-/* $OpenBSD: strstr.c,v 1.6 2015/08/31 02:53:57 guenther Exp $ */
-/*-
- * Copyright (c) 1990 The Regents of the University of California.
- * All rights reserved.
+/* $OpenBSD: strstr.c,v 1.7 2017/04/12 16:06:12 millert Exp $ */
+
+/*
+ * Copyright (c) 2005-2014 Rich Felker
*
- * This code is derived from software contributed to Berkeley by
- * Chris Torek.
+ * 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:
*
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * 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.
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
*
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * 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.
+ * 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 <string.h>
+#include <stdlib.h>
+#include <stdint.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 = n[0]<<24 | n[1]<<16 | n[2]<<8;
+ uint32_t hw = 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 = 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))))
/*
- * Find the first occurrence of find in s.
+ * Maxime Crochemore and Dominique Perrin, Two-way string-matching,
+ * Journal of the ACM, 38(3):651-675, July 1991.
*/
-char *
-strstr(const char *s, const char *find)
+static char *
+twoway_strstr(const unsigned char *h, const unsigned char *n)
{
- char c, sc;
- size_t len;
-
- if ((c = *find++) != 0) {
- len = strlen(find);
- do {
- do {
- if ((sc = *s++) == 0)
- return (NULL);
- } while (sc != c);
- } while (strncmp(s, find, len) != 0);
- s--;
+ 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;
+ }
}
- return ((char *)s);
+ 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]];
+#ifdef DEBUG
+ printf("adv by %zu (on %c) at [%s] (%zu;l=%zu)\n", k, h[l-1], h, shift[h[l-1]], l);
+#endif
+ 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);
}
DEF_STRONG(strstr);
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