mirror of https://github.com/jkjoy/sunpeiwen.git
117 lines
2.1 KiB
JavaScript
117 lines
2.1 KiB
JavaScript
/**
|
|
* Module dependencies.
|
|
*/
|
|
|
|
var crypto = require('crypto')
|
|
, nodes = require('../nodes');
|
|
|
|
var MemoryCache = module.exports = function(options) {
|
|
options = options || {};
|
|
this.limit = options['cache limit'] || 256;
|
|
this._cache = {};
|
|
this.length = 0;
|
|
this.head = this.tail = null;
|
|
};
|
|
|
|
/**
|
|
* Set cache item with given `key` to `value`.
|
|
*
|
|
* @param {String} key
|
|
* @param {Object} value
|
|
* @api private
|
|
*/
|
|
|
|
MemoryCache.prototype.set = function(key, value) {
|
|
var clone = value.clone()
|
|
, item;
|
|
|
|
clone.filename = nodes.filename;
|
|
clone.lineno = nodes.lineno;
|
|
clone.column = nodes.column;
|
|
item = { key: key, value: clone };
|
|
this._cache[key] = item;
|
|
|
|
if (this.tail) {
|
|
this.tail.next = item;
|
|
item.prev = this.tail;
|
|
} else {
|
|
this.head = item;
|
|
}
|
|
|
|
this.tail = item;
|
|
if (this.length++ == this.limit) this.purge();
|
|
};
|
|
|
|
/**
|
|
* Get cache item with given `key`.
|
|
*
|
|
* @param {String} key
|
|
* @return {Object}
|
|
* @api private
|
|
*/
|
|
|
|
MemoryCache.prototype.get = function(key) {
|
|
var item = this._cache[key]
|
|
, val = item.value.clone();
|
|
|
|
if (item == this.tail) return val;
|
|
if (item.next) {
|
|
if (item == this.head) this.head = item.next;
|
|
item.next.prev = item.prev;
|
|
}
|
|
if (item.prev) item.prev.next = item.next;
|
|
|
|
item.next = null;
|
|
item.prev = this.tail;
|
|
|
|
if (this.tail) this.tail.next = item;
|
|
this.tail = item;
|
|
|
|
return val;
|
|
};
|
|
|
|
/**
|
|
* Check if cache has given `key`.
|
|
*
|
|
* @param {String} key
|
|
* @return {Boolean}
|
|
* @api private
|
|
*/
|
|
|
|
MemoryCache.prototype.has = function(key) {
|
|
return !!this._cache[key];
|
|
};
|
|
|
|
/**
|
|
* Generate key for the source `str` with `options`.
|
|
*
|
|
* @param {String} str
|
|
* @param {Object} options
|
|
* @return {String}
|
|
* @api private
|
|
*/
|
|
|
|
MemoryCache.prototype.key = function(str, options) {
|
|
var hash = crypto.createHash('sha1');
|
|
hash.update(str + options.prefix);
|
|
return hash.digest('hex');
|
|
};
|
|
|
|
/**
|
|
* Remove the oldest item from the cache.
|
|
*
|
|
* @api private
|
|
*/
|
|
|
|
MemoryCache.prototype.purge = function() {
|
|
var item = this.head;
|
|
|
|
if (this.head.next) {
|
|
this.head = this.head.next;
|
|
this.head.prev = null;
|
|
}
|
|
|
|
this._cache[item.key] = item.prev = item.next = null;
|
|
this.length--;
|
|
};
|