class.t3lib_cache_backend_apcbackend.php

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<?php
/***************************************************************
 *  Copyright notice
 *
 *  (c) 2009-2011 Ingo Renner <ingo@typo3.org>
 *  All rights reserved
 *
 *  This script is part of the TYPO3 project. The TYPO3 project is
 *  free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  The GNU General Public License can be found at
 *  http://www.gnu.org/copyleft/gpl.html.
 *
 *  This script is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  This copyright notice MUST APPEAR in all copies of the script!
 ***************************************************************/


/**
 * A caching backend which stores cache entries by using APC.
 *
 * This backend uses the following types of keys:
 * - tag_xxx
 *   xxx is tag name, value is array of associated identifiers identifier. This
 *   is "forward" tag index. It is mainly used for obtaining content by tag
 *   (get identifier by tag -> get content by identifier)
 * - ident_xxx
 *   xxx is identifier, value is array of associated tags. This is "reverse" tag
 *   index. It provides quick access for all tags associated with this identifier
 *   and used when removing the identifier
 *
 * Each key is prepended with a prefix. By default prefix consists from two parts
 * separated by underscore character and ends in yet another underscore character:
 * - "TYPO3"
 * - MD5 of path to TYPO3 and user running TYPO3
 * This prefix makes sure that keys from the different installations do not
 * conflict.
 *
 * This file is a backport from FLOW3
 *
 * @package TYPO3
 * @subpackage t3lib_cache
 * @api
 * @version $Id: class.t3lib_cache_backend_apcbackend.php 10121 2011-01-18 20:15:30Z ohader $
 */
class t3lib_cache_backend_ApcBackend extends t3lib_cache_backend_AbstractBackend {

    /**
     * A prefix to seperate stored data from other data possible stored in the APC
     *
     * @var string
     */
    protected $identifierPrefix;

    /**
     * Constructs this backend
     *
     * @param array $options Configuration options - unused here
     * @author Robert Lemke <robert@typo3.org>
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function __construct(array $options = array()) {
        if (!extension_loaded('apc')) {
            throw new t3lib_cache_Exception(
                'The PHP extension "apc" must be installed and loaded in order to use the APC backend.',
                1232985414
            );
        }

        parent::__construct($options);
    }

    /**
     * Initializes the identifier prefix when setting the cache.
     *
     * @param t3lib_cache_frontend_Frontend $cache The frontend for this backend
     * @return void
     * @author Robert Lemke <robert@typo3.org>
     */
    public function setCache(t3lib_cache_frontend_Frontend $cache) {
        parent::setCache($cache);
        $processUser = extension_loaded('posix') ? posix_getpwuid(posix_geteuid()) : array('name' => 'default');
        $pathHash = t3lib_div::shortMD5(PATH_site . $processUser['name'], 12);
        $this->identifierPrefix = 'TYPO3_' . $pathHash;
    }

    /**
     * Saves data in the cache.
     *
     * @param string $entryIdentifier An identifier for this specific cache entry
     * @param string $data The data to be stored
     * @param array $tags Tags to associate with this cache entry
     * @param integer $lifetime Lifetime of this cache entry in seconds. If NULL is specified, the default lifetime is used. "0" means unlimited liftime.
     * @return void
     * @throws t3lib_cache_Exception if no cache frontend has been set.
     * @throws InvalidArgumentException if the identifier is not valid
     * @throws t3lib_cache_exception_InvalidData if $data is not a string
     * @author Christian Jul Jensen <julle@typo3.org>
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function set($entryIdentifier, $data, array $tags = array(), $lifetime = NULL) {
        if (!$this->cache instanceof t3lib_cache_frontend_Frontend) {
            throw new t3lib_cache_Exception(
                'No cache frontend has been set yet via setCache().',
                1232986818
            );
        }

        if (!is_string($data)) {
            throw new t3lib_cache_exception_InvalidData(
                'The specified data is of type "' . gettype($data) . '" but a string is expected.',
                1232986825
            );
        }

        $tags[] = '%APCBE%' . $this->cacheIdentifier;
        $expiration = $lifetime !== NULL ? $lifetime : $this->defaultLifetime;

        $success = apc_store($this->identifierPrefix . $entryIdentifier, $data, $expiration);
        if ($success === TRUE) {
            $this->removeIdentifierFromAllTags($entryIdentifier);
            $this->addIdentifierToTags($entryIdentifier, $tags);
        } else {
            throw new t3lib_cache_Exception(
                'Could not set value.',
                1232986877
            );
        }
    }

    /**
     * Loads data from the cache.
     *
     * @param string $entryIdentifier An identifier which describes the cache entry to load
     * @return mixed The cache entry's content as a string or FALSE if the cache entry could not be loaded
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function get($entryIdentifier) {
        $success = FALSE;
        $value = apc_fetch($this->identifierPrefix . $entryIdentifier, $success);

        return ($success ? $value : $success);
    }

    /**
     * Checks if a cache entry with the specified identifier exists.
     *
     * @param string $entryIdentifier An identifier specifying the cache entry
     * @return boolean TRUE if such an entry exists, FALSE if not
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function has($entryIdentifier) {
        $success = FALSE;
        apc_fetch($this->identifierPrefix . $entryIdentifier, $success);
        return $success;
    }

    /**
     * Removes all cache entries matching the specified identifier.
     * Usually this only affects one entry but if - for what reason ever -
     * old entries for the identifier still exist, they are removed as well.
     *
     * @param string $entryIdentifier Specifies the cache entry to remove
     * @return boolean TRUE if (at least) an entry could be removed or FALSE if no entry was found
     * @author Christian Jul Jensen <julle@typo3.org>
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function remove($entryIdentifier) {
        $this->removeIdentifierFromAllTags($entryIdentifier);

        return apc_delete($this->identifierPrefix . $entryIdentifier);
    }

    /**
     * Finds and returns all cache entry identifiers which are tagged by the
     * specified tag.
     *
     * @param string $tag The tag to search for
     * @return array An array with identifiers of all matching entries. An empty array if no entries matched
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function findIdentifiersByTag($tag) {
        $success = FALSE;
        $identifiers = apc_fetch($this->identifierPrefix . 'tag_' . $tag, $success);

        if ($success === FALSE) {
            return array();
        } else {
            return (array) $identifiers;
        }
    }

    /**
     * Finds and returns all cache entry identifiers which are tagged by the
     * specified tags.
     *
     * @param array Array of tags to search for
     * @return array An array with identifiers of all matching entries. An empty array if no entries matched
     * @author Ingo Renner <ingo@typo3.org>
     */
    public function findIdentifiersByTags(array $tags) {
        $taggedEntries = array();
        $foundEntries = array();

        foreach ($tags as $tag) {
            $taggedEntries[$tag] = $this->findIdentifiersByTag($tag);
        }

        $intersectedTaggedEntries = call_user_func_array('array_intersect', $taggedEntries);

        foreach ($intersectedTaggedEntries as $entryIdentifier) {
            if ($this->has($entryIdentifier)) {
                $foundEntries[$entryIdentifier] = $entryIdentifier;
            }
        }

        return $foundEntries;
    }

    /**
     * Finds all tags for the given identifier. This function uses reverse tag
     * index to search for tags.
     *
     * @param string $identifier Identifier to find tags by
     * @return array Array with tags
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    protected function findTagsByIdentifier($identifier) {
        $success = FALSE;
        $tags = apc_fetch($this->identifierPrefix . 'ident_' . $identifier, $success);

        return ($success ? (array) $tags : array());
    }

    /**
     * Removes all cache entries of this cache.
     *
     * @return void
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function flush() {
        if (!$this->cache instanceof t3lib_cache_frontend_Frontend) {
            throw new t3lib_cache_Exception(
                'Yet no cache frontend has been set via setCache().',
                1232986971
            );
        }

        $this->flushByTag('%APCBE%' . $this->cacheIdentifier);
    }

    /**
     * Removes all cache entries of this cache which are tagged by the specified
     * tag.
     *
     * @param string $tag The tag the entries must have
     * @return void
     * @author Karsten Dambekalns <karsten@typo3.org>
     */
    public function flushByTag($tag) {
        $identifiers = $this->findIdentifiersByTag($tag);

        foreach ($identifiers as $identifier) {
            $this->remove($identifier);
        }
    }

    /**
     * Removes all cache entries of this cache which are tagged by the specified tag.
     *
     * @param array The tags the entries must have
     * @return void
     * @author Ingo Renner <ingo@typo3.org>
     */
    public function flushByTags(array $tags) {
        foreach ($tags as $tag) {
            $this->flushByTag($tag);
        }
    }

    /**
     * Associates the identifier with the given tags
     *
     * @param string $entryIdentifier
     * @param array $tags
     * @author Karsten Dambekalns <karsten@typo3.org>
     * @author Dmitry Dulepov <dmitry.@typo3.org>
     */
    protected function addIdentifierToTags($entryIdentifier, array $tags) {
        foreach ($tags as $tag) {
                // Update tag-to-identifier index
            $identifiers = $this->findIdentifiersByTag($tag);
            if (array_search($entryIdentifier, $identifiers) === FALSE) {
                $identifiers[] = $entryIdentifier;
                apc_store($this->identifierPrefix . 'tag_' . $tag, $identifiers);
            }

                // Update identifier-to-tag index
            $existingTags = $this->findTagsByIdentifier($entryIdentifier);
            if (array_search($entryIdentifier, $existingTags) === false) {
                apc_store($this->identifierPrefix . 'ident_' . $entryIdentifier, array_merge($existingTags, $tags));
            }

        }
    }

    /**
     * Removes association of the identifier with the given tags
     *
     * @param string $entryIdentifier
     * @param array $tags
     * @author Karsten Dambekalns <karsten@typo3.org>
     * @author Dmitry Dulepov <dmitry.@typo3.org>
     */
    protected function removeIdentifierFromAllTags($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)) {
                    apc_store($this->identifierPrefix . 'tag_' . $tag, $identifiers);
                } else {
                    apc_delete($this->identifierPrefix . 'tag_' . $tag);
                }
            }
        }
            // Clear reverse tag index for this identifier
        apc_delete($this->identifierPrefix . 'ident_' . $entryIdentifier);
    }

    /**
     * Does nothing, as APC does GC itself
     *
     * @return void
     */
    public function collectGarbage() {

    }
}


if (defined('TYPO3_MODE') && isset($GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['XCLASS']['t3lib/cache/backend/class.t3lib_cache_backend_apcbackend.php'])) {
    include_once($GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['XCLASS']['t3lib/cache/backend/class.t3lib_cache_backend_apcbackend.php']);
}

?>