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<?php |
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namespace CHMLib\LZX; |
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use Exception; |
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/** |
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* Handle the cache of recently used data. |
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*/ |
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class LRUCache |
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{ |
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/** |
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* The cached items. |
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* |
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* @var LRUCacheItem[] |
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*/ |
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protected $cache; |
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/** |
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* The maximim capacity of the cache. |
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* |
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* @var int |
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*/ |
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protected $capacity; |
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/** |
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* Initializes the instance. |
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* |
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* @param int $capacity The maximim capacity of the cache. |
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* |
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* @throws Exception Throws an Exception in case of errors. |
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*/ |
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public function __construct($capacity) |
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{ |
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$this->capacity = (int) $capacity; |
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if ($this->capacity < 1) { |
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throw new Exception('The cache capacity must be greather than zero'); |
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} |
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$this->cache = array(); |
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} |
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/** |
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* Get a cached items given its key (return null if no cached items with the specified key). |
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* |
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* @param mixed $key |
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* |
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* @return mixed|null |
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*/ |
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public function get($key) |
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{ |
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$result = null; |
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if (isset($this->cache[$key])) { |
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$item = $this->cache[$key]; |
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array_map( |
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function (LRUCacheItem $i) { |
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--$i->hits; |
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}, |
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$this->cache |
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); |
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$item->hits += 2; |
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$result = $item->value; |
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} |
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return $result; |
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} |
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/** |
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* Ensure that the cache has at least one empty slot (it the cache is full, we'll remove the less used cache item). |
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* |
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* @return null|mixed Returns null if no item has been removed, otherwise returns the value of the removed item. |
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*/ |
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public function prune() |
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{ |
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$result = null; |
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if (count($this->cache) >= $this->capacity) { |
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$kick = null; |
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$kickKey = null; |
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foreach ($this->cache as $key => $item) { |
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if ($kick === null || $kick->hits > $item->hits) { |
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$kick = $item; |
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$kickKey = $key; |
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} |
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} |
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unset($this->cache[$kickKey]); |
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$result = $kick->value; |
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} |
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return $result; |
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} |
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/** |
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* Add a new item to the cache. |
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* |
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* @param mixed $key The key to assign to the cached item. |
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* @param mixed $value The value to be cached. |
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*/ |
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public function put($key, $value) |
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{ |
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if (!isset($this->cache[$key])) { |
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$this->prune(); |
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} |
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$this->cache[$key] = new LRUCacheItem($value); |
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} |
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/** |
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* Clear the cache. |
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*/ |
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public function clear() |
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{ |
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$this->cache = array(); |
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} |
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/** |
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* Get the number of the currently cached items. |
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* |
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* @return int |
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*/ |
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public function size() |
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{ |
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return count($this->cache); |
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} |
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} |
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mlocati /
chm-lib
