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/**
* 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--;
};
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