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djm pushed a commit to branch master
in repository openssh.

commit eaf2765efe8bc74feba85c34295d067637fc6635
Author: Damien Miller <djm@mindrot.org>
Date: Mon Aug 10 13:24:09 2020 +1000

sync memmem.c with OpenBSD
---
openbsd-compat/memmem.c | 214 +++++++++++++++++++++++++++++++++++++-----------
1 file changed, 167 insertions(+), 47 deletions(-)

diff --git a/openbsd-compat/memmem.c b/openbsd-compat/memmem.c
index 3e5e6b5e..eb64eaab 100644
--- a/openbsd-compat/memmem.c
+++ b/openbsd-compat/memmem.c
@@ -1,30 +1,26 @@
-/* $OpenBSD: memmem.c,v 1.4 2015/08/31 02:53:57 guenther Exp $ */
-/*-
- * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
+/* $OpenBSD: memmem.c,v 1.5 2020/04/16 12:39:28 claudio Exp $ */
+
+/*
+ * Copyright (c) 2005-2020 Rich Felker, et al.
*
- * 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. The name of the author may not be used to endorse or promote
- * products derived from this software without specific prior written
- * permission.
+ * 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:
*
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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 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 "includes.h"
@@ -32,38 +28,162 @@
#ifndef HAVE_MEMMEM

#include <string.h>
+#include <stdint.h>
+
+static char *
+twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
+{
+ uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
+ for (h+=2, k-=2; k; k--, hw = hw<<8 | *h++)
+ if (hw == nw) return (char *)h-2;
+ return hw == nw ? (char *)h-2 : 0;
+}
+
+static char *
+threebyte_memmem(const unsigned char *h, size_t k, 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+=3, k-=3; k; k--, hw = (hw|*h++)<<8)
+ if (hw == nw) return (char *)h-3;
+ return hw == nw ? (char *)h-3 : 0;
+}
+
+static char *
+fourbyte_memmem(const unsigned char *h, size_t k, 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+=4, k-=4; k; k--, hw = hw<<8 | *h++)
+ if (hw == nw) return (char *)h-4;
+ return hw == nw ? (char *)h-4 : 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 the byte string s in byte string l.
+ * Maxime Crochemore and Dominique Perrin, Two-way string-matching,
+ * Journal of the ACM, 38(3):651-675, July 1991.
*/
+static char *
+twoway_memmem(const unsigned char *h, const unsigned char *z,
+ const unsigned char *n, size_t l)
+{
+ size_t i, 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 (i=0; i<l; i++)
+ BITOP(byteset, n[i], |=), shift[n[i]] = i+1;
+
+ /* 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 (k < mem) k = mem;
+ 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 *l, size_t l_len, const void *s, size_t s_len)
+memmem(const void *h0, size_t k, const void *n0, size_t l)
{
- const char *cur, *last;
- const char *cl = l;
- const char *cs = s;
+ const unsigned char *h = h0, *n = n0;

- /* a zero length needle should just return the haystack */
- if (s_len == 0)
- return (void *)cl;
+ /* Return immediately on empty needle */
+ if (!l) return (void *)h;

- /* "s" must be smaller or equal to "l" */
- if (l_len < s_len)
- return NULL;
+ /* Return immediately when needle is longer than haystack */
+ if (k<l) return 0;

- /* special case where s_len == 1 */
- if (s_len == 1)
- return memchr(l, *cs, l_len);
+ /* 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);

- /* the last position where its possible to find "s" in "l" */
- last = cl + l_len - s_len;
-
- for (cur = cl; cur <= last; cur++)
- if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
- return (void *)cur;
-
- return NULL;
+ return twoway_memmem(h, h+k, n, l);
}
DEF_WEAK(memmem);
#endif /* HAVE_MEMMEM */

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