116 lines
2.3 KiB
JavaScript
116 lines
2.3 KiB
JavaScript
/*!
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* timedata.js - time management for bcoin
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* Copyright (c) 2014-2015, Fedor Indutny (MIT License)
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* Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
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* https://github.com/bcoin-org/bcoin
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*/
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'use strict';
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var utils = require('../utils/utils');
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var EventEmitter = require('events').EventEmitter;
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/**
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* An object which handles "adjusted time". This may not
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* look it, but this is actually a semi-consensus-critical
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* piece of code. It handles version packets from peers
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* and calculates what to offset our system clock's time by.
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* @exports TimeData
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* @constructor
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* @param {Number} [limit=200]
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* @property {Array} samples
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* @property {Object} known
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* @property {Number} limit
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* @property {Number} offset
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*/
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function TimeData(limit) {
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if (!(this instanceof TimeData))
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return new TimeData(limit);
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EventEmitter.call(this);
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if (limit == null)
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limit = 200;
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this.samples = [];
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this.known = {};
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this.limit = limit;
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this.offset = 0;
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this._checked = false;
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}
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utils.inherits(TimeData, EventEmitter);
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/**
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* Add time data.
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* @param {String} host
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* @param {Number} time
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*/
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TimeData.prototype.add = function add(host, time) {
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var sample = time - utils.now();
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var i, median, match, offset;
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if (this.samples.length >= this.limit)
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return;
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if (this.known[host] != null)
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return;
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this.known[host] = sample;
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utils.binaryInsert(this.samples, sample, compare);
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this.emit('sample', sample, this.samples.length);
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if (this.samples.length >= 5 && this.samples.length % 2 === 1) {
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median = this.samples[this.samples / 2 | 0];
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if (Math.abs(median) < 70 * 60) {
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this.offset = median;
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} else {
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this.offset = 0;
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if (!this._checked) {
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match = false;
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for (i = 0; i < this.samples.length; i++) {
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offset = this.samples[i];
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if (offset !== 0 && Math.abs(offset) < 5 * 60) {
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match = true;
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break;
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}
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}
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if (!match) {
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this._checked = true;
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this.emit('mismatch');
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}
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}
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}
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this.emit('offset', this.offset);
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}
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};
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/**
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* Get the current adjusted time.
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* @returns {Number} Adjusted Time.
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*/
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TimeData.prototype.now = function now() {
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return utils.now() + this.offset;
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};
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/*
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* Helpers
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*/
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function compare(a, b) {
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return a - b;
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}
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/*
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* Expose
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*/
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module.exports = TimeData;
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