1 bbcba3ed 2022-01-10 op /*	$OpenBSD: memmem.c,v 1.5 2020/04/16 12:39:28 claudio Exp $ */
  2 bbcba3ed 2022-01-10 op 
  3 bbcba3ed 2022-01-10 op /*
  4 bbcba3ed 2022-01-10 op  * Copyright (c) 2005-2020 Rich Felker, et al.
  5 bbcba3ed 2022-01-10 op  *
  6 bbcba3ed 2022-01-10 op  * Permission is hereby granted, free of charge, to any person obtaining
  7 bbcba3ed 2022-01-10 op  * a copy of this software and associated documentation files (the
  8 bbcba3ed 2022-01-10 op  * "Software"), to deal in the Software without restriction, including
  9 bbcba3ed 2022-01-10 op  * without limitation the rights to use, copy, modify, merge, publish,
 10 bbcba3ed 2022-01-10 op  * distribute, sublicense, and/or sell copies of the Software, and to
 11 bbcba3ed 2022-01-10 op  * permit persons to whom the Software is furnished to do so, subject to
 12 bbcba3ed 2022-01-10 op  * the following conditions:
 13 bbcba3ed 2022-01-10 op  *
 14 bbcba3ed 2022-01-10 op  * The above copyright notice and this permission notice shall be
 15 bbcba3ed 2022-01-10 op  * included in all copies or substantial portions of the Software.
 16 bbcba3ed 2022-01-10 op  *
 17 bbcba3ed 2022-01-10 op  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 18 bbcba3ed 2022-01-10 op  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 19 bbcba3ed 2022-01-10 op  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 20 bbcba3ed 2022-01-10 op  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 21 bbcba3ed 2022-01-10 op  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 22 bbcba3ed 2022-01-10 op  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 23 bbcba3ed 2022-01-10 op  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 24 bbcba3ed 2022-01-10 op  */
 25 bbcba3ed 2022-01-10 op 
 26 bbcba3ed 2022-01-10 op #include <string.h>
 27 bbcba3ed 2022-01-10 op #include <stdint.h>
 28 bbcba3ed 2022-01-10 op 
 29 bbcba3ed 2022-01-10 op static char *
 30 bbcba3ed 2022-01-10 op twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
 31 bbcba3ed 2022-01-10 op {
 32 bbcba3ed 2022-01-10 op 	uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1];
 33 bbcba3ed 2022-01-10 op 	for (h+=2, k-=2; k; k--, hw = hw<<8 | *h++)
 34 bbcba3ed 2022-01-10 op 		if (hw == nw) return (char *)h-2;
 35 bbcba3ed 2022-01-10 op 	return hw == nw ? (char *)h-2 : 0;
 36 bbcba3ed 2022-01-10 op }
 37 bbcba3ed 2022-01-10 op 
 38 bbcba3ed 2022-01-10 op static char *
 39 bbcba3ed 2022-01-10 op threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
 40 bbcba3ed 2022-01-10 op {
 41 bbcba3ed 2022-01-10 op 	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8;
 42 bbcba3ed 2022-01-10 op 	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8;
 43 bbcba3ed 2022-01-10 op 	for (h+=3, k-=3; k; k--, hw = (hw|*h++)<<8)
 44 bbcba3ed 2022-01-10 op 		if (hw == nw) return (char *)h-3;
 45 bbcba3ed 2022-01-10 op 	return hw == nw ? (char *)h-3 : 0;
 46 bbcba3ed 2022-01-10 op }
 47 bbcba3ed 2022-01-10 op 
 48 bbcba3ed 2022-01-10 op static char *
 49 bbcba3ed 2022-01-10 op fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n)
 50 bbcba3ed 2022-01-10 op {
 51 bbcba3ed 2022-01-10 op 	uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3];
 52 bbcba3ed 2022-01-10 op 	uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3];
 53 bbcba3ed 2022-01-10 op 	for (h+=4, k-=4; k; k--, hw = hw<<8 | *h++)
 54 bbcba3ed 2022-01-10 op 		if (hw == nw) return (char *)h-4;
 55 bbcba3ed 2022-01-10 op 	return hw == nw ? (char *)h-4 : 0;
 56 bbcba3ed 2022-01-10 op }
 57 bbcba3ed 2022-01-10 op 
 58 bbcba3ed 2022-01-10 op #define MAX(a,b) ((a)>(b)?(a):(b))
 59 bbcba3ed 2022-01-10 op #define MIN(a,b) ((a)<(b)?(a):(b))
 60 bbcba3ed 2022-01-10 op 
 61 bbcba3ed 2022-01-10 op #define BITOP(a,b,op) \
 62 bbcba3ed 2022-01-10 op  ((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
 63 bbcba3ed 2022-01-10 op 
 64 bbcba3ed 2022-01-10 op /*
 65 bbcba3ed 2022-01-10 op  * Maxime Crochemore and Dominique Perrin, Two-way string-matching,
 66 bbcba3ed 2022-01-10 op  * Journal of the ACM, 38(3):651-675, July 1991.
 67 bbcba3ed 2022-01-10 op  */
 68 bbcba3ed 2022-01-10 op static char *
 69 bbcba3ed 2022-01-10 op twoway_memmem(const unsigned char *h, const unsigned char *z,
 70 bbcba3ed 2022-01-10 op     const unsigned char *n, size_t l)
 71 bbcba3ed 2022-01-10 op {
 72 bbcba3ed 2022-01-10 op 	size_t i, ip, jp, k, p, ms, p0, mem, mem0;
 73 bbcba3ed 2022-01-10 op 	size_t byteset[32 / sizeof(size_t)] = { 0 };
 74 bbcba3ed 2022-01-10 op 	size_t shift[256];
 75 bbcba3ed 2022-01-10 op 
 76 bbcba3ed 2022-01-10 op 	/* Computing length of needle and fill shift table */
 77 bbcba3ed 2022-01-10 op 	for (i=0; i<l; i++)
 78 bbcba3ed 2022-01-10 op 		BITOP(byteset, n[i], |=), shift[n[i]] = i+1;
 79 bbcba3ed 2022-01-10 op 
 80 bbcba3ed 2022-01-10 op 	/* Compute maximal suffix */
 81 bbcba3ed 2022-01-10 op 	ip = -1; jp = 0; k = p = 1;
 82 bbcba3ed 2022-01-10 op 	while (jp+k<l) {
 83 bbcba3ed 2022-01-10 op 		if (n[ip+k] == n[jp+k]) {
 84 bbcba3ed 2022-01-10 op 			if (k == p) {
 85 bbcba3ed 2022-01-10 op 				jp += p;
 86 bbcba3ed 2022-01-10 op 				k = 1;
 87 bbcba3ed 2022-01-10 op 			} else k++;
 88 bbcba3ed 2022-01-10 op 		} else if (n[ip+k] > n[jp+k]) {
 89 bbcba3ed 2022-01-10 op 			jp += k;
 90 bbcba3ed 2022-01-10 op 			k = 1;
 91 bbcba3ed 2022-01-10 op 			p = jp - ip;
 92 bbcba3ed 2022-01-10 op 		} else {
 93 bbcba3ed 2022-01-10 op 			ip = jp++;
 94 bbcba3ed 2022-01-10 op 			k = p = 1;
 95 bbcba3ed 2022-01-10 op 		}
 96 bbcba3ed 2022-01-10 op 	}
 97 bbcba3ed 2022-01-10 op 	ms = ip;
 98 bbcba3ed 2022-01-10 op 	p0 = p;
 99 bbcba3ed 2022-01-10 op 
100 bbcba3ed 2022-01-10 op 	/* And with the opposite comparison */
101 bbcba3ed 2022-01-10 op 	ip = -1; jp = 0; k = p = 1;
102 bbcba3ed 2022-01-10 op 	while (jp+k<l) {
103 bbcba3ed 2022-01-10 op 		if (n[ip+k] == n[jp+k]) {
104 bbcba3ed 2022-01-10 op 			if (k == p) {
105 bbcba3ed 2022-01-10 op 				jp += p;
106 bbcba3ed 2022-01-10 op 				k = 1;
107 bbcba3ed 2022-01-10 op 			} else k++;
108 bbcba3ed 2022-01-10 op 		} else if (n[ip+k] < n[jp+k]) {
109 bbcba3ed 2022-01-10 op 			jp += k;
110 bbcba3ed 2022-01-10 op 			k = 1;
111 bbcba3ed 2022-01-10 op 			p = jp - ip;
112 bbcba3ed 2022-01-10 op 		} else {
113 bbcba3ed 2022-01-10 op 			ip = jp++;
114 bbcba3ed 2022-01-10 op 			k = p = 1;
115 bbcba3ed 2022-01-10 op 		}
116 bbcba3ed 2022-01-10 op 	}
117 bbcba3ed 2022-01-10 op 	if (ip+1 > ms+1) ms = ip;
118 bbcba3ed 2022-01-10 op 	else p = p0;
119 bbcba3ed 2022-01-10 op 
120 bbcba3ed 2022-01-10 op 	/* Periodic needle? */
121 bbcba3ed 2022-01-10 op 	if (memcmp(n, n+p, ms+1)) {
122 bbcba3ed 2022-01-10 op 		mem0 = 0;
123 bbcba3ed 2022-01-10 op 		p = MAX(ms, l-ms-1) + 1;
124 bbcba3ed 2022-01-10 op 	} else mem0 = l-p;
125 bbcba3ed 2022-01-10 op 	mem = 0;
126 bbcba3ed 2022-01-10 op 
127 bbcba3ed 2022-01-10 op 	/* Search loop */
128 bbcba3ed 2022-01-10 op 	for (;;) {
129 bbcba3ed 2022-01-10 op 		/* If remainder of haystack is shorter than needle, done */
130 bbcba3ed 2022-01-10 op 		if (z-h < l) return 0;
131 bbcba3ed 2022-01-10 op 
132 bbcba3ed 2022-01-10 op 		/* Check last byte first; advance by shift on mismatch */
133 bbcba3ed 2022-01-10 op 		if (BITOP(byteset, h[l-1], &)) {
134 bbcba3ed 2022-01-10 op 			k = l-shift[h[l-1]];
135 bbcba3ed 2022-01-10 op 			if (k) {
136 bbcba3ed 2022-01-10 op 				if (k < mem) k = mem;
137 bbcba3ed 2022-01-10 op 				h += k;
138 bbcba3ed 2022-01-10 op 				mem = 0;
139 bbcba3ed 2022-01-10 op 				continue;
140 bbcba3ed 2022-01-10 op 			}
141 bbcba3ed 2022-01-10 op 		} else {
142 bbcba3ed 2022-01-10 op 			h += l;
143 bbcba3ed 2022-01-10 op 			mem = 0;
144 bbcba3ed 2022-01-10 op 			continue;
145 bbcba3ed 2022-01-10 op 		}
146 bbcba3ed 2022-01-10 op 
147 bbcba3ed 2022-01-10 op 		/* Compare right half */
148 bbcba3ed 2022-01-10 op 		for (k=MAX(ms+1,mem); k<l && n[k] == h[k]; k++);
149 bbcba3ed 2022-01-10 op 		if (k < l) {
150 bbcba3ed 2022-01-10 op 			h += k-ms;
151 bbcba3ed 2022-01-10 op 			mem = 0;
152 bbcba3ed 2022-01-10 op 			continue;
153 bbcba3ed 2022-01-10 op 		}
154 bbcba3ed 2022-01-10 op 		/* Compare left half */
155 bbcba3ed 2022-01-10 op 		for (k=ms+1; k>mem && n[k-1] == h[k-1]; k--);
156 bbcba3ed 2022-01-10 op 		if (k <= mem) return (char *)h;
157 bbcba3ed 2022-01-10 op 		h += p;
158 bbcba3ed 2022-01-10 op 		mem = mem0;
159 bbcba3ed 2022-01-10 op 	}
160 bbcba3ed 2022-01-10 op }
161 bbcba3ed 2022-01-10 op 
162 bbcba3ed 2022-01-10 op void *
163 bbcba3ed 2022-01-10 op memmem(const void *h0, size_t k, const void *n0, size_t l)
164 bbcba3ed 2022-01-10 op {
165 bbcba3ed 2022-01-10 op 	const unsigned char *h = h0, *n = n0;
166 bbcba3ed 2022-01-10 op 
167 bbcba3ed 2022-01-10 op 	/* Return immediately on empty needle */
168 bbcba3ed 2022-01-10 op 	if (!l) return (void *)h;
169 bbcba3ed 2022-01-10 op 
170 bbcba3ed 2022-01-10 op 	/* Return immediately when needle is longer than haystack */
171 bbcba3ed 2022-01-10 op 	if (k<l) return 0;
172 bbcba3ed 2022-01-10 op 
173 bbcba3ed 2022-01-10 op 	/* Use faster algorithms for short needles */
174 bbcba3ed 2022-01-10 op 	h = memchr(h0, *n, k);
175 bbcba3ed 2022-01-10 op 	if (!h || l==1) return (void *)h;
176 bbcba3ed 2022-01-10 op 	k -= h - (const unsigned char *)h0;
177 bbcba3ed 2022-01-10 op 	if (k<l) return 0;
178 bbcba3ed 2022-01-10 op 	if (l==2) return twobyte_memmem(h, k, n);
179 bbcba3ed 2022-01-10 op 	if (l==3) return threebyte_memmem(h, k, n);
180 bbcba3ed 2022-01-10 op 	if (l==4) return fourbyte_memmem(h, k, n);
181 bbcba3ed 2022-01-10 op 
182 bbcba3ed 2022-01-10 op 	return twoway_memmem(h, h+k, n, l);
183 bbcba3ed 2022-01-10 op }