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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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