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git.ipfire.org Git - thirdparty/glibc.git/blob - string/strcasestr.c
1 /* Return the offset of one string within another.
2 Copyright (C) 1994-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library 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 GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
20 * My personal strstr() implementation that beats most other algorithms.
21 * Until someone tells me otherwise, I assume that this is the
22 * fastest implementation of strstr() in C.
23 * I deliberately chose not to comment it. You should have at least
24 * as much fun trying to understand it, as I had to write it :-).
26 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
35 #define TOLOWER(Ch) tolower (Ch)
37 /* Two-Way algorithm. */
38 #define RETURN_TYPE char *
39 #define AVAILABLE(h, h_l, j, n_l) \
40 (((j) + (n_l) <= (h_l)) || ((h_l) += __strnlen ((void*)((h) + (h_l)), 512), \
41 (j) + (n_l) <= (h_l)))
43 #define RET0_IF_0(a) if (!a) goto ret0
44 #define CANON_ELEMENT(c) TOLOWER (c)
45 #define CMP_FUNC(p1, p2, l) \
46 __strncasecmp ((const char *) (p1), (const char *) (p2), l)
47 #include "str-two-way.h"
53 #define STRCASESTR __strcasestr
57 /* Find the first occurrence of NEEDLE in HAYSTACK, using
58 case-insensitive comparison. This function gives unspecified
59 results in multibyte locales. */
61 STRCASESTR (const char *haystack
, const char *needle
)
63 size_t needle_len
; /* Length of NEEDLE. */
64 size_t haystack_len
; /* Known minimum length of HAYSTACK. */
66 /* Handle empty NEEDLE special case. */
67 if (needle
[0] == '\0')
68 return (char *) haystack
;
70 /* Ensure HAYSTACK length is at least as long as NEEDLE length.
71 Since a match may occur early on in a huge HAYSTACK, use strnlen
72 and read ahead a few cachelines for improved performance. */
73 needle_len
= strlen (needle
);
74 haystack_len
= __strnlen (haystack
, needle_len
+ 256);
75 if (haystack_len
< needle_len
)
78 /* Perform the search. Abstract memory is considered to be an array
79 of 'unsigned char' values, not an array of 'char' values. See
80 ISO C 99 section 6.2.6.1. */
81 if (needle_len
< LONG_NEEDLE_THRESHOLD
)
82 return two_way_short_needle ((const unsigned char *) haystack
,
84 (const unsigned char *) needle
,
86 return two_way_long_needle ((const unsigned char *) haystack
, haystack_len
,
87 (const unsigned char *) needle
,
91 #undef LONG_NEEDLE_THRESHOLD
94 weak_alias (__strcasestr
, strcasestr
)