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‎.babelrc

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{
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"presets": ["es2015"]
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}

‎.gitignore

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node_modules
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dist

‎.npmignore

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/index.js

‎.travis.yml

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language: node_js
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cache:
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yarn: true
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directories:
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- node_modules
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script: yarn test

‎README.md

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![NPM downloads](https://img.shields.io/npm/dt/ntp-packet-parser.svg)
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![Travis](https://img.shields.io/travis/buffcode/npm-packet-parser.svg)
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![GitHub release](https://img.shields.io/github/release/buffcode/npm-packet-parser.svg)
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![Dependencies](https://img.shields.io/david/buffcode/npm-packet-parser.svg)
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# NTP packet parser
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Library to parse NTP response packets according to [RFC 5905](https://www.ietf.org/rfc/rfc5905.txt) into a easy-to-use structure.
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It does not apply any validations or calculations regarding the time but solely parses the data.
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## Installation
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```bash
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yarn add ntp-packet-parser
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```
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## Usage
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### ES6 style
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```js
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import NtpPacketParser from "ntp-packet-parser";
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/** const udpPacket = new Buffer(...); **/
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const result = NtpPacketParser.parse(udpPacket);
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```
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### Legacy style
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```js
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var NtpPacketParser = require("ntp-packet-parser");
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/** const udpPacket = new Buffer(...); **/
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var result = NtpPacketParser.parse(udpPacket);
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```
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## Structure
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The response from `NtpPacketParser.parse` will always return the following object structure:
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| Property | Type | Description |
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| :--- | :--- | :--- |
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| leapIndicator | `Integer` | Warning of an impending leap second to be inserted or deleted in the last minute of the current month |
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| version | `Integer` | NTP version number, currently 4 |
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| mode | `Integer` | Request/response mode |
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| stratum | `Integer` | Stratum of the server |
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| poll | `Integer` | Integer representing the maximum interval between successive messages (Note: you need to apply `Math.log2` to get the real value) |
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| precision | `Integer` | Integer representing the precision of the system clock (Note: you need to apply `Math.log2` to get the real value) |
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| rootDelay | `Date` | Total round-trip delay to the reference clock |
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| rootDispersion | `Date` | Total dispersion to the reference clock |
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| referenceId | `String` | String to identify the particular server or reference clock |
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| referenceTimestamp | `Date` | Time when the system clock was last set or corrected |
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| originTimestamp | `Date` | Time at the client when the request departed for the server |
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| receiveTimestamp | `Date` | Time at the server when the request arrived from the client |
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| transmitTimestamp | `Date` | Time at the server when the response left for the client |
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To get the relative time for any Date property, calculate the difference between "Jan 01 1900 GMT" and the given date.
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```js
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let rootDelayInMilliseconds = result.rootDelay.getTime() - new Date("Jan 01 1900 GMT").getTime();
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```
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For further explanations on the possible values of these properties please refer to [RFC 5909](https://www.ietf.org/rfc/rfc5905.txt), Page 19ff.
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## Testing
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Some tests regarding structure, response and error handling exist. To run them locally:
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```js
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yarn test
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```
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## Contributing
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Please file a PR against `master`.
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## License
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[GNU General Public License Version 3](LICENSE)

‎index.js

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"use strict";
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/**
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* @typedef {Object} NTPPacket
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* @property {int} leapIndicator
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* @property {int} version
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* @property {int} mode
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* @property {int} stratum
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* @property {int} poll
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* @property {int} precision
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* @property {Date} rootDelay
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* @property {Date} rootDispersion
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* @property {String} referenceId
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* @property {Date} referenceTimestamp
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* @property {Date} originTimestamp
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* @property {Date} receiveTimestamp
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* @property {Date} transmitTimestamp
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*/
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export default class NtpPacketParser {
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/**
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* Returns the structure of the UDP packet for parsing
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* @returns {Object}
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*/
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static get packetStruct() {
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return [
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{ name: "leapIndicator", bits: 2 },
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{ name: "version", bits: 3 },
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{ name: "mode", bits: 3 },
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{ name: "stratum", bits: 8 },
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{ name: "poll", bits: 8 },
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{ name: "precision", bits: 8 },
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{
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name: "rootDelay",
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bits: 32,
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converter: NtpPacketParser._fromNtpTimestamp
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},
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{
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name: "rootDispersion",
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bits: 32,
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converter: NtpPacketParser._fromNtpTimestamp
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},
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{
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name: "referenceId",
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bits: 32,
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converter: (v, s) => this._ntpIdentifier(s.stratum, v)
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},
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{
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name: "referenceTimestamp",
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bits: 64,
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converter: NtpPacketParser._fromNtpTimestamp
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},
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{
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name: "originTimestamp",
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bits: 64,
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converter: NtpPacketParser._fromNtpTimestamp
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},
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{
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name: "receiveTimestamp",
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bits: 64,
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converter: NtpPacketParser._fromNtpTimestamp
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},
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{
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name: "transmitTimestamp",
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bits: 64,
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converter: NtpPacketParser._fromNtpTimestamp
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}
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];
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}
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/**
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* Returns the selected bits in binary notation
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* @param msg
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* @param {int} start
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* @param {int} length
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* @returns {string} Bits in binary notation
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* @private
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*/
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static _getBits(msg, start, length) {
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let bits = "";
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const pad = "00000000";
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for (let i = 0; i < msg.length; i++) {
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let bitsUnpadded = (msg[i] >>> 0).toString(2);
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bits += pad.substring(0, pad.length - bitsUnpadded.length) + bitsUnpadded;
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}
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return bits.slice(start, start + length);
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}
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/**
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* Converts a NTP identifier from binary notation to ASCII
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* @param {int} stratum
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* @param {String} value Bits in binary notation
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* @returns {string}
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* @private
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*/
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static _ntpIdentifier(stratum, value) {
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if (stratum != 1) {
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return parseInt(value, 2).toString();
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}
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let chars = [
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value.slice(0, 8),
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value.slice(8, 16),
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value.slice(16, 24),
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value.slice(24, 32)
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];
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chars = chars.map(function(v) {
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return String.fromCharCode(parseInt(v, 2));
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});
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return chars.join("").replace(/\0+$/, "");
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}
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/**
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* Converts a NTP timestamp from binary notation to a Date object
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* @param {String} value Bits in binary notation
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* @returns {Date}
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* @private
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*/
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static _fromNtpTimestamp(value) {
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if (value.length % 2 !== 0) {
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throw new Error(
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"Invalid timestamp format, expected even number of characters"
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);
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}
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const seconds = parseInt(value, 2) / Math.pow(2, value.length / 2),
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date = new Date("Jan 01 1900 GMT");
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date.setUTCMilliseconds(date.getUTCMilliseconds() + seconds * 1000);
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return date;
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}
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/**
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* Parses an UDP packet buffer and returns a NTPPacket struct
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* @param {Buffer} udpPacket
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* @returns {NTPPacket}
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*/
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static parse(udpPacket) {
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let data = [];
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NtpPacketParser.packetStruct.forEach(item => {
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data[item.name] = undefined;
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});
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let offset = 0;
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NtpPacketParser.packetStruct.forEach(item => {
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data[item.name] = NtpPacketParser._getBits(udpPacket, offset, item.bits);
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if (item.converter) {
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data[item.name] = item.converter(data[item.name], data);
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} else {
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data[item.name] = parseInt(data[item.name], 2);
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}
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offset += item.bits;
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});
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return data;
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}
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}

‎package.json

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{
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"name": "ntp-packet-parser",
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"version": "0.1",
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"description": "A parser for NTP UDP packets",
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"main": "dist/index.js",
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"scripts": {
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"test": "mocha --compilers js:babel-core/register --recursive test",
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"build": "babel index.js --presets babel-preset-es2015 --out-dir dist && prettier --write dist/index.js",
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"prettier": "prettier --write index.js test/**/*.js test/**/*.json",
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"prettier:lint": "prettier --list-different index.js"
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},
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"keywords": [
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"ntp",
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"clock",
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"sync",
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"parser",
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"udp"
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],
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"author": "Laurens Stötzel",
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"repository": {
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"type": "git",
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"url": "https://github.com/buffcode/ntp-packet-parser.git"
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},
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"devDependencies": {
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"babel-cli": "6",
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"babel-preset-es2015": "6",
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"mocha": "^3.5.0",
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"prettier": "^1.6.1"
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}
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}

‎test/packets.valid.js

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module.exports = [
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{
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buffer: [
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28,
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1,
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48,
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234,
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0,
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0,
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0,
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0,
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0,
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0,
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0,
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68,
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80,
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84,
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66,
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0,
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221,
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82,
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40,
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120,
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122,
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239,
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46,
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145,
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48,
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48,
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48,
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48,
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48,
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48,
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48,
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10,
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221,
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82,
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40,
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124,
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17,
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15,
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55,
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20,
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221,
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82,
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40,
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124,
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17,
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25,
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203,
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213
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],
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expected: {
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leapIndicator: 0,
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version: 3,
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mode: 4,
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stratum: 1,
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poll: 48,
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precision: 234,
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rootDelay: new Date("1900-01-01T00:00:00.000Z"),
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rootDispersion: new Date("1900-01-01T00:00:00.001Z"),
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referenceId: "PTB",
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referenceTimestamp: new Date("2017-08-31T06:17:28.480Z"),
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originTimestamp: new Date("1925-08-15T05:27:12.188Z"),
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receiveTimestamp: new Date("2017-08-31T06:17:32.066Z"),
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transmitTimestamp: new Date("2017-08-31T06:17:32.066Z")
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}
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}
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];

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