[src/trunk]: src/common/lib/libc/string switch to FreeBSD's memmem (faster)

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/bd8ab4f82a6d
branches:  trunk
changeset: 320447:bd8ab4f82a6d
user:      christos <christos%NetBSD.org@localhost>
date:      Sun Jul 08 17:53:12 2018 +0000

description:
switch to FreeBSD's memmem (faster)

diffstat:

 common/lib/libc/string/memmem.c |  191 ++++++++++++++++++++++++++++++++++++++++
 1 files changed, 191 insertions(+), 0 deletions(-)

diffs (195 lines):

diff -r cc31af9f4ee4 -r bd8ab4f82a6d common/lib/libc/string/memmem.c
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/common/lib/libc/string/memmem.c   Sun Jul 08 17:53:12 2018 +0000
@@ -0,0 +1,191 @@
+/*-
+ * 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>
+#if defined(LIBC_SCCS) && !defined(lint)
+#if 0
+__FBSDID("$FreeBSD: head/lib/libc/string/memmem.c 315468 2017-03-18 00:53:24Z emaste $");
+#else
+__RCSID("$NetBSD: memmem.c,v 1.1 2018/07/08 17:53:12 christos Exp $");
+#endif
+#endif /* LIBC_SCCS and not lint */
+
+#if !defined(_KERNEL) && !defined(_STANDALONE)
+#include <string.h>
+#include <stdint.h>
+#else
+#include <lib/libkern/libkern.h>
+#endif 
+
+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++, k--; k; k--, hw = hw<<8 | *++h)
+               if (hw == nw) return __UNCONST(h-1);
+       return 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+=2, k-=2; k; k--, hw = (hw|*++h)<<8)
+               if (hw == nw) return __UNCONST(h-2);
+       return 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+=3, k-=3; k; k--, hw = hw<<8 | *++h)
+               if (hw == nw) return __UNCONST(h-3);
+       return 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_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 = (size_t)-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 = (size_t)-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 ((size_t)(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 __UNCONST(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 __UNCONST(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 __UNCONST(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);
+}