sharedmemory/lib/lfu.js

Cluster Shared Memory

/* Todo

  record = {
    key, value, count, expire
  }

  used = {
    0: {
      key: record,
      key: record
    },
    1: {
      ...
    }
  };

  usedLength = {
    0: 10,
    1: 11,
    3: 100
  };

  usedTail = 0;

  expire = linkedlist;

*/


var LinkedList = require('./linkedlist');

var CacheLRU = function(config) {
    
  var self = this;

  LinkedList.call(self);

  config = config || {};

  // default -> 30min | number | undefined => closed
  self.__expire__ = config.expire == 'default' ? 30 * 60 * 1000 : config.expire;

  // 记录数上限
  self.__max__ = config.max || 10000;

  // 统计
  self.__total__ = 0;
  self.__miss__ = 0;
  self.__hit__ = 0;

  // 根据记录数排序的队列
  self.__used__ = {};
  self.__usedLen__ = {};

};

CacheLRU.prototype = new LinkedList;

CacheLRU.prototype.set = function(key, value) {

    if (typeof value == 'undefined') {
        this.remove(key);
    }

    var self = this;
    var __list__ = self.__list__;
    var record = __list__[key];

    if (!record) {

        record = {
            key: key,
            value: value,
            count: 0
        };

    } else {
        
        record.value = value;
        record.count += 1;
        this.remove(key);

    }

    if (self.__expire__) {
      record.deadline = Date.now() + self.defaultExpire;
    }

    this.unshift(record);

};

Cache.prototype.get = function(key) {

    var value;
    var record = this.__list__[key];

    if (record) {

        if (record.deadline) {
          var now = Date.now();
          if (record.deadline < now) {
            this.remove(key);
          } else {
            record.deadline = now + this.defaultExpire;
            record.count += 1;
            value = record.value;
            this.remove(key);
            this.__list__[key] = record;
            this.unshift(record);            
          }          
        } else {
          record.count += 1;
          value = record.value;
          this.remove(key);
          this.__list__[key] = record;
          this.unshift(record);  
        }

    }

    return value;

};

Cache.prototype.usedSet = function(record, oldIndex) {

  var self = this;
  var __used__ = self.__used__;
  var __usedLen__ = self.__usedLen__;

  var isNew = typeof oldIndex == 'undefined';



};