1 /* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007,2008,2009
2 Free Software Foundation, Inc.
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 2, 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, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
19 /* This particular implementation was written by Eric Blake, 2008. */
25 /* Specification of memmem. */
29 # define __builtin_expect(expr, val) (expr)
32 #define RETURN_TYPE void *
33 #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
34 #include "str-two-way.h"
36 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
37 if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
40 memmem (const void *haystack_start
, size_t haystack_len
,
41 const void *needle_start
, size_t needle_len
)
43 /* Abstract memory is considered to be an array of 'unsigned char' values,
44 not an array of 'char' values. See ISO C 99 section 6.2.6.1. */
45 const unsigned char *haystack
= (const unsigned char *) haystack_start
;
46 const unsigned char *needle
= (const unsigned char *) needle_start
;
49 /* The first occurrence of the empty string is deemed to occur at
50 the beginning of the string. */
51 return (void *) haystack
;
53 /* Sanity check, otherwise the loop might search through the whole
55 if (__builtin_expect (haystack_len
< needle_len
, 0))
58 /* Use optimizations in memchr when possible, to reduce the search
59 size of haystack using a linear algorithm with a smaller
60 coefficient. However, avoid memchr for long needles, since we
61 can often achieve sublinear performance. */
62 if (needle_len
< LONG_NEEDLE_THRESHOLD
)
64 haystack
= memchr (haystack
, *needle
, haystack_len
);
65 if (!haystack
|| __builtin_expect (needle_len
== 1, 0))
66 return (void *) haystack
;
67 haystack_len
-= haystack
- (const unsigned char *) haystack_start
;
68 if (haystack_len
< needle_len
)
70 return two_way_short_needle (haystack
, haystack_len
, needle
, needle_len
);
73 return two_way_long_needle (haystack
, haystack_len
, needle
, needle_len
);
76 #undef LONG_NEEDLE_THRESHOLD