1 /* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2008 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <http://www.gnu.org/licenses/>. */
18 /* This particular implementation was written by Eric Blake, 2008. */
24 /* Specification of memmem. */
28 # define __builtin_expect(expr, val) (expr)
31 #define RETURN_TYPE void *
32 #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
33 #include "str-two-way.h"
37 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
38 if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
41 memmem (const void *haystack_start, size_t haystack_len,
42 const void *needle_start, size_t needle_len)
44 /* Abstract memory is considered to be an array of 'unsigned char' values,
45 not an array of 'char' values. See ISO C 99 section 6.2.6.1. */
46 const unsigned char *haystack = (const unsigned char *) haystack_start;
47 const unsigned char *needle = (const unsigned char *) needle_start;
50 /* The first occurrence of the empty string is deemed to occur at
51 the beginning of the string. */
52 return (void *) haystack;
54 /* Sanity check, otherwise the loop might search through the whole
56 if (__builtin_expect (haystack_len < needle_len, 0))
59 /* Use optimizations in memchr when possible, to reduce the search
60 size of haystack using a linear algorithm with a smaller
61 coefficient. However, avoid memchr for long needles, since we
62 can often achieve sublinear performance. */
63 if (needle_len < LONG_NEEDLE_THRESHOLD)
65 haystack = memchr (haystack, *needle, haystack_len);
66 if (!haystack || __builtin_expect (needle_len == 1, 0))
67 return (void *) haystack;
68 haystack_len -= haystack - (const unsigned char *) haystack_start;
69 if (haystack_len < needle_len)
71 return two_way_short_needle (haystack, haystack_len, needle, needle_len);
74 return two_way_long_needle (haystack, haystack_len, needle, needle_len);
77 #undef LONG_NEEDLE_THRESHOLD