* @link http://www.yiiframework.com/
* @copyright Copyright © 2008-2011 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
/**
* CCache is the base class for cache classes with different cache storage implementation.
*
* A data item can be stored in cache by calling {@link set} and be retrieved back
* later by {@link get}. In both operations, a key identifying the data item is required.
* An expiration time and/or a dependency can also be specified when calling {@link set}.
* If the data item expires or the dependency changes, calling {@link get} will not
* return back the data item.
*
* Note, by definition, cache does not ensure the existence of a value
* even if it does not expire. Cache is not meant to be a persistent storage.
*
* CCache implements the interface {@link ICache} with the following methods:
*
* - {@link get} : retrieve the value with a key (if any) from cache
* - {@link set} : store the value with a key into cache
* - {@link add} : store the value only if cache does not have this key
* - {@link delete} : delete the value with the specified key from cache
* - {@link flush} : delete all values from cache
*
*
* Child classes must implement the following methods:
*
* - {@link getValue}
* - {@link setValue}
* - {@link addValue}
* - {@link deleteValue}
* - {@link flushValues} (optional)
* - {@link serializeValue} (optional)
* - {@link unserializeValue} (optional)
*
*
* CCache also implements ArrayAccess so that it can be used like an array.
*
* @author Qiang Xue
* @version $Id$
* @package system.caching
* @since 1.0
*/
abstract class Cache extends ApplicationComponent implements \ArrayAccess
{
/**
* @var string a string prefixed to every cache key so that it is unique. Defaults to null which means
* to use the {@link CApplication::getId() application ID}. If different applications need to access the same
* pool of cached data, the same prefix should be set for each of the applications explicitly.
*/
public $keyPrefix;
/**
* @var boolean whether to md5-hash the cache key for normalization purposes. Defaults to true. Setting this property to false makes sure the cache
* key will not be tampered when calling the relevant methods {@link get()}, {@link set()}, {@link add()} and {@link delete()}. This is useful if a Yii
* application as well as an external application need to access the same cache pool (also see description of {@link keyPrefix} regarding this use case).
* However, without normalization you should make sure the affected cache backend does support the structure (charset, length, etc.) of all the provided
* cache keys, otherwise there might be unexpected behavior.
* @since 1.1.11
**/
public $hashKey = true;
/**
* @var boolean whether to automatically serialize/unserialize the cache values. Defaults to true. Setting this property to false makes sure the cache
* value will not be tampered when calling the methods {@link set()} and {@link add()}. This is useful in case you want to store data which simply
* does not require serialization (e.g. integers, strings or raw binary data). Thus there might be a small increase in performance and a smaller overall
* cache size. Take in mind that you will be unable to store PHP structures like arrays or objects, you would have to serialize and unserialize them manually.
* Another negative side effect is that providing a dependency via {@link set()} or {@link add()} will have no effect since dependencies rely on serialization.
* Since all the relevant core application components rely on dependency support, you should be very careful disabling this feature. Usually you want to
* configure a dedicated cache component for the sole purpose of storing raw unserialized data, the main cache component should always support serialization.
* @since 1.1.11
**/
public $autoSerialize = true;
/**
* @var boolean wether to make use of the {@link http://pecl.php.net/package/igbinary igbinary} serializer for cache entry serialization. Defaults to false.
* NOTE: If this is set to true while the igbinary extension has not been loaded, cache serialization will silently fall back to PHP's default
* serializer. Since the two serialization formats are incompatible, caches should be purged before switching this on to prevent errors.
* @since 1.1.11
*/
public $useIgbinarySerializer = false;
/**
* Initializes the application component.
* This method overrides the parent implementation by setting default cache key prefix.
*/
public function init()
{
parent::init();
if ($this->keyPrefix === null) {
$this->keyPrefix = Yii::app()->getId();
}
$this->useIgbinarySerializer = $this->useIgbinarySerializer && extension_loaded('igbinary');
}
/**
* @param string $key a key identifying a value to be cached
* @return sring a key generated from the provided key which ensures the uniqueness across applications
*/
protected function generateUniqueKey($key)
{
return $this->hashKey ? md5($this->keyPrefix . $key) : $this->keyPrefix . $key;
}
/**
* Retrieves a value from cache with a specified key.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache, expired or the dependency has changed.
*/
public function get($id)
{
if (($value = $this->getValue($this->generateUniqueKey($id))) !== false) {
$data = $this->autoSerialize ? $this->unserializeValue($value) : $value;
if (!$this->autoSerialize || (is_array($data) && (!($data[1] instanceof ICacheDependency) || !$data[1]->getHasChanged()))) {
Yii::trace('Serving "' . $id . '" from cache', 'system.caching.' . get_class($this));
return $this->autoSerialize ? $data[0] : $data;
}
}
return false;
}
/**
* Retrieves multiple values from cache with the specified keys.
* Some caches (such as memcache, apc) allow retrieving multiple cached values at one time,
* which may improve the performance since it reduces the communication cost.
* In case a cache doesn't support this feature natively, it will be simulated by this method.
* @param array $ids list of keys identifying the cached values
* @return array list of cached values corresponding to the specified keys. The array
* is returned in terms of (key,value) pairs.
* If a value is not cached or expired, the corresponding array value will be false.
*/
public function mget($ids)
{
$uniqueIDs = array();
$results = array();
foreach ($ids as $id) {
$uniqueIDs[$id] = $this->generateUniqueKey($id);
$results[$id] = false;
}
$values = $this->getValues($uniqueIDs);
foreach ($uniqueIDs as $id => $uniqueID) {
if (!isset($values[$uniqueID])) {
continue;
}
$data = $this->autoSerialize ? $this->unserializeValue($values[$uniqueID]) : $values[$uniqueID];
if (!$this->autoSerialize || (is_array($data) && (!($data[1] instanceof ICacheDependency) || !$data[1]->getHasChanged()))) {
Yii::trace('Serving "' . $id . '" from cache', 'system.caching.' . get_class($this));
$results[$id] = $this->autoSerialize ? $data[0] : $data;
}
}
return $results;
}
/**
* Stores a value identified by a key into cache.
* If the cache already contains such a key, the existing value and
* expiration time will be replaced with the new ones.
*
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function set($id, $value, $expire = 0, $dependency = null)
{
Yii::trace('Saving "' . $id . '" to cache', 'system.caching.' . get_class($this));
if ($dependency !== null && $this->autoSerialize) {
$dependency->evaluateDependency();
}
$data = $this->autoSerialize ? $this->serializeValue(array($value, $dependency)) : $value;
return $this->setValue($this->generateUniqueKey($id), $data, $expire);
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* Nothing will be done if the cache already contains the key.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @param ICacheDependency $dependency dependency of the cached item. If the dependency changes, the item is labeled invalid.
* @return boolean true if the value is successfully stored into cache, false otherwise
*/
public function add($id, $value, $expire = 0, $dependency = null)
{
Yii::trace('Adding "' . $id . '" to cache', 'system.caching.' . get_class($this));
if ($dependency !== null && $this->autoSerialize) {
$dependency->evaluateDependency();
}
$data = $this->autoSerialize ? $this->serializeValue(array($value, $dependency)) : $value;
return $this->addValue($this->generateUniqueKey($id), $data, $expire);
}
/**
* Deletes a value with the specified key from cache
* @param string $id the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function delete($id)
{
Yii::trace('Deleting "' . $id . '" from cache', 'system.caching.' . get_class($this));
return $this->deleteValue($this->generateUniqueKey($id));
}
/**
* Deletes all values from cache.
* Be careful of performing this operation if the cache is shared by multiple applications.
* @return boolean whether the flush operation was successful.
*/
public function flush()
{
Yii::trace('Flushing cache', 'system.caching.' . get_class($this));
return $this->flushValues();
}
/**
* Retrieves a value from cache with a specified key.
* This method should be implemented by child classes to retrieve the data
* from specific cache storage. The uniqueness and dependency are handled
* in {@link get()} already. So only the implementation of data retrieval
* is needed.
* @param string $key a unique key identifying the cached value
* @return string the value stored in cache, false if the value is not in the cache or expired.
* @throws CException if this method is not overridden by child classes
*/
protected function getValue($key)
{
throw new CException(Yii::t('yii', '{className} does not support get() functionality.',
array('{className}' => get_class($this))));
}
/**
* Retrieves multiple values from cache with the specified keys.
* The default implementation simply calls {@link getValue} multiple
* times to retrieve the cached values one by one.
* If the underlying cache storage supports multiget, this method should
* be overridden to exploit that feature.
* @param array $keys a list of keys identifying the cached values
* @return array a list of cached values indexed by the keys
*/
protected function getValues($keys)
{
$results = array();
foreach ($keys as $key) {
$results[$key] = $this->getValue($key);
}
return $results;
}
/**
* Stores a value identified by a key in cache.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link set()} already. So only the implementation of data storage
* is needed.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
* @throws CException if this method is not overridden by child classes
*/
protected function setValue($key, $value, $expire)
{
throw new CException(Yii::t('yii', '{className} does not support set() functionality.',
array('{className}' => get_class($this))));
}
/**
* Stores a value identified by a key into cache if the cache does not contain this key.
* This method should be implemented by child classes to store the data
* in specific cache storage. The uniqueness and dependency are handled
* in {@link add()} already. So only the implementation of data storage
* is needed.
*
* @param string $key the key identifying the value to be cached
* @param string $value the value to be cached
* @param integer $expire the number of seconds in which the cached value will expire. 0 means never expire.
* @return boolean true if the value is successfully stored into cache, false otherwise
* @throws CException if this method is not overridden by child classes
*/
protected function addValue($key, $value, $expire)
{
throw new CException(Yii::t('yii', '{className} does not support add() functionality.',
array('{className}' => get_class($this))));
}
/**
* Deletes a value with the specified key from cache
* This method should be implemented by child classes to delete the data from actual cache storage.
* @param string $key the key of the value to be deleted
* @return boolean if no error happens during deletion
* @throws CException if this method is not overridden by child classes
*/
protected function deleteValue($key)
{
throw new CException(Yii::t('yii', '{className} does not support delete() functionality.',
array('{className}' => get_class($this))));
}
/**
* Deletes all values from cache.
* Child classes may implement this method to realize the flush operation.
* @return boolean whether the flush operation was successful.
* @throws CException if this method is not overridden by child classes
* @since 1.1.5
*/
protected function flushValues()
{
throw new CException(Yii::t('yii', '{className} does not support flushValues() functionality.',
array('{className}' => get_class($this))));
}
/**
* Serializes the value before it will be stored in the actual cache backend.
* This method will be called if {@link autoSerialize} is set to true. Child classes may override this method to change
* the way the value is being serialized. The default implementation simply makes use of the PHP serialize() function
* unless {@link useIgbinarySerializer} is set to true and the igbinary extension is installed.
* Make sure to override {@link unserializeValue()} as well if you want to change the serialization process.
* @param mixed $value the unserialized representation of the value
* @return string the serialized representation of the value
* @since 1.1.11
**/
protected function serializeValue($value)
{
if ($this->useIgbinarySerializer) {
return igbinary_serialize($value);
}
return serialize($value);
}
/**
* Unserializes the value after it was retrieved from the actual cache backend.
* This method will be called if {@link autoSerialize} is set to true. Child classes may override this method to change
* the way the value is being unserialized. The default implementation simply makes use of the PHP unserialize() function
* unless {@link useIgbinarySerializer} is set to true and the igbinary extension is installed.
* Make sure to override {@link serializeValue()} as well if you want to change the serialization process.
* @param string $value the serialized representation of the value
* @return mixed the unserialized representation of the value
* @since 1.1.11
**/
protected function unserializeValue($value)
{
if ($this->useIgbinarySerializer) {
return igbinary_unserialize($value);
}
return unserialize($value);
}
/**
* Returns whether there is a cache entry with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return boolean
*/
public function offsetExists($id)
{
return $this->get($id) !== false;
}
/**
* Retrieves the value from cache with a specified key.
* This method is required by the interface ArrayAccess.
* @param string $id a key identifying the cached value
* @return mixed the value stored in cache, false if the value is not in the cache or expired.
*/
public function offsetGet($id)
{
return $this->get($id);
}
/**
* Stores the value identified by a key into cache.
* If the cache already contains such a key, the existing value will be
* replaced with the new ones. To add expiration and dependencies, use the set() method.
* This method is required by the interface ArrayAccess.
* @param string $id the key identifying the value to be cached
* @param mixed $value the value to be cached
*/
public function offsetSet($id, $value)
{
$this->set($id, $value);
}
/**
* Deletes the value with the specified key from cache
* This method is required by the interface ArrayAccess.
* @param string $id the key of the value to be deleted
* @return boolean if no error happens during deletion
*/
public function offsetUnset($id)
{
$this->delete($id);
}
}