| /* $OpenBSD: strstr.c,v 1.8 2018/04/30 07:44:56 denis Exp $ */ |
| |
| /* |
| * Copyright (c) 2005-2014 Rich Felker |
| * |
| * 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 <string.h> |
| #include <stdlib.h> |
| #include <stdint.h> |
| |
| #ifdef DEBUG |
| #include <stdio.h> |
| #endif |
| |
| 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)))) |
| |
| /* |
| * Maxime Crochemore and Dominique Perrin, Two-way string-matching, |
| * Journal of the ACM, 38(3):651-675, July 1991. |
| */ |
| static char * |
| twoway_strstr(const unsigned char *h, const unsigned char *n) |
| { |
| 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; |
| } |
| } |
| 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); |