1 /* Return the offset of one string within another.
2 Copyright (C) 1994, 1996-2000, 2004, 2008, 2009, 2010
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
21 * My personal strstr() implementation that beats most other algorithms.
22 * Until someone tells me otherwise, I assume that this is the
23 * fastest implementation of strstr() in C.
24 * I deliberately chose not to comment it. You should have at least
25 * as much fun trying to understand it, as I had to write it :-).
27 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
40 #define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
42 /* Two-Way algorithm. */
43 #define RETURN_TYPE char *
44 #define AVAILABLE(h, h_l, j, n_l) \
45 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
46 && ((h_l) = (j) + (n_l)))
47 #define CANON_ELEMENT(c) TOLOWER (c)
48 #define CMP_FUNC(p1, p2, l) \
49 __strncasecmp ((const char *) (p1), (const char *) (p2), l)
50 #include "str-two-way.h"
56 #define STRCASESTR __strcasestr
60 /* Find the first occurrence of NEEDLE in HAYSTACK, using
61 case-insensitive comparison. This function gives unspecified
62 results in multibyte locales. */
64 STRCASESTR (const char *haystack_start
, const char *needle_start
)
66 const char *haystack
= haystack_start
;
67 const char *needle
= needle_start
;
68 size_t needle_len
; /* Length of NEEDLE. */
69 size_t haystack_len
; /* Known minimum length of HAYSTACK. */
70 bool ok
= true; /* True if NEEDLE is prefix of HAYSTACK. */
72 /* Determine length of NEEDLE, and in the process, make sure
73 HAYSTACK is at least as long (no point processing all of a long
74 NEEDLE if HAYSTACK is too short). */
75 while (*haystack
&& *needle
)
77 ok
&= (TOLOWER ((unsigned char) *haystack
)
78 == TOLOWER ((unsigned char) *needle
));
85 return (char *) haystack_start
;
86 needle_len
= needle
- needle_start
;
87 haystack
= haystack_start
+ 1;
88 haystack_len
= needle_len
- 1;
90 /* Perform the search. Abstract memory is considered to be an array
91 of 'unsigned char' values, not an array of 'char' values. See
92 ISO C 99 section 6.2.6.1. */
93 if (needle_len
< LONG_NEEDLE_THRESHOLD
)
94 return two_way_short_needle ((const unsigned char *) haystack
,
96 (const unsigned char *) needle_start
,
98 return two_way_long_needle ((const unsigned char *) haystack
, haystack_len
,
99 (const unsigned char *) needle_start
,
103 #undef LONG_NEEDLE_THRESHOLD
106 weak_alias (__strcasestr
, strcasestr
)