1/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2012 Free Software
2 Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation; either version 2.1, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public License along
16 with this program; if not, see <http://www.gnu.org/licenses/>. */
17
18/* This particular implementation was written by Eric Blake, 2008. */
19
20#ifndef _LIBC
21# include <config.h>
22#endif
23
24/* Specification of memmem. */
25#include <string.h>
26
27#ifndef _LIBC
28# define __builtin_expect(expr, val) (expr)
29#endif
30
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"
34
35/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
36 if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
37 HAYSTACK. */
38void *
39memmem (const void *haystack_start, size_t haystack_len,
40 const void *needle_start, size_t needle_len)
41{
42 /* Abstract memory is considered to be an array of 'unsigned char' values,
43 not an array of 'char' values. See ISO C 99 section 6.2.6.1. */
44 const unsigned char *haystack = (const unsigned char *) haystack_start;
45 const unsigned char *needle = (const unsigned char *) needle_start;
46
47 if (needle_len == 0)
48 /* The first occurrence of the empty string is deemed to occur at
49 the beginning of the string. */
50 return (void *) haystack;
51
52 /* Sanity check, otherwise the loop might search through the whole
53 memory. */
54 if (__builtin_expect (haystack_len < needle_len, 0))
55 return NULL;
56
57 /* Use optimizations in memchr when possible, to reduce the search
58 size of haystack using a linear algorithm with a smaller
59 coefficient. However, avoid memchr for long needles, since we
60 can often achieve sublinear performance. */
61 if (needle_len < LONG_NEEDLE_THRESHOLD)
62 {
63 haystack = memchr (haystack, *needle, haystack_len);
64 if (!haystack || __builtin_expect (needle_len == 1, 0))
65 return (void *) haystack;
66 haystack_len -= haystack - (const unsigned char *) haystack_start;
67 if (haystack_len < needle_len)
68 return NULL;
69 return two_way_short_needle (haystack, haystack_len, needle, needle_len);
70 }
71 else
72 return two_way_long_needle (haystack, haystack_len, needle, needle_len);
73}
74
75#undef LONG_NEEDLE_THRESHOLD
76