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@ -1,57 +1,193 @@ |
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/* $OpenBSD: strstr.c,v 1.6 2015/08/31 02:53:57 guenther Exp $ */ |
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/*- |
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* Copyright (c) 1990 The Regents of the University of California. |
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* All rights reserved. |
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/* $OpenBSD: strstr.c,v 1.7 2017/04/12 16:06:12 millert Exp $ */ |
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/* |
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* Copyright (c) 2005-2014 Rich Felker |
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* |
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* This code is derived from software contributed to Berkeley by |
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* Chris Torek. |
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* Permission is hereby granted, free of charge, to any person obtaining |
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* a copy of this software and associated documentation files (the |
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* "Software"), to deal in the Software without restriction, including |
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* without limitation the rights to use, copy, modify, merge, publish, |
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* distribute, sublicense, and/or sell copies of the Software, and to |
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* permit persons to whom the Software is furnished to do so, subject to |
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* the following conditions: |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in the |
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* documentation and/or other materials provided with the distribution. |
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* 3. Neither the name of the University nor the names of its contributors |
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* may be used to endorse or promote products derived from this software |
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* without specific prior written permission. |
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* The above copyright notice and this permission notice shall be |
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* included in all copies or substantial portions of the Software. |
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* |
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. |
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY |
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, |
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE |
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. |
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*/ |
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#include <string.h> |
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#include <stdlib.h> |
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#include <stdint.h> |
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static char * |
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twobyte_strstr(const unsigned char *h, const unsigned char *n) |
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{ |
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uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1]; |
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for (h++; *h && hw != nw; hw = hw<<8 | *++h); |
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return *h ? (char *)h-1 : 0; |
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} |
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static char * |
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threebyte_strstr(const unsigned char *h, const unsigned char *n) |
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{ |
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uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8; |
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uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8; |
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for (h+=2; *h && hw != nw; hw = (hw|*++h)<<8); |
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return *h ? (char *)h-2 : 0; |
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} |
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static char * |
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fourbyte_strstr(const unsigned char *h, const unsigned char *n) |
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{ |
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uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3]; |
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uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3]; |
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for (h+=3; *h && hw != nw; hw = hw<<8 | *++h); |
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return *h ? (char *)h-3 : 0; |
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} |
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#define MAX(a,b) ((a)>(b)?(a):(b)) |
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#define MIN(a,b) ((a)<(b)?(a):(b)) |
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#define BITOP(a,b,op) \ |
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((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a)))) |
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/* |
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* Find the first occurrence of find in s. |
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* Maxime Crochemore and Dominique Perrin, Two-way string-matching, |
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* Journal of the ACM, 38(3):651-675, July 1991. |
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*/ |
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char * |
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strstr(const char *s, const char *find) |
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static char * |
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twoway_strstr(const unsigned char *h, const unsigned char *n) |
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{ |
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char c, sc; |
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size_t len; |
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if ((c = *find++) != 0) { |
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len = strlen(find); |
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do { |
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do { |
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if ((sc = *s++) == 0) |
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return (NULL); |
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} while (sc != c); |
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} while (strncmp(s, find, len) != 0); |
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s--; |
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const unsigned char *z; |
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size_t l, ip, jp, k, p, ms, p0, mem, mem0; |
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size_t byteset[32 / sizeof(size_t)] = { 0 }; |
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size_t shift[256]; |
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/* Computing length of needle and fill shift table */ |
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for (l=0; n[l] && h[l]; l++) |
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BITOP(byteset, n[l], |=), shift[n[l]] = l+1; |
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if (n[l]) return 0; /* hit the end of h */ |
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/* Compute maximal suffix */ |
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ip = -1; jp = 0; k = p = 1; |
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while (jp+k<l) { |
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if (n[ip+k] == n[jp+k]) { |
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if (k == p) { |
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jp += p; |
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k = 1; |
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} else k++; |
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} else if (n[ip+k] > n[jp+k]) { |
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jp += k; |
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k = 1; |
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p = jp - ip; |
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} else { |
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ip = jp++; |
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k = p = 1; |
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} |
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} |
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ms = ip; |
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p0 = p; |
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/* And with the opposite comparison */ |
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ip = -1; jp = 0; k = p = 1; |
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while (jp+k<l) { |
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if (n[ip+k] == n[jp+k]) { |
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if (k == p) { |
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jp += p; |
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k = 1; |
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} else k++; |
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} else if (n[ip+k] < n[jp+k]) { |
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jp += k; |
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k = 1; |
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p = jp - ip; |
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} else { |
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ip = jp++; |
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k = p = 1; |
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} |
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} |
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return ((char *)s); |
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if (ip+1 > ms+1) ms = ip; |
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else p = p0; |
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/* Periodic needle? */ |
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if (memcmp(n, n+p, ms+1)) { |
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mem0 = 0; |
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p = MAX(ms, l-ms-1) + 1; |
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} else mem0 = l-p; |
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mem = 0; |
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/* Initialize incremental end-of-haystack pointer */ |
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z = h; |
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/* Search loop */ |
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for (;;) { |
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/* Update incremental end-of-haystack pointer */ |
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if (z-h < l) { |
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/* Fast estimate for MIN(l,63) */ |
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size_t grow = l | 63; |
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const unsigned char *z2 = memchr(z, 0, grow); |
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if (z2) { |
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z = z2; |
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if (z-h < l) return 0; |
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} else z += grow; |
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} |
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/* Check last byte first; advance by shift on mismatch */ |
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if (BITOP(byteset, h[l-1], &)) { |
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k = l-shift[h[l-1]]; |
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#ifdef DEBUG |
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printf("adv by %zu (on %c) at [%s] (%zu;l=%zu)\n", k, h[l-1], h, shift[h[l-1]], l); |
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#endif |
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if (k) { |
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if (mem0 && mem && k < p) k = l-p; |
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h += k; |
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mem = 0; |
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continue; |
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} |
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} else { |
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h += l; |
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mem = 0; |
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continue; |
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} |
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/* Compare right half */ |
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for (k=MAX(ms+1,mem); n[k] && n[k] == h[k]; k++); |
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if (n[k]) { |
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h += k-ms; |
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mem = 0; |
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continue; |
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} |
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/* Compare left half */ |
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for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--); |
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if (k <= mem) return (char *)h; |
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h += p; |
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mem = mem0; |
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} |
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} |
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char * |
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strstr(const char *h, const char *n) |
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{ |
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/* Return immediately on empty needle */ |
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if (!n[0]) return (char *)h; |
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/* Use faster algorithms for short needles */ |
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h = strchr(h, *n); |
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if (!h || !n[1]) return (char *)h; |
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if (!h[1]) return 0; |
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if (!n[2]) return twobyte_strstr((void *)h, (void *)n); |
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if (!h[2]) return 0; |
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if (!n[3]) return threebyte_strstr((void *)h, (void *)n); |
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if (!h[3]) return 0; |
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if (!n[4]) return fourbyte_strstr((void *)h, (void *)n); |
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return twoway_strstr((void *)h, (void *)n); |
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} |
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DEF_STRONG(strstr); |