MemcachedBackend.php

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<?php
namespace TYPO3\CMS\Core\Cache\Backend;

class MemcachedBackend extends \TYPO3\CMS\Core\Cache\Backend\AbstractBackend implements \TYPO3\CMS\Core\Cache\Backend\TaggableBackendInterface {

    const MAX_BUCKET_SIZE = 1048534;
    protected $memcache;

    protected $servers = array();

    protected $flags;

    protected $identifierPrefix;

    public function __construct($context, array $options = array()) {
        if (!extension_loaded('memcache')) {
            throw new \TYPO3\CMS\Core\Cache\Exception('The PHP extension "memcache" must be installed and loaded in ' . 'order to use the Memcached backend.', 1213987706);
        }
        parent::__construct($context, $options);
    }

    protected function setServers(array $servers) {
        $this->servers = $servers;
    }

    protected function setCompression($useCompression) {
        if ($useCompression === TRUE) {
            $this->flags ^= MEMCACHE_COMPRESSED;
        } else {
            $this->flags &= ~MEMCACHE_COMPRESSED;
        }
    }

    public function initializeObject() {
        if (!count($this->servers)) {
            throw new \TYPO3\CMS\Core\Cache\Exception('No servers were given to Memcache', 1213115903);
        }
        $this->memcache = new \Memcache();
        $defaultPort = ini_get('memcache.default_port');
        foreach ($this->servers as $server) {
            if (substr($server, 0, 7) == 'unix://') {
                $host = $server;
                $port = 0;
            } else {
                if (substr($server, 0, 6) === 'tcp://') {
                    $server = substr($server, 6);
                }
                if (strpos($server, ':') !== FALSE) {
                    list($host, $port) = explode(':', $server, 2);
                } else {
                    $host = $server;
                    $port = $defaultPort;
                }
            }
            $this->memcache->addserver($host, $port);
        }
    }

    public function setCache(\TYPO3\CMS\Core\Cache\Frontend\FrontendInterface $cache) {
        parent::setCache($cache);
        $identifierHash = substr(md5(PATH_site . $this->context . $this->cacheIdentifier), 0, 12);
        $this->identifierPrefix = 'TYPO3_' . $identifierHash . '_';
    }

    public function set($entryIdentifier, $data, array $tags = array(), $lifetime = NULL) {
        if (strlen($this->identifierPrefix . $entryIdentifier) > 250) {
            throw new \InvalidArgumentException('Could not set value. Key more than 250 characters (' . $this->identifierPrefix . $entryIdentifier . ').', 1232969508);
        }
        if (!$this->cache instanceof \TYPO3\CMS\Core\Cache\Frontend\FrontendInterface) {
            throw new \TYPO3\CMS\Core\Cache\Exception('No cache frontend has been set yet via setCache().', 1207149215);
        }
        if (!is_string($data)) {
            throw new \TYPO3\CMS\Core\Cache\Exception\InvalidDataException('The specified data is of type "' . gettype($data) . '" but a string is expected.', 1207149231);
        }
        $tags[] = '%MEMCACHEBE%' . $this->cacheIdentifier;
        $expiration = $lifetime !== NULL ? $lifetime : $this->defaultLifetime;
        // Memcached consideres values over 2592000 sec (30 days) as UNIX timestamp
        // thus $expiration should be converted from lifetime to UNIX timestamp
        if ($expiration > 2592000) {
            $expiration += $GLOBALS['EXEC_TIME'];
        }
        try {
            if (strlen($data) > self::MAX_BUCKET_SIZE) {
                $data = str_split($data, 1024 * 1000);
                $success = TRUE;
                $chunkNumber = 1;
                foreach ($data as $chunk) {
                    $success = $success && $this->memcache->set($this->identifierPrefix . $entryIdentifier . '_chunk_' . $chunkNumber, $chunk, $this->flags, $expiration);
                    $chunkNumber++;
                }
                $success = $success && $this->memcache->set($this->identifierPrefix . $entryIdentifier, 'TYPO3*chunked:' . $chunkNumber, $this->flags, $expiration);
            } else {
                $success = $this->memcache->set($this->identifierPrefix . $entryIdentifier, $data, $this->flags, $expiration);
            }
            if ($success === TRUE) {
                $this->removeIdentifierFromAllTags($entryIdentifier);
                $this->addIdentifierToTags($entryIdentifier, $tags);
            } else {
                throw new \TYPO3\CMS\Core\Cache\Exception('Could not set data to memcache server.', 1275830266);
            }
        } catch (\Exception $exception) {
            \TYPO3\CMS\Core\Utility\GeneralUtility::sysLog('Memcache: could not set value. Reason: ' . $exception->getMessage(), 'Core', \TYPO3\CMS\Core\Utility\GeneralUtility::SYSLOG_SEVERITY_WARNING);
        }
    }

    public function get($entryIdentifier) {
        $value = $this->memcache->get($this->identifierPrefix . $entryIdentifier);
        if (substr($value, 0, 14) === 'TYPO3*chunked:') {
            list(, $chunkCount) = explode(':', $value);
            $value = '';
            for ($chunkNumber = 1; $chunkNumber < $chunkCount; $chunkNumber++) {
                $value .= $this->memcache->get($this->identifierPrefix . $entryIdentifier . '_chunk_' . $chunkNumber);
            }
        }
        return $value;
    }

    public function has($entryIdentifier) {
        return $this->memcache->get($this->identifierPrefix . $entryIdentifier) !== FALSE;
    }

    public function remove($entryIdentifier) {
        $this->removeIdentifierFromAllTags($entryIdentifier);
        return $this->memcache->delete($this->identifierPrefix . $entryIdentifier, 0);
    }

    public function findIdentifiersByTag($tag) {
        $identifiers = $this->memcache->get($this->identifierPrefix . 'tag_' . $tag);
        if ($identifiers !== FALSE) {
            return (array) $identifiers;
        } else {
            return array();
        }
    }

    public function flush() {
        if (!$this->cache instanceof \TYPO3\CMS\Core\Cache\Frontend\FrontendInterface) {
            throw new \TYPO3\CMS\Core\Cache\Exception('No cache frontend has been set via setCache() yet.', 1204111376);
        }
        $this->flushByTag('%MEMCACHEBE%' . $this->cacheIdentifier);
    }

    public function flushByTag($tag) {
        $identifiers = $this->findIdentifiersByTag($tag);
        foreach ($identifiers as $identifier) {
            $this->remove($identifier);
        }
    }

    protected function addIdentifierToTags($entryIdentifier, array $tags) {
        // Get identifier-to-tag index to look for updates
        $existingTags = $this->findTagsByIdentifier($entryIdentifier);
        $existingTagsUpdated = FALSE;

        foreach ($tags as $tag) {
            // Update tag-to-identifier index
            $identifiers = $this->findIdentifiersByTag($tag);
            if (!in_array($entryIdentifier, $identifiers, TRUE)) {
                $identifiers[] = $entryIdentifier;
                $this->memcache->set($this->identifierPrefix . 'tag_' . $tag, $identifiers);
            }
            // Test if identifier-to-tag index needs update
            if (!in_array($tag, $existingTags, TRUE)) {
                $existingTags[] = $tag;
                $existingTagsUpdated = TRUE;
            }
        }

        // Update identifier-to-tag index if needed
        if ($existingTagsUpdated) {
            $this->memcache->set($this->identifierPrefix . 'ident_' . $entryIdentifier, $existingTags);
        }
    }

    protected function removeIdentifierFromAllTags($entryIdentifier) {
        // Get tags for this identifier
        $tags = $this->findTagsByIdentifier($entryIdentifier);
        // Deassociate tags with this identifier
        foreach ($tags as $tag) {
            $identifiers = $this->findIdentifiersByTag($tag);
            // Formally array_search() below should never return FALSE due to
            // the behavior of findTagsByIdentifier(). But if reverse index is
            // corrupted, we still can get 'FALSE' from array_search(). This is
            // not a problem because we are removing this identifier from
            // anywhere.
            if (($key = array_search($entryIdentifier, $identifiers)) !== FALSE) {
                unset($identifiers[$key]);
                if (count($identifiers)) {
                    $this->memcache->set($this->identifierPrefix . 'tag_' . $tag, $identifiers);
                } else {
                    $this->memcache->delete($this->identifierPrefix . 'tag_' . $tag, 0);
                }
            }
        }
        // Clear reverse tag index for this identifier
        $this->memcache->delete($this->identifierPrefix . 'ident_' . $entryIdentifier, 0);
    }

    protected function findTagsByIdentifier($identifier) {
        $tags = $this->memcache->get($this->identifierPrefix . 'ident_' . $identifier);
        return $tags === FALSE ? array() : (array) $tags;
    }

    public function collectGarbage() {

    }

}