately on empty needle */
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2020-11-18 22:01:34 +00:00
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if (!l)
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return (void *)h;
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2005-08-25 18:26:58 +00:00
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2017-03-18 00:51:39 +00:00
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/* Return immediately when needle is longer than haystack */
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2020-11-18 22:01:34 +00:00
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if (k < l)
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return 0;
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2005-08-25 18:26:58 +00:00
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2017-03-18 00:51:39 +00:00
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/* Use faster algorithms for short needles */
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h = memchr(h0, *n, k);
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2020-11-18 22:01:34 +00:00
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if (!h || l == 1)
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return (void *)h;
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2017-03-18 00:51:39 +00:00
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k -= h - (const unsigned char *)h0;
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2020-11-18 22:01:34 +00:00
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if (k < l)
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return 0;
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if (l == 2)
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return twobyte_memmem(h, k, n);
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if (l == 3)
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return threebyte_memmem(h, k, n);
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if (l == 4)
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return fourbyte_memmem(h, k, n);
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return twoway_memmem(h, h + k, n, l);
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2005-08-25 18:26:58 +00:00
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}
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