1 /* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2012 Free Software
3 This file is part of the GNU C Library.
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
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 General Public License for more details.
15 You should have received a copy of the GNU General Public License along
16 with this program; if not, see <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"
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
39 memmem (const void *haystack_start
, size_t haystack_len
,
40 const void *needle_start
, size_t needle_len
)
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
;
48 /* The first occurrence of the empty string is deemed to occur at
49 the beginning of the string. */
50 return (void *) haystack
;
52 /* Sanity check, otherwise the loop might search through the whole
54 if (__builtin_expect (haystack_len
< needle_len
, 0))
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
)
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
)
69 return two_way_short_needle (haystack
, haystack_len
, needle
, needle_len
);
72 return two_way_long_needle (haystack
, haystack_len
, needle
, needle_len
);
75 #undef LONG_NEEDLE_THRESHOLD
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