1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
/* Return the offset of one string within another.
Copyright (C) 1994-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/*
* My personal strstr() implementation that beats most other algorithms.
* Until someone tells me otherwise, I assume that this is the
* fastest implementation of strstr() in C.
* I deliberately chose not to comment it. You should have at least
* as much fun trying to understand it, as I had to write it :-).
*
* Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
/* Specification. */
#include <string.h>
#include <ctype.h>
#include <stdbool.h>
#include <strings.h>
#define TOLOWER(Ch) tolower (Ch)
/* Two-Way algorithm. */
#define RETURN_TYPE char *
#define AVAILABLE(h, h_l, j, n_l) \
(((j) + (n_l) <= (h_l)) \
|| ((h_l) += __strnlen ((void*)((h) + (h_l)), (n_l) + 512), \
(j) + (n_l) <= (h_l)))
#define CHECK_EOL (1)
#define RET0_IF_0(a) if (!a) goto ret0
#define CANON_ELEMENT(c) TOLOWER (c)
#define CMP_FUNC(p1, p2, l) \
__strncasecmp ((const char *) (p1), (const char *) (p2), l)
#include "str-two-way.h"
#undef strcasestr
#undef __strcasestr
#ifndef STRCASESTR
#define STRCASESTR __strcasestr
#endif
/* Find the first occurrence of NEEDLE in HAYSTACK, using
case-insensitive comparison. This function gives unspecified
results in multibyte locales. */
char *
STRCASESTR (const char *haystack, const char *needle)
{
size_t needle_len; /* Length of NEEDLE. */
size_t haystack_len; /* Known minimum length of HAYSTACK. */
/* Handle empty NEEDLE special case. */
if (needle[0] == '\0')
return (char *) haystack;
/* Ensure HAYSTACK length is at least as long as NEEDLE length.
Since a match may occur early on in a huge HAYSTACK, use strnlen
and read ahead a few cachelines for improved performance. */
needle_len = strlen (needle);
haystack_len = __strnlen (haystack, needle_len + 256);
if (haystack_len < needle_len)
return NULL;
/* Perform the search. Abstract memory is considered to be an array
of 'unsigned char' values, not an array of 'char' values. See
ISO C 99 section 6.2.6.1. */
if (needle_len < LONG_NEEDLE_THRESHOLD)
return two_way_short_needle ((const unsigned char *) haystack,
haystack_len,
(const unsigned char *) needle,
needle_len);
return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
(const unsigned char *) needle,
needle_len);
}
#undef LONG_NEEDLE_THRESHOLD
#ifndef NO_ALIAS
weak_alias (__strcasestr, strcasestr)
#endif
|
