1/* Return the offset of one string within another.
2 Copyright (C) 1994-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
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.
9
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.
14
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 <https://www.gnu.org/licenses/>. */
18
19/*
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 :-).
25 *
26 * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
27
28/* Specification. */
29#include <string.h>
30
31#include <ctype.h>
32#include <stdbool.h>
33#include <strings.h>
34
35#define TOLOWER(Ch) tolower (Ch)
36
37/* Two-Way algorithm. */
38#define RETURN_TYPE char *
39#define AVAILABLE(h, h_l, j, n_l) \
40 (((j) + (n_l) <= (h_l)) \
41 || ((h_l) += __strnlen ((void*)((h) + (h_l)), (n_l) + 512), \
42 (j) + (n_l) <= (h_l)))
43#define CHECK_EOL (1)
44#define RET0_IF_0(a) if (!a) goto ret0
45#define CANON_ELEMENT(c) TOLOWER (c)
46#define CMP_FUNC(p1, p2, l) \
47 __strncasecmp ((const char *) (p1), (const char *) (p2), l)
48#include "str-two-way.h"
49
50#undef strcasestr
51#undef __strcasestr
52
53#ifndef STRCASESTR
54#define STRCASESTR __strcasestr
55#endif
56
57
58/* Find the first occurrence of NEEDLE in HAYSTACK, using
59 case-insensitive comparison. This function gives unspecified
60 results in multibyte locales. */
61char *
62STRCASESTR (const char *haystack, const char *needle)
63{
64 size_t needle_len; /* Length of NEEDLE. */
65 size_t haystack_len; /* Known minimum length of HAYSTACK. */
66
67 /* Handle empty NEEDLE special case. */
68 if (needle[0] == '\0')
69 return (char *) haystack;
70
71 /* Ensure HAYSTACK length is at least as long as NEEDLE length.
72 Since a match may occur early on in a huge HAYSTACK, use strnlen
73 and read ahead a few cachelines for improved performance. */
74 needle_len = strlen (needle);
75 haystack_len = __strnlen (haystack, needle_len + 256);
76 if (haystack_len < needle_len)
77 return NULL;
78
79 /* Perform the search. Abstract memory is considered to be an array
80 of 'unsigned char' values, not an array of 'char' values. See
81 ISO C 99 section 6.2.6.1. */
82 if (needle_len < LONG_NEEDLE_THRESHOLD)
83 return two_way_short_needle ((const unsigned char *) haystack,
84 haystack_len,
85 (const unsigned char *) needle,
86 needle_len);
87 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
88 (const unsigned char *) needle,
89 needle_len);
90}
91
92#undef LONG_NEEDLE_THRESHOLD
93
94#ifndef NO_ALIAS
95weak_alias (__strcasestr, strcasestr)
96#endif
97