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<?php
/**
* 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 (wgTmpDirectory).
*
* @ingroup Cache
*/
class DBABagOStuff extends BagOStuff {
var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
public function __construct( $params ) {
global $wgDBAhandler;
if ( !isset( $params['dir'] ) ) {
global $wgTmpDirectory;
$params['dir'] = $wgTmpDirectory;
}
$this->mFile = $params['dir']."/mw-cache-" . wfWikiID();
$this->mFile .= '.db';
wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
$this->mHandler = $wgDBAhandler;
}
/**
* Encode value and expiry for storage
* @param $value
* @param $expiry
*
* @return string
*/
function encode( $value, $expiry ) {
# Convert to absolute time
$expiry = $this->convertExpiry( $expiry );
return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
}
/**
* @return array list containing value first and expiry second
*/
function decode( $blob ) {
if ( !is_string( $blob ) ) {
return array( null, 0 );
} else {
return array(
unserialize( substr( $blob, 11 ) ),
intval( substr( $blob, 0, 10 ) )
);
}
}
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;
}
function getWriter() {
$handle = dba_open( $this->mFile, 'cl', $this->mHandler );
if ( !$handle ) {
wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
}
return $handle;
}
function get( $key ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$handle = $this->getReader();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return null;
}
$val = dba_fetch( $key, $handle );
list( $val, $expiry ) = $this->decode( $val );
# Must close ASAP because locks are held
dba_close( $handle );
if ( !is_null( $val ) && $expiry && $expiry < time() ) {
# Key is expired, delete it
$handle = $this->getWriter();
dba_delete( $key, $handle );
dba_close( $handle );
wfDebug( __METHOD__ . ": $key expired\n" );
$val = null;
}
wfProfileOut( __METHOD__ );
return $val;
}
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;
}
function delete( $key, $time = 0 ) {
wfProfileIn( __METHOD__ );
wfDebug( __METHOD__ . "($key)\n" );
$handle = $this->getWriter();
if ( !$handle ) {
wfProfileOut( __METHOD__ );
return false;
}
$ret = dba_delete( $key, $handle );
dba_close( $handle );
wfProfileOut( __METHOD__ );
return $ret;
}
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( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
if ( $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;
}
function keys() {
$reader = $this->getReader();
$k1 = dba_firstkey( $reader );
if ( !$k1 ) {
return array();
}
$result[] = $k1;
while ( $key = dba_nextkey( $reader ) ) {
$result[] = $key;
}
return $result;
}
}
|
