1/* Return the offset of one string within another.
2 Copyright (C) 1994-2019 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/* This particular implementation was written by Eric Blake, 2008. */
20
21#ifndef _LIBC
22# include <config.h>
23#endif
24
25/* Specification of strstr. */
26#include <string.h>
27
28#include <stdbool.h>
29
30#ifndef _LIBC
31# define __builtin_expect(expr, val) (expr)
32#endif
33
34#define RETURN_TYPE char *
35#define AVAILABLE(h, h_l, j, n_l) \
36 (((j) + (n_l) <= (h_l)) \
37 || ((h_l) += __strnlen ((void*)((h) + (h_l)), (n_l) + 512), \
38 (j) + (n_l) <= (h_l)))
39#define CHECK_EOL (1)
40#define RET0_IF_0(a) if (!a) goto ret0
41#define FASTSEARCH(S,C,N) (void*) strchr ((void*)(S), (C))
42#include "str-two-way.h"
43
44#undef strstr
45
46#ifndef STRSTR
47#define STRSTR strstr
48#endif
49
50/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
51 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
52 HAYSTACK. */
53char *
54STRSTR (const char *haystack, const char *needle)
55{
56 size_t needle_len; /* Length of NEEDLE. */
57 size_t haystack_len; /* Known minimum length of HAYSTACK. */
58
59 /* Handle empty NEEDLE special case. */
60 if (needle[0] == '\0')
61 return (char *) haystack;
62
63 /* Skip until we find the first matching char from NEEDLE. */
64 haystack = strchr (haystack, needle[0]);
65 if (haystack == NULL || needle[1] == '\0')
66 return (char *) haystack;
67
68 /* Ensure HAYSTACK length is at least as long as NEEDLE length.
69 Since a match may occur early on in a huge HAYSTACK, use strnlen
70 and read ahead a few cachelines for improved performance. */
71 needle_len = strlen (needle);
72 haystack_len = __strnlen (haystack, needle_len + 256);
73 if (haystack_len < needle_len)
74 return NULL;
75
76 /* Check whether we have a match. This improves performance since we avoid
77 the initialization overhead of the two-way algorithm. */
78 if (memcmp (haystack, needle, needle_len) == 0)
79 return (char *) haystack;
80
81 /* Perform the search. Abstract memory is considered to be an array
82 of 'unsigned char' values, not an array of 'char' values. See
83 ISO C 99 section 6.2.6.1. */
84 if (needle_len < LONG_NEEDLE_THRESHOLD)
85 return two_way_short_needle ((const unsigned char *) haystack,
86 haystack_len,
87 (const unsigned char *) needle, needle_len);
88 return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
89 (const unsigned char *) needle, needle_len);
90}
91libc_hidden_builtin_def (strstr)
92
93#undef LONG_NEEDLE_THRESHOLD
94