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<?php
/**
* Least Recently Used Cache
*
* A fixed sized cache that removes the element used last when it reaches its
* size limit.
*
* Based on https://github.com/cash/LRUCache
*
* @access private
*
* @package Elgg.Core
* @subpackage Cache
*/
class ElggLRUCache implements ArrayAccess {
/** @var int */
protected $maximumSize;
/**
* The front of the array contains the LRU element
*
* @var array
*/
protected $data = array();
/**
* Create a LRU Cache
*
* @param int $size The size of the cache
* @throws InvalidArgumentException
*/
public function __construct($size) {
if (!is_int($size) || $size <= 0) {
throw new InvalidArgumentException();
}
$this->maximumSize = $size;
}
/**
* Get the value cached with this key
*
* @param int|string $key The key. Strings that are ints are cast to ints.
* @param mixed $default The value to be returned if key not found. (Optional)
* @return mixed
*/
public function get($key, $default = null) {
if (isset($this->data[$key])) {
$this->recordAccess($key);
return $this->data[$key];
} else {
return $default;
}
}
/**
* Add something to the cache
*
* @param int|string $key The key. Strings that are ints are cast to ints.
* @param mixed $value The value to cache
* @return void
*/
public function set($key, $value) {
if (isset($this->data[$key])) {
$this->data[$key] = $value;
$this->recordAccess($key);
} else {
$this->data[$key] = $value;
if ($this->size() > $this->maximumSize) {
// remove least recently used element (front of array)
reset($this->data);
unset($this->data[key($this->data)]);
}
}
}
/**
* Get the number of elements in the cache
*
* @return int
*/
public function size() {
return count($this->data);
}
/**
* Does the cache contain an element with this key
*
* @param int|string $key The key
* @return boolean
*/
public function containsKey($key) {
return isset($this->data[$key]);
}
/**
* Remove the element with this key.
*
* @param int|string $key The key
* @return mixed Value or null if not set
*/
public function remove($key) {
if (isset($this->data[$key])) {
$value = $this->data[$key];
unset($this->data[$key]);
return $value;
} else {
return null;
}
}
/**
* Clear the cache
*
* @return void
*/
public function clear() {
$this->data = array();
}
/**
* Moves the element from current position to end of array
*
* @param int|string $key The key
* @return void
*/
protected function recordAccess($key) {
$value = $this->data[$key];
unset($this->data[$key]);
$this->data[$key] = $value;
}
/**
* Assigns a value for the specified key
*
* @see ArrayAccess::offsetSet()
*
* @param int|string $key The key to assign the value to.
* @param mixed $value The value to set.
* @return void
*/
public function offsetSet($key, $value) {
$this->set($key, $value);
}
/**
* Get the value for specified key
*
* @see ArrayAccess::offsetGet()
*
* @param int|string $key The key to retrieve.
* @return mixed
*/
public function offsetGet($key) {
return $this->get($key);
}
/**
* Unsets a key.
*
* @see ArrayAccess::offsetUnset()
*
* @param int|string $key The key to unset.
* @return void
*/
public function offsetUnset($key) {
$this->remove($key);
}
/**
* Does key exist?
*
* @see ArrayAccess::offsetExists()
*
* @param int|string $key A key to check for.
* @return boolean
*/
public function offsetExists($key) {
return $this->containsKey($key);
}
}
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