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head/lib/libc/string/memmem.c

/*- /*-
* Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com> * Copyright (c) 2005-2014 Rich Felker, et al.
* *
* Redistribution and use in source and binary forms, with or without * Permission is hereby granted, free of charge, to any person obtaining
* modification, are permitted provided that the following conditions * a copy of this software and associated documentation files (the
* are met: * "Software"), to deal in the Software without restriction, including
* 1. Redistributions of source code must retain the above copyright * without limitation the rights to use, copy, modify, merge, publish,
* notice, this list of conditions and the following disclaimer. * distribute, sublicense, and/or sell copies of the Software, and to
* 2. Redistributions in binary form must reproduce the above copyright * permit persons to whom the Software is furnished to do so, subject to
* notice, this list of conditions and the following disclaimer in the * the following conditions:
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
* *
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * The above copyright notice and this permission notice shall be
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * included in all copies or substantial portions of the Software.
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE *
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
* SUCH DAMAGE.
*/ */
#include <sys/cdefs.h> #include <sys/cdefs.h>
__FBSDID("$FreeBSD$"); __FBSDID("$FreeBSD$");
#include <string.h> #include <string.h>
#include <stdint.h>
/* static char *twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
* Find the first occurrence of the byte string s in byte string l. {
*/ uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
for (h++, k--; k; k--, hw = hw<<8 | *++h)
if (hw == nw) return (char *)h-1;
return 0;
}
void * static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
memmem(const void *l, size_t l_len, const void *s, size_t s_len)
{ {
register char *cur, *last; uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
const char *cl = (const char *)l; uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
const char *cs = (const char *)s; for (h+=2, k-=2; k; k--, hw = (hw|*++h)<<8)
if (hw == nw) return (char *)h-2;
return 0;
}
/* empty "s" matches the beginning of "l" */ static char *fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
if (s_len == 0) {
return (void *)cl; 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, k-=3; k; k--, hw = hw<<8 | *++h)
if (hw == nw) return (char *)h-3;
return 0;
}
/* "s" must be smaller or equal to "l" */ #define MAX(a,b) ((a)>(b)?(a):(b))
if (l_len < s_len) #define MIN(a,b) ((a)<(b)?(a):(b))
return NULL;
/* special case where s_len == 1 */ #define BITOP(a,b,op) \
if (s_len == 1) ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
return memchr(l, (int)*cs, l_len);
/* the last position where its possible to find "s" in "l" */ static char *twoway_memmem(const unsigned char *h, const unsigned char *z, const unsigned char *n, size_t l)
last = (char *)cl + l_len - s_len; {
size_t i, ip, jp, k, p, ms, p0, mem, mem0;
size_t byteset[32 / sizeof(size_t)] = { 0 };
size_t shift[256];
for (cur = (char *)cl; cur <= last; cur++) /* Computing length of needle and fill shift table */
if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0) for (i=0; i<l; i++)
return cur; BITOP(byteset, n[i], |=), shift[n[i]] = i+1;
return NULL; /* 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;
/* Search loop */
for (;;) {
/* If remainder of haystack is shorter than needle, done */
if (z-h < l) return 0;
/* Check last byte first; advance by shift on mismatch */
if (BITOP(byteset, h[l-1], &)) {
k = l-shift[h[l-1]];
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); k<l && n[k] == h[k]; k++);
if (k < l) {
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;
}
}
void *memmem(const void *h0, size_t k, const void *n0, size_t l)
{
const unsigned char *h = h0, *n = n0;
/* Return immediately on empty needle */
if (!l) return (void *)h;
/* Return immediately when needle is longer than haystack */
if (k<l) return 0;
/* Use faster algorithms for short needles */
h = memchr(h0, *n, k);
if (!h || l==1) return (void *)h;
k -= h - (const unsigned char *)h0;
if (k<l) return 0;
if (l==2) return twobyte_memmem(h, k, n);
if (l==3) return threebyte_memmem(h, k, n);
if (l==4) return fourbyte_memmem(h, k, n);
return twoway_memmem(h, h+k, n, l);
} }