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<?php
/**
* Cache of file objects, wrapping some RepoGroup functions to avoid redundant
* queries. Loosely inspired by the LinkCache / LinkBatch classes for titles.
*
* ISSUE: Merge with RepoGroup?
*
* @ingroup FileRepo
*/
class FileCache {
var $repoGroup;
var $cache = array(), $notFound = array();
protected static $instance;
/**
* Get a FileCache instance. Typically, only one instance of FileCache
* is needed in a MediaWiki invocation.
*/
static function singleton() {
if ( self::$instance ) {
return self::$instance;
}
self::$instance = new FileCache( RepoGroup::singleton() );
return self::$instance;
}
/**
* Destroy the singleton instance, so that a new one will be created next
* time singleton() is called.
*/
static function destroySingleton() {
self::$instance = null;
}
/**
* Set the singleton instance to a given object
*/
static function setSingleton( $instance ) {
self::$instance = $instance;
}
/**
* Construct a group of file repositories.
* @param RepoGroup $repoGroup
*/
function __construct( $repoGroup ) {
$this->repoGroup = $repoGroup;
}
/**
* Add some files to the cache. This is a fairly low-level function,
* which most users should not need to call. Note that any existing
* entries for the same keys will not be replaced. Call clearFiles()
* first if you need that.
* @param array $files array of File objects, indexed by DB key
*/
function addFiles( $files ) {
wfDebug( "FileCache adding ".count( $files )." files\n" );
$this->cache += $files;
}
/**
* Remove some files from the cache, so that their existence will be
* rechecked. This is a fairly low-level function, which most users
* should not need to call.
* @param array $remove array indexed by DB keys to remove (the values are ignored)
*/
function clearFiles( $remove ) {
wfDebug( "FileCache clearing data for ".count( $remove )." files\n" );
$this->cache = array_diff_keys( $this->cache, $remove );
$this->notFound = array_diff_keys( $this->notFound, $remove );
}
/**
* Mark some DB keys as nonexistent. This is a fairly low-level
* function, which most users should not need to call.
* @param array $dbkeys array of DB keys
*/
function markNotFound( $dbkeys ) {
wfDebug( "FileCache marking ".count( $dbkeys )." files as not found\n" );
$this->notFound += array_fill_keys( $dbkeys, true );
}
/**
* Search the cache for a file.
* @param mixed $title Title object or string
* @return File object or false if it is not found
* @todo Implement searching for old file versions(?)
*/
function findFile( $title ) {
if( !( $title instanceof Title ) ) {
$title = Title::makeTitleSafe( NS_FILE, $title );
}
if( !$title ) {
return false; // invalid title?
}
$dbkey = $title->getDBkey();
if( array_key_exists( $dbkey, $this->cache ) ) {
wfDebug( "FileCache HIT for $dbkey\n" );
return $this->cache[$dbkey];
}
if( array_key_exists( $dbkey, $this->notFound ) ) {
wfDebug( "FileCache negative HIT for $dbkey\n" );
return false;
}
// Not in cache, fall back to a direct query
$file = $this->repoGroup->findFile( $title );
if( $file ) {
wfDebug( "FileCache MISS for $dbkey\n" );
$this->cache[$dbkey] = $file;
} else {
wfDebug( "FileCache negative MISS for $dbkey\n" );
$this->notFound[$dbkey] = true;
}
return $file;
}
/**
* Search the cache for multiple files.
* @param array $titles Title objects or strings to search for
* @return array of File objects, indexed by DB key
*/
function findFiles( $titles ) {
$titleObjs = array();
foreach ( $titles as $title ) {
if ( !( $title instanceof Title ) ) {
$title = Title::makeTitleSafe( NS_FILE, $title );
}
if ( $title ) {
$titleObjs[$title->getDBkey()] = $title;
}
}
$result = array_intersect_key( $this->cache, $titleObjs );
$unsure = array_diff_key( $titleObjs, $result, $this->notFound );
if( $unsure ) {
wfDebug( "FileCache MISS for ".count( $unsure )." files out of ".count( $titleObjs )."...\n" );
// XXX: We assume the array returned by findFiles() is
// indexed by DBkey; this appears to be true, but should
// be explicitly documented.
$found = $this->repoGroup->findFiles( $unsure );
$result += $found;
$this->addFiles( $found );
$this->markNotFound( array_keys( array_diff_key( $unsure, $found ) ) );
}
wfDebug( "FileCache found ".count( $result )." files out of ".count( $titleObjs )."\n" );
return $result;
}
}