FileCacheBase.php

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<?php
abstract class FileCacheBase {
        protected $mKey;
        protected $mType = 'object';
        protected $mExt = 'cache';
        protected $mFilePath;
        protected $mUseGzip;
        /* lazy loaded */
        protected $mCached;

        /* @TODO: configurable? */
        const MISS_FACTOR = 15; // log 1 every MISS_FACTOR cache misses
        const MISS_TTL_SEC = 3600; // how many seconds ago is "recent"

        protected function __construct() {
                global $wgUseGzip;

                $this->mUseGzip = (bool)$wgUseGzip;
        }

        final protected function baseCacheDirectory() {
                global $wgFileCacheDirectory;
                return $wgFileCacheDirectory;
        }

        abstract protected function cacheDirectory();

        protected function cachePath() {
                if ( $this->mFilePath !== null ) {
                        return $this->mFilePath;
                }

                $dir = $this->cacheDirectory();
                # Build directories (methods include the trailing "/")
                $subDirs = $this->typeSubdirectory() . $this->hashSubdirectory();
                # Avoid extension confusion
                $key = str_replace( '.', '%2E', urlencode( $this->mKey ) );
                # Build the full file path
                $this->mFilePath = "{$dir}/{$subDirs}{$key}.{$this->mExt}";
                if ( $this->useGzip() ) {
                        $this->mFilePath .= '.gz';
                }

                return $this->mFilePath;
        }

        public function isCached() {
                if ( $this->mCached === null ) {
                        $this->mCached = file_exists( $this->cachePath() );
                }
                return $this->mCached;
        }

        public function cacheTimestamp() {
                $timestamp = filemtime( $this->cachePath() );
                return ( $timestamp !== false )
                        ? wfTimestamp( TS_MW, $timestamp )
                        : false;
        }

        public function isCacheGood( $timestamp = '' ) {
                global $wgCacheEpoch;

                if ( !$this->isCached() ) {
                        return false;
                }

                $cachetime = $this->cacheTimestamp();
                $good = ( $timestamp <= $cachetime && $wgCacheEpoch <= $cachetime );
                wfDebug( __METHOD__ . ": cachetime $cachetime, touched '{$timestamp}' epoch {$wgCacheEpoch}, good $good\n" );

                return $good;
        }

        protected function useGzip() {
                return $this->mUseGzip;
        }

        public function fetchText() {
                if( $this->useGzip() ) {
                        $fh = gzopen( $this->cachePath(), 'rb' );
                        return stream_get_contents( $fh );
                } else {
                        return file_get_contents( $this->cachePath() );
                }
        }

        public function saveText( $text ) {
                global $wgUseFileCache;

                if ( !$wgUseFileCache ) {
                        return false;
                }

                if ( $this->useGzip() ) {
                        $text = gzencode( $text );
                }

                $this->checkCacheDirs(); // build parent dir
                if ( !file_put_contents( $this->cachePath(), $text, LOCK_EX ) ) {
                        wfDebug( __METHOD__ . "() failed saving ". $this->cachePath() . "\n");
                        $this->mCached = null;
                        return false;
                }

                $this->mCached = true;
                return $text;
        }

        public function clearCache() {
                wfSuppressWarnings();
                unlink( $this->cachePath() );
                wfRestoreWarnings();
                $this->mCached = false;
        }

        protected function checkCacheDirs() {
                wfMkdirParents( dirname( $this->cachePath() ), null, __METHOD__ );
        }

        protected function typeSubdirectory() {
                return $this->mType . '/';
        }

        protected function hashSubdirectory() {
                global $wgFileCacheDepth;

                $subdir = '';
                if ( $wgFileCacheDepth > 0 ) {
                        $hash = md5( $this->mKey );
                        for ( $i = 1; $i <= $wgFileCacheDepth; $i++ ) {
                                $subdir .= substr( $hash, 0, $i ) . '/';
                        }
                }

                return $subdir;
        }

        public function incrMissesRecent( WebRequest $request ) {
                global $wgMemc;
                if ( mt_rand( 0, self::MISS_FACTOR - 1 ) == 0 ) {
                        # Get a large IP range that should include the user  even if that 
                        # person's IP address changes
                        $ip = $request->getIP();
                        if ( !IP::isValid( $ip ) ) {
                                return;
                        }
                        $ip = IP::isIPv6( $ip )
                                ? IP::sanitizeRange( "$ip/32" )
                                : IP::sanitizeRange( "$ip/16" );

                        # Bail out if a request already came from this range...
                        $key = wfMemcKey( get_class( $this ), 'attempt', $this->mType, $this->mKey, $ip );
                        if ( $wgMemc->get( $key ) ) {
                                return; // possibly the same user
                        }
                        $wgMemc->set( $key, 1, self::MISS_TTL_SEC );

                        # Increment the number of cache misses...
                        $key = $this->cacheMissKey();
                        if ( $wgMemc->get( $key ) === false ) {
                                $wgMemc->set( $key, 1, self::MISS_TTL_SEC );
                        } else {
                                $wgMemc->incr( $key );
                        }
                }
        }

        public function getMissesRecent() {
                global $wgMemc;
                return self::MISS_FACTOR * $wgMemc->get( $this->cacheMissKey() );
        }

        protected function cacheMissKey() {
                return wfMemcKey( get_class( $this ), 'misses', $this->mType, $this->mKey );
        }
}