includes/filerepo/FileCache.php

   1 <?php
   2 /**
   3  * Cache of file objects, wrapping some RepoGroup functions to avoid redundant
   4  * queries.  Loosely inspired by the LinkCache / LinkBatch classes for titles.
   5  *
   6  * ISSUE: Merge with RepoGroup?
   7  *
   8  * @ingroup FileRepo
   9  */
  10 class FileCache {
  11         var $repoGroup;
  12         var $cache = array(), $oldCache = array(), $notFound = array();
  13
  14         protected static $instance;
  15
  16         /**
  17          * Get a FileCache instance.  Typically, only one instance of FileCache
  18          * is needed in a MediaWiki invocation.
  19          */
  20         static function singleton() {
  21                 if ( self::$instance ) {
  22                         return self::$instance;
  23                 }
  24                 self::$instance = new FileCache( RepoGroup::singleton() );
  25                 return self::$instance;
  26         }
  27
  28         /**
  29          * Destroy the singleton instance, so that a new one will be created next
  30          * time singleton() is called.
  31          */
  32         static function destroySingleton() {
  33                 self::$instance = null;
  34         }
  35
  36         /**
  37          * Set the singleton instance to a given object
  38          */
  39         static function setSingleton( $instance ) {
  40                 self::$instance = $instance;
  41         }
  42
  43         /**
  44          * Construct a group of file repositories.
  45          * @param RepoGroup $repoGroup
  46          */
  47         function __construct( $repoGroup ) {
  48                 $this->repoGroup = $repoGroup;
  49         }
  50
  51
  52         /**
  53          * Add some files to the cache.  This is a fairly low-level function,
  54          * which most users should not need to call.  Note that any existing
  55          * entries for the same keys will not be replaced.  Call clearFiles()
  56          * first if you need that.
  57          * @param array $files array of File objects, indexed by DB key
  58          */
  59         function addFiles( $files ) {
  60                 wfDebug( "FileCache adding ".count( $files )." files\n" );
  61                 $this->cache += $files;
  62         }
  63
  64         /**
  65          * Remove some files from the cache, so that their existence will be
  66          * rechecked.  This is a fairly low-level function, which most users
  67          * should not need to call.
  68          * @param array $remove array indexed by DB keys to remove (the values are ignored)
  69          */
  70         function clearFiles( $remove ) {
  71                 wfDebug( "FileCache clearing data for ".count( $remove )." files\n" );
  72                 $this->cache = array_diff_key( $this->cache, $remove );
  73                 $this->notFound = array_diff_key( $this->notFound, $remove );
  74         }
  75
  76         /**
  77          * Mark some DB keys as nonexistent.  This is a fairly low-level
  78          * function, which most users should not need to call.
  79          * @param array $dbkeys array of DB keys
  80          */
  81         function markNotFound( $dbkeys ) {
  82                 wfDebug( "FileCache marking ".count( $dbkeys )." files as not found\n" );
  83                 $this->notFound += array_fill_key( $dbkeys, true );
  84         }
  85
  86
  87         /**
  88          * Search the cache for a file.
  89          * @param mixed $title Title object or string
  90          * @param string or false $time, old version time
  91          * @return File object or false if it is not found
  92          */
  93         function findFile( $title, $time = false ) {
  94                 if( !( $title instanceof Title ) ) {
  95                         $title = Title::makeTitleSafe( NS_FILE, $title );
  96                 }
  97                 if( !$title ) {
  98                         return false;  // invalid title?
  99                 }
 100
 101                 $dbkey = $title->getDBkey();
 102                 # Is there a current version cached?
 103                 if( array_key_exists( $dbkey, $this->cache ) ) {
 104                         if( !$time || $this->cache[$dbkey]->getTimestamp() === $time ) {
 105                                 wfDebug( "FileCache HIT for $dbkey\n" );
 106                                 return $this->cache[$dbkey];
 107                         }
 108                 }
 109                 # Is there no current version? Then assume no old versions too.
 110                 if( array_key_exists( $dbkey, $this->notFound ) ) {
 111                         wfDebug( "FileCache negative HIT for $dbkey\n" );
 112                         return false;
 113                 }
 114                 # Is this old version cached?
 115                 if( $time && array_key_exists( $dbkey, $this->oldCache ) &&
 116                         array_key_exists( $time, $this->oldCache[$dbkey] ) )
 117                 {
 118                         wfDebug( "FileCache HIT for $dbkey on $time\n" );
 119                         return $this->oldCache[$dbkey][$time];
 120                 }
 121
 122                 // Not in cache, fall back to a direct query
 123                 $file = $this->repoGroup->findFile( $title, $time );
 124                 if( $file ) {
 125                         wfDebug( "FileCache MISS for $dbkey\n" );
 126                         if( !$file->isOld() ) {
 127                                 $this->cache[$dbkey] = $file; // cache the current version
 128                         }
 129                         if( !array_key_exists( $dbkey, $this->oldCache ) ) {
 130                                 $this->oldCache[$dbkey] = array();
 131                         }
 132                         $this->oldCache[$dbkey][$file->getTimestamp()] = $file; // cache this version
 133                 } else {
 134                         wfDebug( "FileCache negative MISS for $dbkey\n" );
 135                         $this->notFound[$dbkey] = true;
 136                 }
 137                 return $file;
 138         }
 139
 140         /**
 141          * Search the cache for multiple files.
 142          * @param array $titles Title objects or strings to search for
 143          * @return array of File objects, indexed by DB key
 144          */
 145         function findFiles( $titles ) {
 146                 $titleObjs = array();
 147                 foreach ( $titles as $title ) {
 148                         if ( !( $title instanceof Title ) ) {
 149                                 $title = Title::makeTitleSafe( NS_FILE, $title );
 150                         }
 151                         if ( $title ) {
 152                                 $titleObjs[$title->getDBkey()] = $title;
 153                         }
 154                 }
 155
 156                 $result = array_intersect_key( $this->cache, $titleObjs );
 157
 158                 $unsure = array_diff_key( $titleObjs, $result, $this->notFound );
 159                 if( $unsure ) {
 160                         wfDebug( "FileCache MISS for ".count( $unsure )." files out of ".count( $titleObjs )."...\n" );
 161                         // XXX: We assume the array returned by findFiles() is
 162                         // indexed by DBkey; this appears to be true, but should
 163                         // be explicitly documented.
 164                         $found = $this->repoGroup->findFiles( $unsure );
 165                         $result += $found;
 166                         $this->addFiles( $found );
 167                         $this->markNotFound( array_keys( array_diff_key( $unsure, $found ) ) );
 168                 }
 169
 170                 wfDebug( "FileCache found ".count( $result )." files out of ".count( $titleObjs )."\n" );
 171                 return $result;
 172         }
 173 }