/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* Copyright (c) 2005-2014 Rich Felker, et al.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <stdint.h>
#include <string.h>
static char *
twobyte_strstr(const unsigned char *h, const unsigned char *n)
{
uint16_t nw = n[0] << 8 | n[1], hw = h[0] << 8 | h[1];
for (h++; *h && hw != nw; hw = hw << 8 | *++h)
;
return *h ? (char *)h - 1 : 0;
}
static char *
threebyte_strstr(const unsigned char *h, const unsigned char *n)
{
uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8;
uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8;
for (h += 2; *h && hw != nw; hw = (hw | *++h) << 8)
;
return *h ? (char *)h - 2 : 0;
}
static char *
fourbyte_strstr(const unsigned char *h, const unsigned char *n)
{
uint32_t nw = (uint32_t)n[0] << 24 | n[1] << 16 | n[2] << 8 | n[3];
uint32_t hw = (uint32_t)h[0] << 24 | h[1] << 16 | h[2] << 8 | h[3];
for (h += 3; *h && hw != nw; hw = hw << 8 | *++h)
;
return *h ? (char *)h - 3 : 0;
}
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define BITOP(a, b, op) \
((a)[(size_t)(b) / (8 * sizeof *(a))] op \
(size_t)1 << ((size_t)(b) % (8 * sizeof *(a))))
/*
* Two Way string search algorithm, with a bad shift table applied to the last
* byte of the window. A bit array marks which entries in the shift table are
* initialized to avoid fully initializing a 1kb/2kb table.
*
* Reference: CROCHEMORE M., PERRIN D., 1991, Two-way string-matching,
* Journal of the ACM 38(3):651-675
*/
static char *
twoway_strstr(const unsigned char *h, const unsigned char *n)
{
const unsigned char *z;
size_t l, ip, jp, k, p, ms, p0, mem, mem0;
size_t byteset[32 / sizeof(size_t)] = { 0 };
size_t shift[256];
/* Computing length of needle and fill shift table */
for (l = 0; n[l] && h[l]; l++)
BITOP(byteset, n[l], |=), shift[n[l]] = l + 1;
if (n[l])
return 0; /* hit the end of h */
/* Compute maximal suffix */
ip = -1;
jp = 0;
k = p = 1;
while (jp + k < l) {
if (n[ip + k] == n[jp + k]) {
if (k == p) {
jp += p;
k = 1;
} else
k++;
} else if (n[ip + k] > n[jp + k]) {
jp += k;
k = 1;
p = jp - ip;
} else {
ip = jp++;
k = p = 1;
}
}
ms = ip;
p0 = p;
/* And with the opposite comparison */
ip = -1;
jp = 0;
k = p = 1;
while (jp + k < l) {
if (n[ip + k] == n[jp + k]) {
if (k == p) {
jp += p;
k = 1;
} else
k++;
} else if (n[ip + k] < n[jp + k]) {
jp += k;
k = 1;
p = jp - ip;
} else {
ip = jp++;
k = p = 1;
}
}
if (ip + 1 > ms + 1)
ms = ip;
else
p = p0;
/* Periodic needle? */
if (memcmp(n, n + p, ms + 1)) {
mem0 = 0;
p = MAX(ms, l - ms - 1) + 1;
} else
mem0 = l - p;
mem = 0;
/* Initialize incremental end-of-haystack pointer */
z = h;
/* Search loop */
for (;;) {
/* Update incremental end-of-haystack pointer */
if (z - h < l) {
/* Fast estimate for MIN(l,63) */
size_t grow = l | 63;
const unsigned char *z2 = memchr(z, 0, grow);
if (z2) {
z = z2;
if (z - h < l)
return 0;
} else
z += grow;
}
/* Check last byte first; advance by shift on mismatch */
if (BITOP(byteset, h[l - 1], &)) {
k = l - shift[h[l - 1]];
if (k) {
if (k < mem)
k = mem;
h += k;
mem = 0;
continue;
}
} else {
h += l;
mem = 0;
continue;
}
/* Compare right half */
for (k = MAX(ms + 1, mem); n[k] && n[k] == h[k]; k++)
;
if (n[k]) {
h += k - ms;
mem = 0;
continue;
}
/* Compare left half */
for (k = ms + 1; k > mem && n[k - 1] == h[k - 1]; k--)
;
if (k <= mem)
return (char *)h;
h += p;
mem = mem0;
}
}
char *
strstr(const char *h, const char *n)
{
/* Return immediately on empty needle */
if (!n[0])
return (char *)h;
/* Use faster algorithms for short needles */
h = strchr(h, *n);
if (!h || !n[1])
return (char *)h;
if (!h[1])
return 0;
if (!n[2])
return twobyte_strstr((void *)h, (void *)n);
if (!h[2])
return 0;
if (!n[3])
return threebyte_strstr((void *)h, (void *)n);
if (!h[3])
return 0;
if (!n[4])
return fourbyte_strstr((void *)h, (void *)n);
return twoway_strstr((void *)h, (void *)n);
}
