mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 21:23:52 +08:00
0caca71ac9
2008-03-29 Eric Blake <ebb9@byu.net> Rewrite string searches to O(n) rather than O(n^2). * string/str-two-way.h: New file. For linear fixed-allocation string searching. * string/memmem.c: New implementation. * string/strstr.c: New implementation. * string/strcasestr.c: New implementation. * sysdeps/posix/getaddrinfo.c (getaddrinfo): Call _res_hconf_init
101 lines
3.4 KiB
C
101 lines
3.4 KiB
C
/* Return the offset of one string within another.
|
|
Copyright (C) 1994, 1996-2000, 2004, 2008 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA. */
|
|
|
|
/*
|
|
* My personal strstr() implementation that beats most other algorithms.
|
|
* Until someone tells me otherwise, I assume that this is the
|
|
* fastest implementation of strstr() in C.
|
|
* I deliberately chose not to comment it. You should have at least
|
|
* as much fun trying to understand it, as I had to write it :-).
|
|
*
|
|
* Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */
|
|
|
|
#if HAVE_CONFIG_H
|
|
# include <config.h>
|
|
#endif
|
|
|
|
/* Specification. */
|
|
#include <string.h>
|
|
|
|
#include <ctype.h>
|
|
#include <stdbool.h>
|
|
#include <strings.h>
|
|
|
|
#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
|
|
|
|
/* Two-Way algorithm. */
|
|
#define RETURN_TYPE char *
|
|
#define AVAILABLE(h, h_l, j, n_l) \
|
|
(!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
|
|
&& ((h_l) = (j) + (n_l)))
|
|
#define CANON_ELEMENT(c) TOLOWER (c)
|
|
#define CMP_FUNC(p1, p2, l) \
|
|
strncasecmp ((const char *) (p1), (const char *) (p2), l)
|
|
#include "str-two-way.h"
|
|
|
|
#undef strcasestr
|
|
#undef __strcasestr
|
|
|
|
/* Find the first occurrence of NEEDLE in HAYSTACK, using
|
|
case-insensitive comparison. This function gives unspecified
|
|
results in multibyte locales. */
|
|
char *
|
|
__strcasestr (const char *haystack_start, const char *needle_start)
|
|
{
|
|
const char *haystack = haystack_start;
|
|
const char *needle = needle_start;
|
|
size_t needle_len; /* Length of NEEDLE. */
|
|
size_t haystack_len; /* Known minimum length of HAYSTACK. */
|
|
bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
|
|
|
|
/* Determine length of NEEDLE, and in the process, make sure
|
|
HAYSTACK is at least as long (no point processing all of a long
|
|
NEEDLE if HAYSTACK is too short). */
|
|
while (*haystack && *needle)
|
|
{
|
|
ok &= (TOLOWER ((unsigned char) *haystack)
|
|
== TOLOWER ((unsigned char) *needle));
|
|
haystack++;
|
|
needle++;
|
|
}
|
|
if (*needle)
|
|
return NULL;
|
|
if (ok)
|
|
return (char *) haystack_start;
|
|
needle_len = needle - needle_start;
|
|
haystack = haystack_start + 1;
|
|
haystack_len = needle_len - 1;
|
|
|
|
/* Perform the search. Abstract memory is considered to be an array
|
|
of 'unsigned char' values, not an array of 'char' values. See
|
|
ISO C 99 section 6.2.6.1. */
|
|
if (needle_len < LONG_NEEDLE_THRESHOLD)
|
|
return two_way_short_needle ((const unsigned char *) haystack,
|
|
haystack_len,
|
|
(const unsigned char *) needle_start,
|
|
needle_len);
|
|
return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
|
|
(const unsigned char *) needle_start,
|
|
needle_len);
|
|
}
|
|
|
|
#undef LONG_NEEDLE_THRESHOLD
|
|
|
|
weak_alias (__strcasestr, strcasestr)
|