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.
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 <http://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 (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
41 && ((h_l) = (j) + (n_l)))
42#define CHECK_EOL (1)
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"
48
49#undef strcasestr
50#undef __strcasestr
51
52#ifndef STRCASESTR
53#define STRCASESTR __strcasestr
54#endif
55
56
57/* Find the first occurrence of NEEDLE in HAYSTACK, using
58 case-insensitive comparison. This function gives unspecified
59 results in multibyte locales. */
60char *
61STRCASESTR (const char *haystack_start, const char *needle_start)
62{
63 const char *haystack = haystack_start;
64 const char *needle = needle_start;
65 size_t needle_len; /* Length of NEEDLE. */
66 size_t haystack_len; /* Known minimum length of HAYSTACK. */
67 bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
68
69 /* Determine length of NEEDLE, and in the process, make sure
70 HAYSTACK is at least as long (no point processing all of a long
71 NEEDLE if HAYSTACK is too short). */
72 while (*haystack && *needle)
73 {
74 ok &= (TOLOWER ((unsigned char) *haystack)
75 == TOLOWER ((unsigned char) *needle));
76 haystack++;
77 needle++;
78 }
79 if (*needle)
80 return NULL;
81 if (ok)
82 return (char *) haystack_start;
83 needle_len = needle - needle_start;
84 haystack = haystack_start + 1;
85 haystack_len = needle_len - 1;
86
87 /* Perform the search. Abstract memory is considered to be an array
88 of 'unsigned char' values, not an array of 'char' values. See
89 ISO C 99 section 6.2.6.1. */
90 if (needle_len < LONG_NEEDLE_THRESHOLD)
91 return two_way_short_needle ((const unsigned char *) haystack,
92 haystack_len,
93 (const unsigned char *) needle_start,
94 needle_len);
95 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
96 (const unsigned char *) needle_start,
97 needle_len);
98}
99
100#undef LONG_NEEDLE_THRESHOLD
101
102#ifndef NO_ALIAS
103weak_alias (__strcasestr, strcasestr)
104#endif
105