Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle 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 3 of the License, or

// (at your option) any later version.

//

// Moodle 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.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**

 * The library file for the session cache store.

 *

 * This file is part of the session cache store, it contains the API for interacting with an instance of the store.

 * This is used as a default cache store within the Cache API. It should never be deleted.

 *

 * @package    cachestore_session

 * @category   cache

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

defined('MOODLE_INTERNAL') || die();

/**

 * The session data store class.

 *

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class session_data_store extends cache_store {

    /**

     * Used for the actual storage.

     * @var array

     */

    private static $sessionstore = null;

    /**

     * Returns a static store by reference... REFERENCE SUPER IMPORTANT.

     *

     * @param string $id

     * @return array

     */

    protected static function &register_store_id($id) {

        if (is_null(self::$sessionstore)) {

            global $SESSION;

            if (!isset($SESSION->cachestore_session)) {

                $SESSION->cachestore_session = array();

            }

            self::$sessionstore =& $SESSION->cachestore_session;

        }

        if (!array_key_exists($id, self::$sessionstore)) {

            self::$sessionstore[$id] = array();

        }

        return self::$sessionstore[$id];

    }

    /**

     * Flushes the data belong to the given store id.

     * @param string $id

     */

    protected static function flush_store_by_id($id) {

        unset(self::$sessionstore[$id]);

        self::$sessionstore[$id] = array();

    }

    /**

     * Flushes the store of all data.

     */

    protected static function flush_store() {

        $ids = array_keys(self::$sessionstore);

        unset(self::$sessionstore);

        self::$sessionstore = array();

        foreach ($ids as $id) {

            self::$sessionstore[$id] = array();

        }

    }

}

/**

 * The Session store class.

 *

 * @copyright  2012 Sam Hemelryk

 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class cachestore_session extends session_data_store implements cache_is_key_aware, cache_is_searchable {

    /**

     * The name of the store

     * @var store

     */

    protected $name;

    /**

     * The store id (should be unique)

     * @var string

     */

    protected $storeid;

    /**

     * The store we use for data.

     * @var array

     */

    protected $store;

    /**

     * The ttl if there is one. Hopefully not.

     * @var int

     */

    protected $ttl = 0;

    /**

     * The maximum size for the store, or false if there isn't one.

     * @var bool|int

     */

    protected $maxsize = false;

    /**

     * The number of items currently being stored.

     * @var int

     */

    protected $storecount = 0;

    /**

     * Constructs the store instance.

     *

     * Noting that this function is not an initialisation. It is used to prepare the store for use.

     * The store will be initialised when required and will be provided with a cache_definition at that time.

     *

     * @param string $name

     * @param array $configuration

     */

    public function __construct($name, array $configuration = array()) {

        $this->name = $name;

    }

    /**

     * Returns the supported features as a combined int.

     *

     * @param array $configuration

     * @return int

     */

    public static function get_supported_features(array $configuration = array()) {

        return self::SUPPORTS_DATA_GUARANTEE +

               self::SUPPORTS_NATIVE_TTL +

               self::IS_SEARCHABLE;

    }

    /**

     * Returns false as this store does not support multiple identifiers.

     * (This optional function is a performance optimisation; it must be

     * consistent with the value from get_supported_features.)

     *

     * @return bool False

     */

    public function supports_multiple_identifiers() {

        return false;

    }

    /**

     * Returns the supported modes as a combined int.

     *

     * @param array $configuration

     * @return int

     */

    public static function get_supported_modes(array $configuration = array()) {

        return self::MODE_SESSION;

    }

    /**

     * Returns true if the store requirements are met.

     *

     * @return bool

     */

    public static function are_requirements_met() {

        return true;

    }

    /**

     * Returns true if the given mode is supported by this store.

     *

     * @param int $mode One of cache_store::MODE_*

     * @return bool

     */

    public static function is_supported_mode($mode) {

        return ($mode === self::MODE_SESSION);

    }

    /**

     * Initialises the cache.

     *

     * Once this has been done the cache is all set to be used.

     *

     * @param cache_definition $definition

     */

    public function initialise(cache_definition $definition) {

        $this->storeid = $definition->generate_definition_hash();

        $this->store = &self::register_store_id($this->name.'-'.$definition->get_id());

        $this->ttl = $definition->get_ttl();

        $maxsize = $definition->get_maxsize();

        if ($maxsize !== null) {

            // Must be a positive int.

            $this->maxsize = abs((int)$maxsize);

            $this->storecount = count($this->store);

        }

        $this->check_ttl();

    }

    /**

     * Returns true once this instance has been initialised.

     *

     * @return bool

     */

    public function is_initialised() {

        return (is_array($this->store));

    }

    /**

     * Retrieves an item from the cache store given its key.

     *

     * @param string $key The key to retrieve

     * @return mixed The data that was associated with the key, or false if the key did not exist.

     */

    public function get($key) {

        if (isset($this->store[$key])) {

            if ($this->ttl == 0) {

                $value = $this->store[$key][0];

                if ($this->maxsize !== false) {

                    // Make sure the element is now in the end of array.

                    $this->set($key, $value);

                }

                return $value;

            } else if ($this->store[$key][1] >= (cache::now() - $this->ttl)) {

                return $this->store[$key][0];

            } else {

                // Element is present but has expired.

                $this->check_ttl();

            }

        }

        return false;

    }

    /**

     * Retrieves several items from the cache store in a single transaction.

     *

     * If not all of the items are available in the cache then the data value for those that are missing will be set to false.

     *

     * @param array $keys The array of keys to retrieve

     * @return array An array of items from the cache. There will be an item for each key, those that were not in the store will

     *      be set to false.

     */

    public function get_many($keys) {

        $return = array();

        $maxtime = 0;

        if ($this->ttl != 0) {

            $maxtime = cache::now() - $this->ttl;

        }

        $hasexpiredelements = false;

        foreach ($keys as $key) {

            $return[$key] = false;

            if (isset($this->store[$key])) {

                if ($this->ttl == 0) {

                    $return[$key] = $this->store[$key][0];

                    if ($this->maxsize !== false) {

                        // Make sure the element is now in the end of array.

                        $this->set($key, $return[$key], false);

                    }

                } else if ($this->store[$key][1] >= $maxtime) {

                    $return[$key] = $this->store[$key][0];

                } else {

                    $hasexpiredelements = true;

                }

            }

        }

        if ($hasexpiredelements) {

            // There are some elements that are present but have expired.

            $this->check_ttl();

        }

        return $return;

    }

    /**

     * Sets an item in the cache given its key and data value.

     *

     * @param string $key The key to use.

     * @param mixed $data The data to set.

     * @param bool $testmaxsize If set to true then we test the maxsize arg and reduce if required. If this is set to false you will

     *      need to perform these checks yourself. This allows for bulk set's to be performed and maxsize tests performed once.

     * @return bool True if the operation was a success false otherwise.

     */

    public function set($key, $data, $testmaxsize = true) {

        $testmaxsize = ($testmaxsize && $this->maxsize !== false);

        $increment = $this->maxsize !== false && !isset($this->store[$key]);

        if (($this->maxsize !== false && !$increment) || $this->ttl != 0) {

            // Make sure the element is added to the end of $this->store array.

            unset($this->store[$key]);

        }

        if ($this->ttl === 0) {

            $this->store[$key] = array($data, 0);

        } else {

            $this->store[$key] = array($data, cache::now());

        }

        if ($increment) {

            $this->storecount++;

        }

        if ($testmaxsize && $this->storecount > $this->maxsize) {

            $this->reduce_for_maxsize();

        }

        return true;

    }

    /**

     * Sets many items in the cache in a single transaction.

     *

     * @param array $keyvaluearray An array of key value pairs. Each item in the array will be an associative array with two

     *      keys, 'key' and 'value'.

     * @return int The number of items successfully set. It is up to the developer to check this matches the number of items

     *      sent ... if they care that is.

     */

    public function set_many(array $keyvaluearray) {

        $count = 0;

        $increment = 0;

        foreach ($keyvaluearray as $pair) {

            $key = $pair['key'];

            $data = $pair['value'];

            $count++;

            if ($this->maxsize !== false || $this->ttl !== 0) {

                // Make sure the element is added to the end of $this->store array.

                $this->delete($key);

                $increment++;

            } else if (!isset($this->store[$key])) {

                $increment++;

            }

            if ($this->ttl === 0) {

                $this->store[$key] = array($data, 0);

            } else {

                $this->store[$key] = array($data, cache::now());

            }

        }

        if ($this->maxsize !== false) {

            $this->storecount += $increment;

            if ($this->storecount > $this->maxsize) {

                $this->reduce_for_maxsize();

            }

        }

        return $count;

    }

    /**

     * Checks if the store has a record for the given key and returns true if so.

     *

     * @param string $key

     * @return bool

     */

    public function has($key) {

        if (isset($this->store[$key])) {

            if ($this->ttl == 0) {

                return true;

            } else if ($this->store[$key][1] >= (cache::now() - $this->ttl)) {

                return true;

            }

        }

        return false;

    }

    /**

     * Returns true if the store contains records for all of the given keys.

     *

     * @param array $keys

     * @return bool

     */

    public function has_all(array $keys) {

        $maxtime = 0;

        if ($this->ttl != 0) {

            $maxtime = cache::now() - $this->ttl;

        }

        foreach ($keys as $key) {

            if (!isset($this->store[$key])) {

                return false;

            }

            if ($this->ttl != 0 && $this->store[$key][1] < $maxtime) {

                return false;

            }

        }

        return true;

    }

    /**

     * Returns true if the store contains records for any of the given keys.

     *

     * @param array $keys

     * @return bool

     */

    public function has_any(array $keys) {

        $maxtime = 0;

        if ($this->ttl != 0) {

            $maxtime = cache::now() - $this->ttl;

        }

        foreach ($keys as $key) {

            if (isset($this->store[$key]) && ($this->ttl == 0 || $this->store[$key][1] >= $maxtime)) {

                return true;

            }

        }

        return false;

    }

    /**

     * Deletes an item from the cache store.

     *

     * @param string $key The key to delete.

     * @return bool Returns true if the operation was a success, false otherwise.

     */

    public function delete($key) {

        if (!isset($this->store[$key])) {

            return false;

        }

        unset($this->store[$key]);

        if ($this->maxsize !== false) {

            $this->storecount--;

        }

        return true;

    }

    /**

     * Deletes several keys from the cache in a single action.

     *

     * @param array $keys The keys to delete

     * @return int The number of items successfully deleted.

     */

    public function delete_many(array $keys) {

        // The number of items that have actually being removed.

        $reduction = 0;

        foreach ($keys as $key) {

            if (isset($this->store[$key])) {

                $reduction++;

            }

            unset($this->store[$key]);

        }

        if ($this->maxsize !== false) {

            $this->storecount -= $reduction;

        }

        return $reduction;

    }

    /**

     * Purges the cache deleting all items within it.

     *

     * @return boolean True on success. False otherwise.

     */

    public function purge() {

        $this->store = array();

        // Don't worry about checking if we're using max size just set it as thats as fast as the check.

        $this->storecount = 0;

        return true;

    }

    /**

     * Reduces the size of the array if maxsize has been hit.

     *

     * This function reduces the size of the store reducing it by 10% of its maxsize.

     * It removes the oldest items in the store when doing this.

     * The reason it does this an doesn't use a least recently used system is purely the overhead such a system

     * requires. The current approach is focused on speed, MUC already adds enough overhead to static/session caches

     * and avoiding more is of benefit.

     *

     * @return int

     */

    protected function reduce_for_maxsize() {

        $diff = $this->storecount - $this->maxsize;

        if ($diff < 1) {

            return 0;

        }

        // Reduce it by an extra 10% to avoid calling this repetitively if we are in a loop.

        $diff += floor($this->maxsize / 10);

        $this->store = array_slice($this->store, $diff, null, true);

        $this->storecount -= $diff;

        return $diff;

    }

    /**

     * Returns true if the user can add an instance of the store plugin.

     *

     * @return bool

     */

    public static function can_add_instance() {

        return false;

    }

    /**

     * Performs any necessary clean up when the store instance is being deleted.

     */

    public function instance_deleted() {

        $this->purge();

    }

    /**

     * Generates an instance of the cache store that can be used for testing.

     *

     * @param cache_definition $definition

     * @return cachestore_session

     */

    public static function initialise_test_instance(cache_definition $definition) {

        // Do something here perhaps.

        $cache = new cachestore_session('Session test');

        $cache->initialise($definition);

        return $cache;

    }

    /**

     * Generates the appropriate configuration required for unit testing.

     *

     * @return array Array of unit test configuration data to be used by initialise().

     */

    public static function unit_test_configuration() {

        return array();

    }

    /**

     * Returns the name of this instance.

     * @return string

     */

    public function my_name() {

        return $this->name;

    }

    /**

     * Removes expired elements.

     * @return int number of removed elements

     */

    protected function check_ttl() {

        if ($this->ttl === 0) {

            return 0;

        }

        $maxtime = cache::now() - $this->ttl;

        $count = 0;

        for ($value = reset($this->store); $value !== false; $value = next($this->store)) {

            if ($value[1] >= $maxtime) {

                // We know that elements are sorted by ttl so no need to continue.

                break;

            }

            $count++;

        }

        if ($count) {

            // Remove first $count elements as they are expired.

            $this->store = array_slice($this->store, $count, null, true);

            if ($this->maxsize !== false) {

                $this->storecount -= $count;

            }

        }

        return $count;

    }

    /**

     * Finds all of the keys being stored in the cache store instance.

     *

     * @return array

     */

    public function find_all() {

        $this->check_ttl();

        return array_keys($this->store);

    }

    /**

     * Finds all of the keys whose keys start with the given prefix.

     *

     * @param string $prefix

     * @return array An array of keys.

     */

    public function find_by_prefix($prefix) {

        $return = array();

        foreach ($this->find_all() as $key) {

            if (strpos($key, $prefix) === 0) {

                $return[] = $key;

            }

        }

        return $return;

    }

    /**

     * This store supports native TTL handling.

     * @return bool

     */

    public function store_supports_native_ttl() {

        return true;

    }

}