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* string/Makefile (distribute): Add str-two-way.h.

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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
This commit is contained in:
Ulrich Drepper 2008-05-15 04:42:20 +00:00
parent b194db7985
commit 0caca71ac9
9 changed files with 622 additions and 237 deletions
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15
ChangeLog
View file

@ -1,3 +1,16 @@
2008-05-14 Ulrich Drepper <drepper@redhat.com>
* string/Makefile (distribute): Add str-two-way.h.
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.
2008-04-11 Paolo Bonzini <bonzini@gnu.org>
* posix/regcomp.c (optimize_utf8): Add a note on why we test
@ -47,7 +60,7 @@
(match_prefix): Don't treat IPv4 loopback address special when
converting to v4 mapped addressed.
* sysdeps/posix/getaddrinfo.c (getaddrinfo): Add _res_hconf_init
* sysdeps/posix/getaddrinfo.c (getaddrinfo): Call _res_hconf_init
if necessary.
* posix/tst-rfc3484.c: Add dummy definition of _res_hconf_init.
* posix/tst-rfc3484-2.c: Likewise.

7
NEWS
View file

@ -15,6 +15,13 @@ Version 2.9
* getaddrinfo now handles DCCP and UDPlite.
Implemented by Ulrich Drepper.
* New fixed-size conversion macros: htobe16, htole16, be16toh, le16toh,
htobe32, htole32, be32toh, le32toh, htobe64, htole64, be64toh, le64toh.
Implemented by Ulrich Drepper.
* New implementation of memmem, strstr, and strcasestr which is O(n).
Implemented by Eric Blake.
Version 2.8

48
posix/regcomp.c
View file

@ -1038,7 +1038,9 @@ optimize_utf8 (re_dfa_t *dfa)
case BUF_LAST:
break;
default:
/* Word anchors etc. cannot be handled. */
/* Word anchors etc. cannot be handled. It's okay to test
opr.ctx_type since constraints (for all DFA nodes) are
created by ORing one or more opr.ctx_type values. */
return;
}
break;
@ -1318,6 +1320,8 @@ calc_first (void *extra, bin_tree_t *node)
node->node_idx = re_dfa_add_node (dfa, node->token);
if (BE (node->node_idx == -1, 0))
return REG_ESPACE;
if (node->token.type == ANCHOR)
dfa->nodes[node->node_idx].constraint = node->token.opr.ctx_type;
}
return REG_NOERROR;
}
@ -1446,22 +1450,17 @@ duplicate_node_closure (re_dfa_t *dfa, int top_org_node, int top_clone_node,
destination. */
org_dest = dfa->edests[org_node].elems[0];
re_node_set_empty (dfa->edests + clone_node);
if (dfa->nodes[org_node].type == ANCHOR)
/* If the node is root_node itself, it means the epsilon clsoure
has a loop. Then tie it to the destination of the root_node. */
if (org_node == root_node && clone_node != org_node)
{
/* In case of the node has another constraint, append it. */
if (org_node == root_node && clone_node != org_node)
{
/* ...but if the node is root_node itself, it means the
epsilon closure have a loop, then tie it to the
destination of the root_node. */
ret = re_node_set_insert (dfa->edests + clone_node,
org_dest);
if (BE (ret < 0, 0))
return REG_ESPACE;
break;
}
constraint |= dfa->nodes[org_node].opr.ctx_type;
ret = re_node_set_insert (dfa->edests + clone_node, org_dest);
if (BE (ret < 0, 0))
return REG_ESPACE;
break;
}
/* In case of the node has another constraint, add it. */
constraint |= dfa->nodes[org_node].constraint;
clone_dest = duplicate_node (dfa, org_dest, constraint);
if (BE (clone_dest == -1, 0))
return REG_ESPACE;
@ -1479,7 +1478,7 @@ duplicate_node_closure (re_dfa_t *dfa, int top_org_node, int top_clone_node,
clone_dest = search_duplicated_node (dfa, org_dest, constraint);
if (clone_dest == -1)
{
/* There are no such a duplicated node, create a new one. */
/* There is no such duplicated node, create a new one. */
reg_errcode_t err;
clone_dest = duplicate_node (dfa, org_dest, constraint);
if (BE (clone_dest == -1, 0))
@ -1494,7 +1493,7 @@ duplicate_node_closure (re_dfa_t *dfa, int top_org_node, int top_clone_node,
}
else
{
/* There are a duplicated node which satisfy the constraint,
/* There is a duplicated node which satisfies the constraint,
use it to avoid infinite loop. */
ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
if (BE (ret < 0, 0))
@ -1543,8 +1542,7 @@ duplicate_node (re_dfa_t *dfa, int org_idx, unsigned int constraint)
if (BE (dup_idx != -1, 1))
{
dfa->nodes[dup_idx].constraint = constraint;
if (dfa->nodes[org_idx].type == ANCHOR)
dfa->nodes[dup_idx].constraint |= dfa->nodes[org_idx].opr.ctx_type;
dfa->nodes[dup_idx].constraint |= dfa->nodes[org_idx].constraint;
dfa->nodes[dup_idx].duplicated = 1;
/* Store the index of the original node. */
@ -1624,7 +1622,6 @@ static reg_errcode_t
calc_eclosure_iter (re_node_set *new_set, re_dfa_t *dfa, int node, int root)
{
reg_errcode_t err;
unsigned int constraint;
int i, incomplete;
re_node_set eclosure;
incomplete = 0;
@ -1636,15 +1633,14 @@ calc_eclosure_iter (re_node_set *new_set, re_dfa_t *dfa, int node, int root)
We reference this value to avoid infinite loop. */
dfa->eclosures[node].nelem = -1;
constraint = ((dfa->nodes[node].type == ANCHOR)
? dfa->nodes[node].opr.ctx_type : 0);
/* If the current node has constraints, duplicate all nodes.
Since they must inherit the constraints. */
if (constraint
/* If the current node has constraints, duplicate all nodes
since they must inherit the constraints. */
if (dfa->nodes[node].constraint
&& dfa->edests[node].nelem
&& !dfa->nodes[dfa->edests[node].elems[0]].duplicated)
{
err = duplicate_node_closure (dfa, node, node, node, constraint);
err = duplicate_node_closure (dfa, node, node, node,
dfa->nodes[node].constraint);
if (BE (err != REG_NOERROR, 0))
return err;
}

6
posix/regex_internal.c
View file

@ -1665,11 +1665,9 @@ create_cd_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
for (i = 0 ; i < nodes->nelem ; i++)
{
unsigned int constraint = 0;
re_token_t *node = dfa->nodes + nodes->elems[i];
re_token_type_t type = node->type;
if (node->constraint)
constraint = node->constraint;
unsigned int constraint = node->constraint;
if (type == CHARACTER && !constraint)
continue;
@ -1682,8 +1680,6 @@ create_cd_newstate (const re_dfa_t *dfa, const re_node_set *nodes,
newstate->halt = 1;
else if (type == OP_BACK_REF)
newstate->has_backref = 1;
else if (type == ANCHOR)
constraint = node->opr.ctx_type;
if (constraint)
{

3
string/Makefile
View file

@ -55,7 +55,8 @@ tests := tester inl-tester noinl-tester testcopy test-ffs \
tst-strtok tst-strxfrm bug-strcoll1 tst-strfry \
bug-strtok1 $(addprefix test-,$(strop-tests)) \
bug-envz1 tst-strxfrm2 tst-endian
distribute := memcopy.h pagecopy.h tst-svc.expect test-string.h
distribute := memcopy.h pagecopy.h tst-svc.expect test-string.h \
str-two-way.h
include ../Rules

58
string/memmem.c
View file

@ -1,4 +1,4 @@
/* Copyright (C) 1991,92,93,94,96,97,98,2000,2004 Free Software Foundation, Inc.
/* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2008 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
@ -16,26 +16,36 @@
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <stddef.h>
/* This particular implementation was written by Eric Blake, 2008. */
#ifndef _LIBC
# include <config.h>
#endif
/* Specification of memmem. */
#include <string.h>
#ifndef _LIBC
# define __builtin_expect(expr, val) (expr)
#endif
#define RETURN_TYPE void *
#define AVAILABLE(h, h_l, j, n_l) ((j) <= (h_l) - (n_l))
#include "str-two-way.h"
#undef memmem
/* Return the first occurrence of NEEDLE in HAYSTACK. */
/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
if NEEDLE_LEN is 0, otherwise NULL if NEEDLE is not found in
HAYSTACK. */
void *
memmem (haystack, haystack_len, needle, needle_len)
const void *haystack;
size_t haystack_len;
const void *needle;
size_t needle_len;
memmem (const void *haystack_start, size_t haystack_len,
const void *needle_start, size_t needle_len)
{
const char *begin;
const char *const last_possible
= (const char *) haystack + haystack_len - needle_len;
/* 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. */
const unsigned char *haystack = (const unsigned char *) haystack_start;
const unsigned char *needle = (const unsigned char *) needle_start;
if (needle_len == 0)
/* The first occurrence of the empty string is deemed to occur at
@ -47,12 +57,22 @@ memmem (haystack, haystack_len, needle, needle_len)
if (__builtin_expect (haystack_len < needle_len, 0))
return NULL;
for (begin = (const char *) haystack; begin <= last_possible; ++begin)
if (begin[0] == ((const char *) needle)[0] &&
!memcmp ((const void *) &begin[1],
(const void *) ((const char *) needle + 1),
needle_len - 1))
return (void *) begin;
return NULL;
/* Use optimizations in memchr when possible, to reduce the search
size of haystack using a linear algorithm with a smaller
coefficient. However, avoid memchr for long needles, since we
can often achieve sublinear performance. */
if (needle_len < LONG_NEEDLE_THRESHOLD)
{
haystack = memchr (haystack, *needle, haystack_len);
if (!haystack || __builtin_expect (needle_len == 1, 0))
return (void *) haystack;
haystack_len -= haystack - (const unsigned char *) haystack_start;
if (haystack_len < needle_len)
return NULL;
return two_way_short_needle (haystack, haystack_len, needle, needle_len);
}
else
return two_way_long_needle (haystack, haystack_len, needle, needle_len);
}
#undef LONG_NEEDLE_THRESHOLD

430
string/str-two-way.h Normal file
View file

@ -0,0 +1,430 @@
/* Byte-wise substring search, using the Two-Way algorithm.
Copyright (C) 2008 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Written by Eric Blake <ebb9@byu.net>, 2008.
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. */
/* Before including this file, you need to include <string.h> (and
<config.h> before that, if not part of libc), and define:
RESULT_TYPE A macro that expands to the return type.
AVAILABLE(h, h_l, j, n_l)
A macro that returns nonzero if there are
at least N_L bytes left starting at H[J].
H is 'unsigned char *', H_L, J, and N_L
are 'size_t'; H_L is an lvalue. For
NUL-terminated searches, H_L can be
modified each iteration to avoid having
to compute the end of H up front.
For case-insensitivity, you may optionally define:
CMP_FUNC(p1, p2, l) A macro that returns 0 iff the first L
characters of P1 and P2 are equal.
CANON_ELEMENT(c) A macro that canonicalizes an element right after
it has been fetched from one of the two strings.
The argument is an 'unsigned char'; the result
must be an 'unsigned char' as well.
This file undefines the macros documented above, and defines
LONG_NEEDLE_THRESHOLD.
*/
#include <limits.h>
#include <stdint.h>
/* We use the Two-Way string matching algorithm, which guarantees
linear complexity with constant space. Additionally, for long
needles, we also use a bad character shift table similar to the
Boyer-Moore algorithm to achieve improved (potentially sub-linear)
performance.
See http://www-igm.univ-mlv.fr/~lecroq/string/node26.html#SECTION00260
and http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm
*/
/* Point at which computing a bad-byte shift table is likely to be
worthwhile. Small needles should not compute a table, since it
adds (1 << CHAR_BIT) + NEEDLE_LEN computations of preparation for a
speedup no greater than a factor of NEEDLE_LEN. The larger the
needle, the better the potential performance gain. On the other
hand, on non-POSIX systems with CHAR_BIT larger than eight, the
memory required for the table is prohibitive. */
#if CHAR_BIT < 10
# define LONG_NEEDLE_THRESHOLD 32U
#else
# define LONG_NEEDLE_THRESHOLD SIZE_MAX
#endif
#ifndef MAX
# define MAX(a, b) ((a < b) ? (b) : (a))
#endif
#ifndef CANON_ELEMENT
# define CANON_ELEMENT(c) c
#endif
#ifndef CMP_FUNC
# define CMP_FUNC memcmp
#endif
/* Perform a critical factorization of NEEDLE, of length NEEDLE_LEN.
Return the index of the first byte in the right half, and set
*PERIOD to the global period of the right half.
The global period of a string is the smallest index (possibly its
length) at which all remaining bytes in the string are repetitions
of the prefix (the last repetition may be a subset of the prefix).
When NEEDLE is factored into two halves, a local period is the
length of the smallest word that shares a suffix with the left half
and shares a prefix with the right half. All factorizations of a
non-empty NEEDLE have a local period of at least 1 and no greater
than NEEDLE_LEN.
A critical factorization has the property that the local period
equals the global period. All strings have at least one critical
factorization with the left half smaller than the global period.
Given an ordered alphabet, a critical factorization can be computed
in linear time, with 2 * NEEDLE_LEN comparisons, by computing the
larger of two ordered maximal suffixes. The ordered maximal
suffixes are determined by lexicographic comparison of
periodicity. */
static size_t
critical_factorization (const unsigned char *needle, size_t needle_len,
size_t *period)
{
/* Index of last byte of left half, or SIZE_MAX. */
size_t max_suffix, max_suffix_rev;
size_t j; /* Index into NEEDLE for current candidate suffix. */
size_t k; /* Offset into current period. */
size_t p; /* Intermediate period. */
unsigned char a, b; /* Current comparison bytes. */
/* Invariants:
0 <= j < NEEDLE_LEN - 1
-1 <= max_suffix{,_rev} < j (treating SIZE_MAX as if it were signed)
min(max_suffix, max_suffix_rev) < global period of NEEDLE
1 <= p <= global period of NEEDLE
p == global period of the substring NEEDLE[max_suffix{,_rev}+1...j]
1 <= k <= p
*/
/* Perform lexicographic search. */
max_suffix = SIZE_MAX;
j = 0;
k = p = 1;
while (j + k < needle_len)
{
a = CANON_ELEMENT (needle[j + k]);
b = CANON_ELEMENT (needle[max_suffix + k]);
if (a < b)
{
/* Suffix is smaller, period is entire prefix so far. */
j += k;
k = 1;
p = j - max_suffix;
}
else if (a == b)
{
/* Advance through repetition of the current period. */
if (k != p)
++k;
else
{
j += p;
k = 1;
}
}
else /* b < a */
{
/* Suffix is larger, start over from current location. */
max_suffix = j++;
k = p = 1;
}
}
*period = p;
/* Perform reverse lexicographic search. */
max_suffix_rev = SIZE_MAX;
j = 0;
k = p = 1;
while (j + k < needle_len)
{
a = CANON_ELEMENT (needle[j + k]);
b = CANON_ELEMENT (needle[max_suffix_rev + k]);
if (b < a)
{
/* Suffix is smaller, period is entire prefix so far. */
j += k;
k = 1;
p = j - max_suffix_rev;
}
else if (a == b)
{
/* Advance through repetition of the current period. */
if (k != p)
++k;
else
{
j += p;
k = 1;
}
}
else /* a < b */
{
/* Suffix is larger, start over from current location. */
max_suffix_rev = j++;
k = p = 1;
}
}
/* Choose the longer suffix. Return the first byte of the right
half, rather than the last byte of the left half. */
if (max_suffix_rev + 1 < max_suffix + 1)
return max_suffix + 1;
*period = p;
return max_suffix_rev + 1;
}
/* Return the first location of non-empty NEEDLE within HAYSTACK, or
NULL. HAYSTACK_LEN is the minimum known length of HAYSTACK. This
method is optimized for NEEDLE_LEN < LONG_NEEDLE_THRESHOLD.
Performance is guaranteed to be linear, with an initialization cost
of 2 * NEEDLE_LEN comparisons.
If AVAILABLE does not modify HAYSTACK_LEN (as in memmem), then at
most 2 * HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching.
If AVAILABLE modifies HAYSTACK_LEN (as in strstr), then at most 3 *
HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching. */
static RETURN_TYPE
two_way_short_needle (const unsigned char *haystack, size_t haystack_len,
const unsigned char *needle, size_t needle_len)
{
size_t i; /* Index into current byte of NEEDLE. */
size_t j; /* Index into current window of HAYSTACK. */
size_t period; /* The period of the right half of needle. */
size_t suffix; /* The index of the right half of needle. */
/* Factor the needle into two halves, such that the left half is
smaller than the global period, and the right half is
periodic (with a period as large as NEEDLE_LEN - suffix). */
suffix = critical_factorization (needle, needle_len, &period);
/* Perform the search. Each iteration compares the right half
first. */
if (CMP_FUNC (needle, needle + period, suffix) == 0)
{
/* Entire needle is periodic; a mismatch can only advance by the
period, so use memory to avoid rescanning known occurrences
of the period. */
size_t memory = 0;
j = 0;
while (AVAILABLE (haystack, haystack_len, j, needle_len))
{
/* Scan for matches in right half. */
i = MAX (suffix, memory);
while (i < needle_len && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
++i;
if (needle_len <= i)
{
/* Scan for matches in left half. */
i = suffix - 1;
while (memory < i + 1 && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
--i;
if (i + 1 < memory + 1)
return (RETURN_TYPE) (haystack + j);
/* No match, so remember how many repetitions of period
on the right half were scanned. */
j += period;
memory = needle_len - period;
}
else
{
j += i - suffix + 1;
memory = 0;
}
}
}
else
{
/* The two halves of needle are distinct; no extra memory is
required, and any mismatch results in a maximal shift. */
period = MAX (suffix, needle_len - suffix) + 1;
j = 0;
while (AVAILABLE (haystack, haystack_len, j, needle_len))
{
/* Scan for matches in right half. */
i = suffix;
while (i < needle_len && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
++i;
if (needle_len <= i)
{
/* Scan for matches in left half. */
i = suffix - 1;
while (i != SIZE_MAX && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
--i;
if (i == SIZE_MAX)
return (RETURN_TYPE) (haystack + j);
j += period;
}
else
j += i - suffix + 1;
}
}
return NULL;
}
/* Return the first location of non-empty NEEDLE within HAYSTACK, or
NULL. HAYSTACK_LEN is the minimum known length of HAYSTACK. This
method is optimized for LONG_NEEDLE_THRESHOLD <= NEEDLE_LEN.
Performance is guaranteed to be linear, with an initialization cost
of 3 * NEEDLE_LEN + (1 << CHAR_BIT) operations.
If AVAILABLE does not modify HAYSTACK_LEN (as in memmem), then at
most 2 * HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching,
and sublinear performance O(HAYSTACK_LEN / NEEDLE_LEN) is possible.
If AVAILABLE modifies HAYSTACK_LEN (as in strstr), then at most 3 *
HAYSTACK_LEN - NEEDLE_LEN comparisons occur in searching, and
sublinear performance is not possible. */
static RETURN_TYPE
two_way_long_needle (const unsigned char *haystack, size_t haystack_len,
const unsigned char *needle, size_t needle_len)
{
size_t i; /* Index into current byte of NEEDLE. */
size_t j; /* Index into current window of HAYSTACK. */
size_t period; /* The period of the right half of needle. */
size_t suffix; /* The index of the right half of needle. */
size_t shift_table[1U << CHAR_BIT]; /* See below. */
/* Factor the needle into two halves, such that the left half is
smaller than the global period, and the right half is
periodic (with a period as large as NEEDLE_LEN - suffix). */
suffix = critical_factorization (needle, needle_len, &period);
/* Populate shift_table. For each possible byte value c,
shift_table[c] is the distance from the last occurrence of c to
the end of NEEDLE, or NEEDLE_LEN if c is absent from the NEEDLE.
shift_table[NEEDLE[NEEDLE_LEN - 1]] contains the only 0. */
for (i = 0; i < 1U << CHAR_BIT; i++)
shift_table[i] = needle_len;
for (i = 0; i < needle_len; i++)
shift_table[CANON_ELEMENT (needle[i])] = needle_len - i - 1;
/* Perform the search. Each iteration compares the right half
first. */
if (CMP_FUNC (needle, needle + period, suffix) == 0)
{
/* Entire needle is periodic; a mismatch can only advance by the
period, so use memory to avoid rescanning known occurrences
of the period. */
size_t memory = 0;
size_t shift;
j = 0;
while (AVAILABLE (haystack, haystack_len, j, needle_len))
{
/* Check the last byte first; if it does not match, then
shift to the next possible match location. */
shift = shift_table[CANON_ELEMENT (haystack[j + needle_len - 1])];
if (0 < shift)
{
if (memory && shift < period)
{
/* Since needle is periodic, but the last period has
a byte out of place, there can be no match until
after the mismatch. */
shift = needle_len - period;
memory = 0;
}
j += shift;
continue;
}
/* Scan for matches in right half. The last byte has
already been matched, by virtue of the shift table. */
i = MAX (suffix, memory);
while (i < needle_len - 1 && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
++i;
if (needle_len - 1 <= i)
{
/* Scan for matches in left half. */
i = suffix - 1;
while (memory < i + 1 && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
--i;
if (i + 1 < memory + 1)
return (RETURN_TYPE) (haystack + j);
/* No match, so remember how many repetitions of period
on the right half were scanned. */
j += period;
memory = needle_len - period;
}
else
{
j += i - suffix + 1;
memory = 0;
}
}
}
else
{
/* The two halves of needle are distinct; no extra memory is
required, and any mismatch results in a maximal shift. */
size_t shift;
period = MAX (suffix, needle_len - suffix) + 1;
j = 0;
while (AVAILABLE (haystack, haystack_len, j, needle_len))
{
/* Check the last byte first; if it does not match, then
shift to the next possible match location. */
shift = shift_table[CANON_ELEMENT (haystack[j + needle_len - 1])];
if (0 < shift)
{
j += shift;
continue;
}
/* Scan for matches in right half. The last byte has
already been matched, by virtue of the shift table. */
i = suffix;
while (i < needle_len - 1 && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
++i;
if (needle_len - 1 <= i)
{
/* Scan for matches in left half. */
i = suffix - 1;
while (i != SIZE_MAX && (CANON_ELEMENT (needle[i])
== CANON_ELEMENT (haystack[i + j])))
--i;
if (i == SIZE_MAX)
return (RETURN_TYPE) (haystack + j);
j += period;
}
else
j += i - suffix + 1;
}
}
return NULL;
}
#undef AVAILABLE
#undef CANON_ELEMENT
#undef CMP_FUNC
#undef MAX
#undef RETURN_TYPE

150
string/strcasestr.c
View file

@ -1,5 +1,5 @@
/* Return the offset of one string within another.
Copyright (C) 1994, 1996-2000, 2004 Free Software Foundation, Inc.
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
@ -30,113 +30,71 @@
# include <config.h>
#endif
/* Specification. */
#include <string.h>
#include <ctype.h>
#include <stdbool.h>
#include <strings.h>
#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
#endif
#define TOLOWER(Ch) (isupper (Ch) ? tolower (Ch) : (Ch))
#ifdef _LIBC
# include <locale/localeinfo.h>
# define TOLOWER(c) __tolower_l ((unsigned char) c, loc)
#else
# define TOLOWER(c) _tolower (c)
#endif
typedef unsigned chartype;
/* 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 (phaystack, pneedle)
const char *phaystack;
const char *pneedle;
__strcasestr (const char *haystack_start, const char *needle_start)
{
register const unsigned char *haystack, *needle;
register chartype b, c;
#ifdef _LIBC
__locale_t loc = _NL_CURRENT_LOCALE;
#endif
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. */
haystack = (const unsigned char *) phaystack;
needle = (const unsigned char *) pneedle;
b = TOLOWER (*needle);
if (b != '\0')
/* 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)
{
haystack--; /* possible ANSI violation */
do
{
c = *++haystack;
if (c == '\0')
goto ret0;
}
while (TOLOWER (c) != (int) b);
c = TOLOWER (*++needle);
if (c == '\0')
goto foundneedle;
++needle;
goto jin;
for (;;)
{
register chartype a;
register const unsigned char *rhaystack, *rneedle;
do
{
a = *++haystack;
if (a == '\0')
goto ret0;
if (TOLOWER (a) == (int) b)
break;
a = *++haystack;
if (a == '\0')
goto ret0;
shloop:
;
}
while (TOLOWER (a) != (int) b);
jin: a = *++haystack;
if (a == '\0')
goto ret0;
if (TOLOWER (a) != (int) c)
goto shloop;
rhaystack = haystack-- + 1;
rneedle = needle;
a = TOLOWER (*rneedle);
if (TOLOWER (*rhaystack) == (int) a)
do
{
if (a == '\0')
goto foundneedle;
++rhaystack;
a = TOLOWER (*++needle);
if (TOLOWER (*rhaystack) != (int) a)
break;
if (a == '\0')
goto foundneedle;
++rhaystack;
a = TOLOWER (*++needle);
}
while (TOLOWER (*rhaystack) == (int) a);
needle = rneedle; /* took the register-poor approach */
if (a == '\0')
break;
}
ok &= (TOLOWER ((unsigned char) *haystack)
== TOLOWER ((unsigned char) *needle));
haystack++;
needle++;
}
foundneedle:
return (char*) haystack;
ret0:
return 0;
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)

142
string/strstr.c
View file

@ -1,5 +1,5 @@
/* Return the offset of one string within another.
Copyright (C) 1994,1996,1997,2000,2001,2003 Free Software Foundation, Inc.
Copyright (C) 1994,1996,1997,2000,2001,2003,2008 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
@ -17,107 +17,71 @@
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 */
/* This particular implementation was written by Eric Blake, 2008. */
#if HAVE_CONFIG_H
#ifndef _LIBC
# include <config.h>
#endif
#if defined _LIBC || defined HAVE_STRING_H
# include <string.h>
/* Specification of strstr. */
#include <string.h>
#include <stdbool.h>
#ifndef _LIBC
# define __builtin_expect(expr, val) (expr)
#endif
typedef unsigned chartype;
#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)))
#include "str-two-way.h"
#undef strstr
/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
HAYSTACK. */
char *
strstr (phaystack, pneedle)
const char *phaystack;
const char *pneedle;
strstr (const char *haystack_start, const char *needle_start)
{
const unsigned char *haystack, *needle;
chartype b;
const unsigned char *rneedle;
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. */
haystack = (const unsigned char *) phaystack;
/* 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 &= *haystack++ == *needle++;
if (*needle)
return NULL;
if (ok)
return (char *) haystack_start;
if ((b = *(needle = (const unsigned char *) pneedle)))
{
chartype c;
haystack--; /* possible ANSI violation */
/* Reduce the size of haystack using strchr, since it has a smaller
linear coefficient than the Two-Way algorithm. */
needle_len = needle - needle_start;
haystack = strchr (haystack_start + 1, *needle_start);
if (!haystack || __builtin_expect (needle_len == 1, 0))
return (char *) haystack;
needle -= needle_len;
haystack_len = (haystack > haystack_start + needle_len ? 1
: needle_len + haystack_start - haystack);
{
chartype a;
do
if (!(a = *++haystack))
goto ret0;
while (a != b);
}
if (!(c = *++needle))
goto foundneedle;
++needle;
goto jin;
for (;;)
{
{
chartype a;
if (0)
jin:{
if ((a = *++haystack) == c)
goto crest;
}
else
a = *++haystack;
do
{
for (; a != b; a = *++haystack)
{
if (!a)
goto ret0;
if ((a = *++haystack) == b)
break;
if (!a)
goto ret0;
}
}
while ((a = *++haystack) != c);
}
crest:
{
chartype a;
{
const unsigned char *rhaystack;
if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle)))
do
{
if (!a)
goto foundneedle;
if (*++rhaystack != (a = *++needle))
break;
if (!a)
goto foundneedle;
}
while (*++rhaystack == (a = *++needle));
needle = rneedle; /* took the register-poor aproach */
}
if (!a)
break;
}
}
}
foundneedle:
return (char *) haystack;
ret0:
return 0;
/* 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, needle_len);
return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
(const unsigned char *) needle, needle_len);
}
libc_hidden_builtin_def (strstr)
#undef LONG_NEEDLE_THRESHOLD