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head/lib/libc/string/strstr.c

/*- /*-
* Copyright (c) 1990, 1993 * Copyright (c) 2005-2014 Rich Felker, et al.
* The Regents of the University of California. All rights reserved.
* *
* This code is derived from software contributed to Berkeley by * Permission is hereby granted, free of charge, to any person obtaining
* Chris Torek. * 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:
* *
* Redistribution and use in source and binary forms, with or without * The above copyright notice and this permission notice shall be
* modification, are permitted provided that the following conditions * included in all copies or substantial portions of the Software.
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* *
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/ */
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)strstr.c 8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h> #include <sys/cdefs.h>
__FBSDID("$FreeBSD$"); __FBSDID("$FreeBSD$");
#include <string.h> #include <string.h>
#include <stdint.h>
/* static char *twobyte_strstr(const unsigned char *h, const unsigned char *n)
* Find the first occurrence of find in s.
*/
char *
strstr(const char *s, const char *find)
{ {
char c, sc; uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
size_t len; for (h++; *h && hw != nw; hw = hw<<8 | *++h);
return *h ? (char *)h-1 : 0;
}
if ((c = *find++) != '\0') { static char *threebyte_strstr(const unsigned char *h, const unsigned char *n)
len = strlen(find); {
do { uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
do { uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
if ((sc = *s++) == '\0') for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8);
return (NULL); return *h ? (char *)h-2 : 0;
} while (sc != c);
} while (strncmp(s, find, len) != 0);
s--;
} }
return ((char *)s);
static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
{
uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
uint32_t hw = 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))))
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]];
//printf("adv by %zu (on %c) at [%s] (%zu;l=%zu)\n", k, h[l-1], h, shift[h[l-1]], l);
if (k) {
if (mem0 && mem && k < p) k = l-p;
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);
} }