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 strstr. */
30 # define __builtin_expect(expr, val) (expr)
33 #define RETURN_TYPE char *
34 #define AVAILABLE(h, h_l, j, n_l) \
35 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
36 && ((h_l) = (j) + (n_l)))
37 #include "str-two-way.h"
39 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
40 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
43 strstr (const char *haystack_start
, const char *needle_start
)
45 const char *haystack
= haystack_start
;
46 const char *needle
= needle_start
;
47 size_t needle_len
; /* Length of NEEDLE. */
48 size_t haystack_len
; /* Known minimum length of HAYSTACK. */
49 bool ok
= true; /* True if NEEDLE is prefix of HAYSTACK. */
51 /* Determine length of NEEDLE, and in the process, make sure
52 HAYSTACK is at least as long (no point processing all of a long
53 NEEDLE if HAYSTACK is too short). */
54 while (*haystack
&& *needle
)
55 ok
&= *haystack
++ == *needle
++;
59 return (char *) haystack_start
;
61 /* Reduce the size of haystack using strchr, since it has a smaller
62 linear coefficient than the Two-Way algorithm. */
63 needle_len
= needle
- needle_start
;
64 haystack
= strchr (haystack_start
+ 1, *needle_start
);
65 if (!haystack
|| __builtin_expect (needle_len
== 1, 0))
66 return (char *) haystack
;
68 haystack_len
= (haystack
> haystack_start
+ needle_len
? 1
69 : needle_len
+ haystack_start
- haystack
);
71 /* Perform the search. Abstract memory is considered to be an array
72 of 'unsigned char' values, not an array of 'char' values. See
73 ISO C 99 section 6.2.6.1. */
74 if (needle_len
< LONG_NEEDLE_THRESHOLD
)
75 return two_way_short_needle ((const unsigned char *) haystack
,
77 (const unsigned char *) needle
, needle_len
);
78 return two_way_long_needle ((const unsigned char *) haystack
, haystack_len
,
79 (const unsigned char *) needle
, needle_len
);
82 #undef LONG_NEEDLE_THRESHOLD
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