From e93dc626f394c4c96bf63273158578a8c2540571 Mon Sep 17 00:00:00 2001 From: claudio <> Date: Thu, 16 Apr 2020 12:39:28 +0000 Subject: [PATCH] Replace the simple memmem() implementation with a version that is O(n) based on code from musl and now similar to our strstr(). OK tb@ millert@ --- src/lib/libc/string/memmem.c | 214 +++++++++++++++++++++++++++-------- 1 file changed, 167 insertions(+), 47 deletions(-) diff --git a/src/lib/libc/string/memmem.c b/src/lib/libc/string/memmem.c index 823443b0..3b180b4a 100644 --- a/src/lib/libc/string/memmem.c +++ b/src/lib/libc/string/memmem.c @@ -1,64 +1,184 @@ -/* $OpenBSD: memmem.c,v 1.4 2015/08/31 02:53:57 guenther Exp $ */ -/*- - * Copyright (c) 2005 Pascal Gloor +/* $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 +#include + +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. */ - -void * -memmem(const void *l, size_t l_len, const void *s, size_t s_len) +static char * +twoway_memmem(const unsigned char *h, const unsigned char *z, + const unsigned char *n, size_t l) { - const char *cur, *last; - const char *cl = l; - const char *cs = s; + 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 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 ms+1) ms = ip; + else p = p0; - /* a zero length needle should just return the haystack */ - if (s_len == 0) - return (void *)cl; + /* Periodic needle? */ + if (memcmp(n, n+p, ms+1)) { + mem0 = 0; + p = MAX(ms, l-ms-1) + 1; + } else mem0 = l-p; + mem = 0; - /* "s" must be smaller or equal to "l" */ - if (l_len < s_len) - return NULL; + /* 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); kmem && 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; - /* special case where s_len == 1 */ - if (s_len == 1) - return memchr(l, *cs, l_len); + /* Return immediately on empty needle */ + if (!l) return (void *)h; - /* the last position where its possible to find "s" in "l" */ - last = cl + l_len - s_len; + /* Return immediately when needle is longer than haystack */ + if (k