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index.js
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index.js
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var dgram = require('dgram');
var cyclist = require('cyclist');
var util = require('util');
var EventEmitter = require('events').EventEmitter;
var Duplex = require('stream').Duplex;
var bufferAlloc = require('buffer-alloc');
var EXTENSION = 0;
var VERSION = 1;
var UINT16 = 0xffff;
var ID_MASK = 0xf << 4;
var MTU = 1400;
var PACKET_DATA = 0 << 4;
var PACKET_FIN = 1 << 4;
var PACKET_STATE = 2 << 4;
var PACKET_RESET = 3 << 4;
var PACKET_SYN = 4 << 4;
var MIN_PACKET_SIZE = 20;
var DEFAULT_WINDOW_SIZE = 1 << 18;
var CLOSE_GRACE = 5000;
var BUFFER_SIZE = 512;
var uint32 = function(n) {
return n >>> 0;
};
var uint16 = function(n) {
return n & UINT16;
};
var timestamp = function() {
var offset = process.hrtime();
var then = Date.now() * 1000;
return function() {
var diff = process.hrtime(offset);
return uint32(then + 1000000 * diff[0] + ((diff[1] / 1000) | 0));
};
}();
var bufferToPacket = function(buffer) {
var packet = {};
packet.id = buffer[0] & ID_MASK;
packet.connection = buffer.readUInt16BE(2);
packet.timestamp = buffer.readUInt32BE(4);
packet.timediff = buffer.readUInt32BE(8);
packet.window = buffer.readUInt32BE(12);
packet.seq = buffer.readUInt16BE(16);
packet.ack = buffer.readUInt16BE(18);
packet.data = buffer.length > 20 ? buffer.slice(20) : null;
return packet;
};
var packetToBuffer = function(packet) {
var buffer = bufferAlloc(20 + (packet.data ? packet.data.length : 0));
buffer[0] = packet.id | VERSION;
buffer[1] = EXTENSION;
buffer.writeUInt16BE(packet.connection, 2);
buffer.writeUInt32BE(packet.timestamp, 4);
buffer.writeUInt32BE(packet.timediff, 8);
buffer.writeUInt32BE(packet.window, 12);
buffer.writeUInt16BE(packet.seq, 16);
buffer.writeUInt16BE(packet.ack, 18);
if (packet.data) packet.data.copy(buffer, 20);
return buffer;
};
var createPacket = function(connection, id, data) {
return {
id: id,
connection: id === PACKET_SYN ? connection._recvId : connection._sendId,
seq: connection._seq,
ack: connection._ack,
timestamp: timestamp(),
timediff: 0,
window: DEFAULT_WINDOW_SIZE,
data: data,
sent: 0
};
};
var Connection = function(port, host, socket, syn) {
Duplex.call(this);
var self = this;
this.port = port;
this.host = host;
this.socket = socket;
this._outgoing = cyclist(BUFFER_SIZE);
this._incoming = cyclist(BUFFER_SIZE);
this._closed = false;
this._inflightPackets = 0;
this._closed = false;
this._alive = false;
if (syn) {
this._connecting = false;
this._recvId = uint16(syn.connection+1);
this._sendId = syn.connection;
this._seq = (Math.random() * UINT16) | 0;
this._ack = syn.seq;
this._synack = createPacket(this, PACKET_STATE, null);
this._transmit(this._synack);
} else {
this._connecting = true;
this._recvId = 0; // tmp value for v8 opt
this._sendId = 0; // tmp value for v8 opt
this._seq = (Math.random() * UINT16) | 0;
this._ack = 0;
this._synack = null;
socket.on('listening', function() {
self._recvId = socket.address().port; // using the port gives us system wide clash protection
self._sendId = uint16(self._recvId + 1);
self._sendOutgoing(createPacket(self, PACKET_SYN, null));
});
socket.on('error', function(err) {
self.emit('error', err);
});
socket.bind();
}
var resend = setInterval(this._resend.bind(this), 500);
var keepAlive = setInterval(this._keepAlive.bind(this), 10*1000);
var tick = 0;
var closed = function() {
if (++tick === 2) self._closing();
};
var sendFin = function() {
if (self._connecting) return self.once('connect', sendFin);
self._sendOutgoing(createPacket(self, PACKET_FIN, null));
self.once('flush', closed);
};
this.once('finish', sendFin);
this.once('close', function() {
if (!syn) setTimeout(socket.close.bind(socket), CLOSE_GRACE);
clearInterval(resend);
clearInterval(keepAlive);
});
this.once('end', function() {
process.nextTick(closed);
});
};
util.inherits(Connection, Duplex);
Connection.prototype.setTimeout = function() {
// TODO: impl me
};
Connection.prototype.destroy = function() {
this.end();
};
Connection.prototype.address = function() {
return {port:this.port, address:this.host};
};
Connection.prototype._read = function() {
// do nothing...
};
Connection.prototype._write = function(data, enc, callback) {
if (this._connecting) return this._writeOnce('connect', data, enc, callback);
while (this._writable()) {
var payload = this._payload(data);
this._sendOutgoing(createPacket(this, PACKET_DATA, payload));
if (payload.length === data.length) return callback();
data = data.slice(payload.length);
}
this._writeOnce('flush', data, enc, callback);
};
Connection.prototype._writeOnce = function(event, data, enc, callback) {
this.once(event, function() {
this._write(data, enc, callback);
});
};
Connection.prototype._writable = function() {
return this._inflightPackets < BUFFER_SIZE-1;
};
Connection.prototype._payload = function(data) {
if (data.length > MTU) return data.slice(0, MTU);
return data;
};
Connection.prototype._resend = function() {
var offset = this._seq - this._inflightPackets;
var first = this._outgoing.get(offset);
if (!first) return;
var timeout = 500000;
var now = timestamp();
if (uint32(first.sent - now) < timeout) return;
for (var i = 0; i < this._inflightPackets; i++) {
var packet = this._outgoing.get(offset+i);
if (uint32(packet.sent - now) >= timeout) this._transmit(packet);
}
};
Connection.prototype._keepAlive = function() {
if (this._alive) return this._alive = false;
this._sendAck();
};
Connection.prototype._closing = function() {
if (this._closed) return;
this._closed = true;
process.nextTick(this.emit.bind(this, 'close'));
};
// packet handling
Connection.prototype._recvAck = function(ack) {
var offset = this._seq - this._inflightPackets;
var acked = uint16(ack - offset)+1;
if (acked >= BUFFER_SIZE) return; // sanity check
for (var i = 0; i < acked; i++) {
this._outgoing.del(offset+i);
this._inflightPackets--;
}
if (!this._inflightPackets) this.emit('flush');
};
Connection.prototype._recvIncoming = function(packet) {
if (this._closed) return;
if (packet.id === PACKET_SYN && this._connecting) {
this._transmit(this._synack);
return;
}
if (packet.id === PACKET_RESET) {
this.push(null);
this.end();
this._closing();
return;
}
if (this._connecting) {
if (packet.id !== PACKET_STATE) return this._incoming.put(packet.seq, packet);
this._ack = uint16(packet.seq-1);
this._recvAck(packet.ack);
this._connecting = false;
this.emit('connect');
packet = this._incoming.del(packet.seq);
if (!packet) return;
}
if (uint16(packet.seq - this._ack) >= BUFFER_SIZE) return this._sendAck(); // old packet
this._recvAck(packet.ack); // TODO: other calcs as well
if (packet.id === PACKET_STATE) return;
this._incoming.put(packet.seq, packet);
while (packet = this._incoming.del(this._ack+1)) {
this._ack = uint16(this._ack+1);
if (packet.id === PACKET_DATA) this.push(packet.data);
if (packet.id === PACKET_FIN) this.push(null);
}
this._sendAck();
};
Connection.prototype._sendAck = function() {
this._transmit(createPacket(this, PACKET_STATE, null)); // TODO: make this delayed
};
Connection.prototype._sendOutgoing = function(packet) {
this._outgoing.put(packet.seq, packet);
this._seq = uint16(this._seq + 1);
this._inflightPackets++;
this._transmit(packet);
};
Connection.prototype._transmit = function(packet) {
packet.sent = packet.sent === 0 ? packet.timestamp : timestamp();
var message = packetToBuffer(packet);
this._alive = true;
this.socket.send(message, 0, message.length, this.port, this.host);
};
var Server = function() {
EventEmitter.call(this);
this._socket = null;
this._connections = {};
};
util.inherits(Server, EventEmitter);
Server.prototype.address = function() {
return this._socket.address();
};
Server.prototype.listenSocket = function(socket, onlistening) {
this._socket = socket;
var connections = this._connections;
var self = this;
socket.on('message', function(message, rinfo) {
if (message.length < MIN_PACKET_SIZE) return;
var packet = bufferToPacket(message);
var id = rinfo.address+':'+(packet.id === PACKET_SYN ? uint16(packet.connection+1) : packet.connection);
if (connections[id]) return connections[id]._recvIncoming(packet);
if (packet.id !== PACKET_SYN || self._closed) return;
connections[id] = new Connection(rinfo.port, rinfo.address, socket, packet);
connections[id].on('close', function() {
delete connections[id];
});
self.emit('connection', connections[id]);
});
socket.once('listening', function() {
self.emit('listening');
});
if (onlistening) self.once('listening', onlistening);
}
Server.prototype.listen = function(port, onlistening) {
if (typeof port === 'object' && typeof port.on === 'function') return this.listenSocket(port, onlistening);
var socket = dgram.createSocket('udp4');
this.listenSocket(socket, onlistening);
socket.bind(port);
};
Server.prototype.close = function(cb) {
var self = this;
var openConnections = 0;
this._closed = true;
function onClose() {
if (--openConnections === 0) {
if (self._socket) self._socket.close();
if (cb) cb();
}
}
for (var id in this._connections) {
if (this._connections[id]._closed) continue;
openConnections++;
this._connections[id].once('close', onClose);
this._connections[id].end();
}
};
exports.createServer = function(onconnection) {
var server = new Server();
if (onconnection) server.on('connection', onconnection);
return server;
};
exports.connect = function(port, host) {
var socket = dgram.createSocket('udp4');
var connection = new Connection(port, host || '127.0.0.1', socket, null);
socket.on('message', function(message) {
if (message.length < MIN_PACKET_SIZE) return;
var packet = bufferToPacket(message);
if (packet.id === PACKET_SYN) return;
if (packet.connection !== connection._recvId) return;
connection._recvIncoming(packet);
});
return connection;
};