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/>. */
19 /* This particular implementation was written by Eric Blake, 2008. */
25 /* Specification of strstr. */
31 # define __builtin_expect(expr, val) (expr)
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)))
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"
50 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
51 if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
54 STRSTR (const char *haystack
, const char *needle
)
56 size_t needle_len
; /* Length of NEEDLE. */
57 size_t haystack_len
; /* Known minimum length of HAYSTACK. */
59 /* Handle empty NEEDLE special case. */
60 if (needle
[0] == '\0')
61 return (char *) haystack
;
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
;
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
)
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
;
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
,
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
);
91 libc_hidden_builtin_def (strstr
)
93 #undef LONG_NEEDLE_THRESHOLD