diff --git a/src/lib/libc/string/strstr.c b/src/lib/libc/string/strstr.c index ccd08717..167d609c 100644 --- a/src/lib/libc/string/strstr.c +++ b/src/lib/libc/string/strstr.c @@ -1,57 +1,193 @@ -/* $OpenBSD: strstr.c,v 1.6 2015/08/31 02:53:57 guenther Exp $ */ -/*- - * Copyright (c) 1990 The Regents of the University of California. - * All rights reserved. +/* $OpenBSD: strstr.c,v 1.7 2017/04/12 16:06:12 millert Exp $ */ + +/* + * Copyright (c) 2005-2014 Rich Felker * - * This code is derived from software contributed to Berkeley by - * Chris Torek. + * 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: * - * 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. Neither the name of the University nor the names of its contributors - * may be used to endorse or promote products derived from this software - * without specific prior written permission. + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. * - * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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 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 +#include + +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)))) /* - * Find the first occurrence of find in s. + * Maxime Crochemore and Dominique Perrin, Two-way string-matching, + * Journal of the ACM, 38(3):651-675, July 1991. */ -char * -strstr(const char *s, const char *find) +static char * +twoway_strstr(const unsigned char *h, const unsigned char *n) { - char c, sc; - size_t len; - - if ((c = *find++) != 0) { - len = strlen(find); - do { - do { - if ((sc = *s++) == 0) - return (NULL); - } while (sc != c); - } while (strncmp(s, find, len) != 0); - s--; + 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 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; + + /* 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);