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<?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 $id
* @return array
*/
protected static function ®ister_store_id($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;
}
}