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413 lines
9.5 KiB
413 lines
9.5 KiB
// Load modules
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var Dgram = require('dgram');
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var Dns = require('dns');
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var Hoek = require('hoek');
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// Declare internals
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var internals = {};
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exports.time = function (options, callback) {
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if (arguments.length !== 2) {
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callback = arguments[0];
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options = {};
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}
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var settings = Hoek.clone(options);
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settings.host = settings.host || 'pool.ntp.org';
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settings.port = settings.port || 123;
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settings.resolveReference = settings.resolveReference || false;
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// Declare variables used by callback
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var timeoutId = 0;
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var sent = 0;
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// Ensure callback is only called once
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var finish = function (err, result) {
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if (timeoutId) {
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clearTimeout(timeoutId);
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timeoutId = 0;
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}
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socket.removeAllListeners();
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socket.once('error', internals.ignore);
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socket.close();
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return callback(err, result);
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};
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finish = Hoek.once(finish);
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// Create UDP socket
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var socket = Dgram.createSocket('udp4');
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socket.once('error', function (err) {
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return finish(err);
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});
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// Listen to incoming messages
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socket.on('message', function (buffer, rinfo) {
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var received = Date.now();
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var message = new internals.NtpMessage(buffer);
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if (!message.isValid) {
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return finish(new Error('Invalid server response'), message);
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}
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if (message.originateTimestamp !== sent) {
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return finish(new Error('Wrong originate timestamp'), message);
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}
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// Timestamp Name ID When Generated
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// ------------------------------------------------------------
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// Originate Timestamp T1 time request sent by client
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// Receive Timestamp T2 time request received by server
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// Transmit Timestamp T3 time reply sent by server
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// Destination Timestamp T4 time reply received by client
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//
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// The roundtrip delay d and system clock offset t are defined as:
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//
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// d = (T4 - T1) - (T3 - T2) t = ((T2 - T1) + (T3 - T4)) / 2
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var T1 = message.originateTimestamp;
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var T2 = message.receiveTimestamp;
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var T3 = message.transmitTimestamp;
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var T4 = received;
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message.d = (T4 - T1) - (T3 - T2);
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message.t = ((T2 - T1) + (T3 - T4)) / 2;
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message.receivedLocally = received;
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if (!settings.resolveReference ||
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message.stratum !== 'secondary') {
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return finish(null, message);
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}
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// Resolve reference IP address
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Dns.reverse(message.referenceId, function (err, domains) {
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if (/* $lab:coverage:off$ */ !err /* $lab:coverage:on$ */) {
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message.referenceHost = domains[0];
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}
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return finish(null, message);
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});
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});
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// Set timeout
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if (settings.timeout) {
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timeoutId = setTimeout(function () {
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timeoutId = 0;
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return finish(new Error('Timeout'));
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}, settings.timeout);
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}
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// Construct NTP message
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var message = new Buffer(48);
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for (var i = 0; i < 48; i++) { // Zero message
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message[i] = 0;
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}
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message[0] = (0 << 6) + (4 << 3) + (3 << 0) // Set version number to 4 and Mode to 3 (client)
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sent = Date.now();
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internals.fromMsecs(sent, message, 40); // Set transmit timestamp (returns as originate)
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// Send NTP request
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socket.send(message, 0, message.length, settings.port, settings.host, function (err, bytes) {
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if (err ||
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bytes !== 48) {
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return finish(err || new Error('Could not send entire message'));
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}
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});
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};
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internals.NtpMessage = function (buffer) {
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this.isValid = false;
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// Validate
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if (buffer.length !== 48) {
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return;
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}
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// Leap indicator
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var li = (buffer[0] >> 6);
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switch (li) {
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case 0: this.leapIndicator = 'no-warning'; break;
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case 1: this.leapIndicator = 'last-minute-61'; break;
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case 2: this.leapIndicator = 'last-minute-59'; break;
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case 3: this.leapIndicator = 'alarm'; break;
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}
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// Version
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var vn = ((buffer[0] & 0x38) >> 3);
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this.version = vn;
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// Mode
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var mode = (buffer[0] & 0x7);
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switch (mode) {
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case 1: this.mode = 'symmetric-active'; break;
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case 2: this.mode = 'symmetric-passive'; break;
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case 3: this.mode = 'client'; break;
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case 4: this.mode = 'server'; break;
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case 5: this.mode = 'broadcast'; break;
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case 0:
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case 6:
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case 7: this.mode = 'reserved'; break;
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}
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// Stratum
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var stratum = buffer[1];
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if (stratum === 0) {
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this.stratum = 'death';
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}
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else if (stratum === 1) {
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this.stratum = 'primary';
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}
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else if (stratum <= 15) {
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this.stratum = 'secondary';
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}
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else {
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this.stratum = 'reserved';
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}
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// Poll interval (msec)
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this.pollInterval = Math.round(Math.pow(2, buffer[2])) * 1000;
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// Precision (msecs)
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this.precision = Math.pow(2, buffer[3]) * 1000;
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// Root delay (msecs)
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var rootDelay = 256 * (256 * (256 * buffer[4] + buffer[5]) + buffer[6]) + buffer[7];
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this.rootDelay = 1000 * (rootDelay / 0x10000);
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// Root dispersion (msecs)
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this.rootDispersion = ((buffer[8] << 8) + buffer[9] + ((buffer[10] << 8) + buffer[11]) / Math.pow(2, 16)) * 1000;
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// Reference identifier
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this.referenceId = '';
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switch (this.stratum) {
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case 'death':
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case 'primary':
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this.referenceId = String.fromCharCode(buffer[12]) + String.fromCharCode(buffer[13]) + String.fromCharCode(buffer[14]) + String.fromCharCode(buffer[15]);
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break;
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case 'secondary':
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this.referenceId = '' + buffer[12] + '.' + buffer[13] + '.' + buffer[14] + '.' + buffer[15];
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break;
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}
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// Reference timestamp
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this.referenceTimestamp = internals.toMsecs(buffer, 16);
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// Originate timestamp
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this.originateTimestamp = internals.toMsecs(buffer, 24);
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// Receive timestamp
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this.receiveTimestamp = internals.toMsecs(buffer, 32);
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// Transmit timestamp
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this.transmitTimestamp = internals.toMsecs(buffer, 40);
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// Validate
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if (this.version === 4 &&
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this.stratum !== 'reserved' &&
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this.mode === 'server' &&
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this.originateTimestamp &&
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this.receiveTimestamp &&
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this.transmitTimestamp) {
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this.isValid = true;
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}
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return this;
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};
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internals.toMsecs = function (buffer, offset) {
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var seconds = 0;
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var fraction = 0;
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for (var i = 0; i < 4; ++i) {
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seconds = (seconds * 256) + buffer[offset + i];
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}
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for (i = 4; i < 8; ++i) {
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fraction = (fraction * 256) + buffer[offset + i];
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}
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return ((seconds - 2208988800 + (fraction / Math.pow(2, 32))) * 1000);
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};
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internals.fromMsecs = function (ts, buffer, offset) {
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var seconds = Math.floor(ts / 1000) + 2208988800;
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var fraction = Math.round((ts % 1000) / 1000 * Math.pow(2, 32));
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buffer[offset + 0] = (seconds & 0xFF000000) >> 24;
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buffer[offset + 1] = (seconds & 0x00FF0000) >> 16;
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buffer[offset + 2] = (seconds & 0x0000FF00) >> 8;
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buffer[offset + 3] = (seconds & 0x000000FF);
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buffer[offset + 4] = (fraction & 0xFF000000) >> 24;
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buffer[offset + 5] = (fraction & 0x00FF0000) >> 16;
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buffer[offset + 6] = (fraction & 0x0000FF00) >> 8;
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buffer[offset + 7] = (fraction & 0x000000FF);
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};
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// Offset singleton
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internals.last = {
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offset: 0,
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expires: 0,
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host: '',
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port: 0
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};
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exports.offset = function (options, callback) {
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if (arguments.length !== 2) {
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callback = arguments[0];
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options = {};
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}
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var now = Date.now();
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var clockSyncRefresh = options.clockSyncRefresh || 24 * 60 * 60 * 1000; // Daily
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if (internals.last.offset &&
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internals.last.host === options.host &&
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internals.last.port === options.port &&
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now < internals.last.expires) {
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process.nextTick(function () {
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callback(null, internals.last.offset);
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});
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return;
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}
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exports.time(options, function (err, time) {
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if (err) {
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return callback(err, 0);
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}
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internals.last = {
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offset: Math.round(time.t),
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expires: now + clockSyncRefresh,
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host: options.host,
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port: options.port
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};
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return callback(null, internals.last.offset);
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});
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};
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// Now singleton
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internals.now = {
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intervalId: 0
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};
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exports.start = function (options, callback) {
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if (arguments.length !== 2) {
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callback = arguments[0];
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options = {};
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}
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if (internals.now.intervalId) {
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process.nextTick(function () {
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callback();
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});
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return;
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}
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exports.offset(options, function (err, offset) {
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internals.now.intervalId = setInterval(function () {
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exports.offset(options, function () { });
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}, options.clockSyncRefresh || 24 * 60 * 60 * 1000); // Daily
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return callback();
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});
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};
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exports.stop = function () {
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if (!internals.now.intervalId) {
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return;
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}
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clearInterval(internals.now.intervalId);
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internals.now.intervalId = 0;
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};
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exports.isLive = function () {
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return !!internals.now.intervalId;
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};
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exports.now = function () {
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var now = Date.now();
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if (!exports.isLive() ||
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now >= internals.last.expires) {
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return now;
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}
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return now + internals.last.offset;
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};
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internals.ignore = function () {
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};
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