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// Simple LRU cache use doubly linked list
// @module zrender/core/LRU
define(function(require) {
/**
* Simple double linked list. Compared with array, it has O(1) remove operation.
* @constructor
*/
var LinkedList = function() {
/**
* @type {module:zrender/core/LRU~Entry}
*/
this.head = null;
/**
* @type {module:zrender/core/LRU~Entry}
*/
this.tail = null;
this._len = 0;
};
var linkedListProto = LinkedList.prototype;
/**
* Insert a new value at the tail
* @param {} val
* @return {module:zrender/core/LRU~Entry}
*/
linkedListProto.insert = function(val) {
var entry = new Entry(val);
this.insertEntry(entry);
return entry;
};
/**
* Insert an entry at the tail
* @param {module:zrender/core/LRU~Entry} entry
*/
linkedListProto.insertEntry = function(entry) {
if (!this.head) {
this.head = this.tail = entry;
}
else {
this.tail.next = entry;
entry.prev = this.tail;
this.tail = entry;
}
this._len++;
};
/**
* Remove entry.
* @param {module:zrender/core/LRU~Entry} entry
*/
linkedListProto.remove = function(entry) {
var prev = entry.prev;
var next = entry.next;
if (prev) {
prev.next = next;
}
else {
// Is head
this.head = next;
}
if (next) {
next.prev = prev;
}
else {
// Is tail
this.tail = prev;
}
entry.next = entry.prev = null;
this._len--;
};
/**
* @return {number}
*/
linkedListProto.len = function() {
return this._len;
};
/**
* @constructor
* @param {} val
*/
var Entry = function(val) {
/**
* @type {}
*/
this.value = val;
/**
* @type {module:zrender/core/LRU~Entry}
*/
this.next;
/**
* @type {module:zrender/core/LRU~Entry}
*/
this.prev;
};
/**
* LRU Cache
* @constructor
* @alias module:zrender/core/LRU
*/
var LRU = function(maxSize) {
this._list = new LinkedList();
this._map = {};
this._maxSize = maxSize || 10;
};
var LRUProto = LRU.prototype;
/**
* @param {string} key
* @param {} value
*/
LRUProto.put = function(key, value) {
var list = this._list;
var map = this._map;
if (map[key] == null) {
var len = list.len();
if (len >= this._maxSize && len > 0) {
// Remove the least recently used
var leastUsedEntry = list.head;
list.remove(leastUsedEntry);
delete map[leastUsedEntry.key];
}
var entry = list.insert(value);
entry.key = key;
map[key] = entry;
}
};
/**
* @param {string} key
* @return {}
*/
LRUProto.get = function(key) {
var entry = this._map[key];
var list = this._list;
if (entry != null) {
// Put the latest used entry in the tail
if (entry !== list.tail) {
list.remove(entry);
list.insertEntry(entry);
}
return entry.value;
}
};
/**
* Clear the cache
*/
LRUProto.clear = function() {
this._list.clear();
this._map = {};
};
return LRU;
});
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