Craig Rowe
76 linhas
2.0 KiB
JavaScript
76 linhas
2.0 KiB
JavaScript
var Stream = require('stream').Stream;
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var util = require('util');
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var dgram = require('dgram');
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var constants = require('../constants');
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var parseNavdata = require('./parseNavdata');
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module.exports = UdpNavdataStream;
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util.inherits(UdpNavdataStream, Stream);
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function UdpNavdataStream(options) {
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Stream.call(this);
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options = options || {};
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this.readable = true;
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this._socket = options.socket || dgram.createSocket('udp4');
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this._port = options.port || constants.ports.NAVDATA;
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this._ip = options.ip || constants.DEFAULT_DRONE_IP;
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this._initialized = false;
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this._parseNavdata = options.parser || parseNavdata;
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this._timeout = options.timeout || 100;
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this._timer = undefined;
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this._sequenceNumber = 0;
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}
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UdpNavdataStream.prototype.resume = function() {
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if (!this._initialized) {
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this._init();
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this._initialized = true;
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}
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this._requestNavdata();
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};
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UdpNavdataStream.prototype.destroy = function() {
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this._socket.close();
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};
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UdpNavdataStream.prototype._init = function() {
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this._socket.bind();
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this._socket.on('message', this._handleMessage.bind(this));
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};
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UdpNavdataStream.prototype._requestNavdata = function() {
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var buffer = new Buffer([1]);
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this._socket.send(buffer, 0, buffer.length, this._port, this._ip);
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this._setTimeout();
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// @TODO logging
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};
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UdpNavdataStream.prototype._setTimeout = function() {
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clearTimeout(this._timer);
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this._timer = setTimeout(this._requestNavdata.bind(this), this._timeout);
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};
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UdpNavdataStream.prototype._handleMessage = function(buffer) {
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try {
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var navdata = this._parseNavdata(buffer);
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} catch (err) {
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// avoid 'error' causing an exception when nobody is listening
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if (this.listeners('error').length > 0) {
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this.emit('error', err);
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}
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return;
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}
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// Ignore out of order messages
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if (navdata.sequenceNumber > this._sequenceNumber) {
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this._sequenceNumber = navdata.sequenceNumber;
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this.emit('data', navdata);
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}
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this._setTimeout();
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};
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