gsasl  1.10.0
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memmem.c
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1 /* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2021 Free Software
2  Foundation, Inc.
3  This file is part of the GNU C Library.
4 
5  This program is free software; you can redistribute it and/or modify
6  it under the terms of the GNU Lesser General Public License as published by
7  the Free Software Foundation; either version 2.1, or (at your option)
8  any later version.
9 
10  This program 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
13  GNU Lesser General Public License for more details.
14 
15  You should have received a copy of the GNU Lesser General Public License along
16  with this program; if not, see <https://www.gnu.org/licenses/>. */
17 
18 /* This particular implementation was written by Eric Blake, 2008. */
19 
20 #ifndef _LIBC
21 # include <config.h>
22 #endif
23 
24 /* Specification of memmem. */
25 #include <string.h>
26 
27 #define RETURN_TYPE void *
28 #define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
29 #include "str-two-way.h"
30 
31 /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
32  if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
33  HAYSTACK. */
34 void *
35 memmem (const void *haystack_start, size_t haystack_len,
36  const void *needle_start, size_t needle_len)
37 {
38  /* Abstract memory is considered to be an array of 'unsigned char' values,
39  not an array of 'char' values. See ISO C 99 section 6.2.6.1. */
40  const unsigned char *haystack = (const unsigned char *) haystack_start;
41  const unsigned char *needle = (const unsigned char *) needle_start;
42 
43  if (needle_len == 0)
44  /* The first occurrence of the empty string is deemed to occur at
45  the beginning of the string. */
46  return (void *) haystack;
47 
48  /* Sanity check, otherwise the loop might search through the whole
49  memory. */
50  if (__builtin_expect (haystack_len < needle_len, 0))
51  return NULL;
52 
53  /* Use optimizations in memchr when possible, to reduce the search
54  size of haystack using a linear algorithm with a smaller
55  coefficient. However, avoid memchr for long needles, since we
56  can often achieve sublinear performance. */
57  if (needle_len < LONG_NEEDLE_THRESHOLD)
58  {
59  haystack = memchr (haystack, *needle, haystack_len);
60  if (!haystack || __builtin_expect (needle_len == 1, 0))
61  return (void *) haystack;
62  haystack_len -= haystack - (const unsigned char *) haystack_start;
63  if (haystack_len < needle_len)
64  return NULL;
65  return two_way_short_needle (haystack, haystack_len, needle, needle_len);
66  }
67  else
68  return two_way_long_needle (haystack, haystack_len, needle, needle_len);
69 }
70 
71 #undef LONG_NEEDLE_THRESHOLD
void * memchr(void const *s, int c_in, size_t n)
Definition: memchr.c:59
#define NULL
Definition: stddef.in.h:72
void * memmem(const void *haystack_start, size_t haystack_len, const void *needle_start, size_t needle_len)
Definition: memmem.c:35
#define LONG_NEEDLE_THRESHOLD
Definition: str-two-way.h:65
static RETURN_TYPE two_way_short_needle(const unsigned char *haystack, size_t haystack_len, const unsigned char *needle, size_t needle_len)
Definition: str-two-way.h:235
static RETURN_TYPE two_way_long_needle(const unsigned char *haystack, size_t haystack_len, const unsigned char *needle, size_t needle_len)
Definition: str-two-way.h:329