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<?php
/**
* Object caching using DBA backend.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Cache
*/
/**
* Cache that uses DBA as a backend.
* Slow due to the need to constantly open and close the file to avoid holding
* writer locks. Intended for development use only, as a memcached workalike
* for systems that don't have it.
*
* On construction you can pass array( 'dir' => '/some/path' ); as a parameter
* to override the default DBA files directory (wfTempDir()).
*
* @ingroup Cache
*/
class DBABagOStuff extends BagOStuff {
var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
/**
* @param $params array
*/
public function __construct( $params ) {
global $wgDBAhandler;
if ( !isset( $params['dir'] ) ) {
$params['dir'] = wfTempDir();
}
$this->mFile = $params['dir'] . '/mw-cache-' . wfWikiID() . '.db';
wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
$this->mHandler = $wgDBAhandler;
}
/**
* Encode value and expiry for storage
* @param $value
* @param $expiry
*
* @return string
*/
protected function encode( $value, $expiry ) {
# Convert to absolute time
$expiry = $this->convertExpiry( $expiry );
return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
}
/**
* @param $blob string
* @return array list containing value first and expiry second
*/
protected function decode( $blob ) {
if ( !is_string( $blob ) ) {
return array( false, 0 );
} else {
return array(
unserialize( substr( $blob, 11 ) ),
intval( substr( $blob, 0, 10 ) )
);
}
}
/**
* @return resource
*/
protected function getReader() {
if ( file_exists( $this->mFile ) ) {
$handle = dba_open( $this->mFile, 'rl', $this->mHandler );
} else {
$handle = $this->getWriter();
}
if ( !$handle ) {
wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
}
return $handle;
}
/**
* @return resource
*/
protected function getWriter() {
$handle = dba_open( $this->mFile, 'cl', $this->mHandler );
if ( !$handle ) {
wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
}
return $handle;
}
/**
* @param $key string
* @param $casToken[optional] mixed
* @return mixed
*/
public function get( $key, &$casToken = null ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$handle = $this->getReader();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
$val = dba_fetch( $key, $handle );
list( $val, $expiry ) = $this->decode( $val );
# Must close ASAP because locks are held
dba_close( $handle );
if ( $val !== false && $expiry && $expiry < time() ) {
# Key is expired, delete it
$handle = $this->getWriter();
dba_delete( $key, $handle );
dba_close( $handle );
wfDebug( __METHOD__ . ": $key expired\n" );
$val = false;
}
$casToken = $val;
wfProfileOut( __METHOD__ );
return $val;
}
/**
* @param $key string
* @param $value mixed
* @param $exptime int
* @return bool
*/
public function set( $key, $value, $exptime = 0 ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$blob = $this->encode( $value, $exptime );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
$ret = dba_replace( $key, $blob, $handle );
dba_close( $handle );
wfProfileOut( __METHOD__ );
return $ret;
}
/**
* @param $casToken mixed
* @param $key string
* @param $value mixed
* @param $exptime int
* @return bool
*/
public function cas( $casToken, $key, $value, $exptime = 0 ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$blob = $this->encode( $value, $exptime );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
// DBA is locked to any other write connection, so we can safely
// compare the current & previous value before saving new value
$val = dba_fetch( $key, $handle );
list( $val, $exptime ) = $this->decode( $val );
if ( $casToken !== $val ) {
dba_close( $handle );
wfProfileOut( __METHOD__ );
return false;
}
$ret = dba_replace( $key, $blob, $handle );
dba_close( $handle );
wfProfileOut( __METHOD__ );
return $ret;
}
/**
* @param $key string
* @param $time int
* @return bool
*/
public function delete( $key, $time = 0 ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
$ret = !dba_exists( $key, $handle ) || dba_delete( $key, $handle );
dba_close( $handle );
wfProfileOut( __METHOD__ );
return $ret;
}
/**
* @param $key string
* @param $value mixed
* @param $exptime int
* @return bool
*/
public function add( $key, $value, $exptime = 0 ) {
wfProfileIn( __METHOD__ );
$blob = $this->encode( $value, $exptime );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
$ret = dba_insert( $key, $blob, $handle );
# Insert failed, check to see if it failed due to an expired key
if ( !$ret ) {
list( , $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
if ( $expiry && $expiry < time() ) {
# Yes expired, delete and try again
dba_delete( $key, $handle );
$ret = dba_insert( $key, $blob, $handle );
# This time if it failed then it will be handled by the caller like any other race
}
}
dba_close( $handle );
wfProfileOut( __METHOD__ );
return $ret;
}
/**
* @param $key string
* @param $step integer
* @return integer|bool
*/
public function incr( $key, $step = 1 ) {
wfProfileIn( __METHOD__ );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
if ( $value !== false ) {
if ( $expiry && $expiry < time() ) {
# Key is expired, delete it
dba_delete( $key, $handle );
wfDebug( __METHOD__ . ": $key expired\n" );
$value = false;
} else {
$value += $step;
$blob = $this->encode( $value, $expiry );
$ret = dba_replace( $key, $blob, $handle );
$value = $ret ? $value : false;
}
}
dba_close( $handle );
wfProfileOut( __METHOD__ );
return ( $value === false ) ? false : (int)$value;
}
}
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