ntp-packet-parser/dist/NtpPacketParser.js

A parser for NTP UDP packets

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