work.suroh.tk/node_modules/engine.io/lib/transports/polling.js

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2019-12-02 12:22:45 +00:00
/**
* Module requirements.
*/
var Transport = require('../transport');
var parser = require('engine.io-parser');
var zlib = require('zlib');
var accepts = require('accepts');
var util = require('util');
var debug = require('debug')('engine:polling');
var compressionMethods = {
gzip: zlib.createGzip,
deflate: zlib.createDeflate
};
/**
* Exports the constructor.
*/
module.exports = Polling;
/**
* HTTP polling constructor.
*
* @api public.
*/
function Polling (req) {
Transport.call(this, req);
this.closeTimeout = 30 * 1000;
this.maxHttpBufferSize = null;
this.httpCompression = null;
}
/**
* Inherits from Transport.
*
* @api public.
*/
util.inherits(Polling, Transport);
/**
* Transport name
*
* @api public
*/
Polling.prototype.name = 'polling';
/**
* Overrides onRequest.
*
* @param {http.IncomingMessage}
* @api private
*/
Polling.prototype.onRequest = function (req) {
var res = req.res;
if ('GET' === req.method) {
this.onPollRequest(req, res);
} else if ('POST' === req.method) {
this.onDataRequest(req, res);
} else {
res.writeHead(500);
res.end();
}
};
/**
* The client sends a request awaiting for us to send data.
*
* @api private
*/
Polling.prototype.onPollRequest = function (req, res) {
if (this.req) {
debug('request overlap');
// assert: this.res, '.req and .res should be (un)set together'
this.onError('overlap from client');
res.writeHead(500);
res.end();
return;
}
debug('setting request');
this.req = req;
this.res = res;
var self = this;
function onClose () {
self.onError('poll connection closed prematurely');
}
function cleanup () {
req.removeListener('close', onClose);
self.req = self.res = null;
}
req.cleanup = cleanup;
req.on('close', onClose);
this.writable = true;
this.emit('drain');
// if we're still writable but had a pending close, trigger an empty send
if (this.writable && this.shouldClose) {
debug('triggering empty send to append close packet');
this.send([{ type: 'noop' }]);
}
};
/**
* The client sends a request with data.
*
* @api private
*/
Polling.prototype.onDataRequest = function (req, res) {
if (this.dataReq) {
// assert: this.dataRes, '.dataReq and .dataRes should be (un)set together'
this.onError('data request overlap from client');
res.writeHead(500);
res.end();
return;
}
var isBinary = 'application/octet-stream' === req.headers['content-type'];
this.dataReq = req;
this.dataRes = res;
var chunks = isBinary ? Buffer.concat([]) : '';
var self = this;
function cleanup () {
req.removeListener('data', onData);
req.removeListener('end', onEnd);
req.removeListener('close', onClose);
self.dataReq = self.dataRes = chunks = null;
}
function onClose () {
cleanup();
self.onError('data request connection closed prematurely');
}
function onData (data) {
var contentLength;
if (isBinary) {
chunks = Buffer.concat([chunks, data]);
contentLength = chunks.length;
} else {
chunks += data;
contentLength = Buffer.byteLength(chunks);
}
if (contentLength > self.maxHttpBufferSize) {
chunks = isBinary ? Buffer.concat([]) : '';
req.connection.destroy();
}
}
function onEnd () {
self.onData(chunks);
var headers = {
// text/html is required instead of text/plain to avoid an
// unwanted download dialog on certain user-agents (GH-43)
'Content-Type': 'text/html',
'Content-Length': 2
};
res.writeHead(200, self.headers(req, headers));
res.end('ok');
cleanup();
}
req.on('close', onClose);
if (!isBinary) req.setEncoding('utf8');
req.on('data', onData);
req.on('end', onEnd);
};
/**
* Processes the incoming data payload.
*
* @param {String} encoded payload
* @api private
*/
Polling.prototype.onData = function (data) {
debug('received "%s"', data);
var self = this;
var callback = function (packet) {
if ('close' === packet.type) {
debug('got xhr close packet');
self.onClose();
return false;
}
self.onPacket(packet);
};
parser.decodePayload(data, callback);
};
/**
* Overrides onClose.
*
* @api private
*/
Polling.prototype.onClose = function () {
if (this.writable) {
// close pending poll request
this.send([{ type: 'noop' }]);
}
Transport.prototype.onClose.call(this);
};
/**
* Writes a packet payload.
*
* @param {Object} packet
* @api private
*/
Polling.prototype.send = function (packets) {
this.writable = false;
if (this.shouldClose) {
debug('appending close packet to payload');
packets.push({ type: 'close' });
this.shouldClose();
this.shouldClose = null;
}
var self = this;
parser.encodePayload(packets, this.supportsBinary, function (data) {
var compress = packets.some(function (packet) {
return packet.options && packet.options.compress;
});
self.write(data, { compress: compress });
});
};
/**
* Writes data as response to poll request.
*
* @param {String} data
* @param {Object} options
* @api private
*/
Polling.prototype.write = function (data, options) {
debug('writing "%s"', data);
var self = this;
this.doWrite(data, options, function () {
self.req.cleanup();
});
};
/**
* Performs the write.
*
* @api private
*/
Polling.prototype.doWrite = function (data, options, callback) {
var self = this;
// explicit UTF-8 is required for pages not served under utf
var isString = typeof data === 'string';
var contentType = isString
? 'text/plain; charset=UTF-8'
: 'application/octet-stream';
var headers = {
'Content-Type': contentType
};
if (!this.httpCompression || !options.compress) {
respond(data);
return;
}
var len = isString ? Buffer.byteLength(data) : data.length;
if (len < this.httpCompression.threshold) {
respond(data);
return;
}
var encoding = accepts(this.req).encodings(['gzip', 'deflate']);
if (!encoding) {
respond(data);
return;
}
this.compress(data, encoding, function (err, data) {
if (err) {
self.res.writeHead(500);
self.res.end();
callback(err);
return;
}
headers['Content-Encoding'] = encoding;
respond(data);
});
function respond (data) {
headers['Content-Length'] = 'string' === typeof data ? Buffer.byteLength(data) : data.length;
self.res.writeHead(200, self.headers(self.req, headers));
self.res.end(data);
callback();
}
};
/**
* Compresses data.
*
* @api private
*/
Polling.prototype.compress = function (data, encoding, callback) {
debug('compressing');
var buffers = [];
var nread = 0;
compressionMethods[encoding](this.httpCompression)
.on('error', callback)
.on('data', function (chunk) {
buffers.push(chunk);
nread += chunk.length;
})
.on('end', function () {
callback(null, Buffer.concat(buffers, nread));
})
.end(data);
};
/**
* Closes the transport.
*
* @api private
*/
Polling.prototype.doClose = function (fn) {
debug('closing');
var self = this;
var closeTimeoutTimer;
if (this.dataReq) {
debug('aborting ongoing data request');
this.dataReq.destroy();
}
if (this.writable) {
debug('transport writable - closing right away');
this.send([{ type: 'close' }]);
onClose();
} else if (this.discarded) {
debug('transport discarded - closing right away');
onClose();
} else {
debug('transport not writable - buffering orderly close');
this.shouldClose = onClose;
closeTimeoutTimer = setTimeout(onClose, this.closeTimeout);
}
function onClose () {
clearTimeout(closeTimeoutTimer);
fn();
self.onClose();
}
};
/**
* Returns headers for a response.
*
* @param {http.IncomingMessage} request
* @param {Object} extra headers
* @api private
*/
Polling.prototype.headers = function (req, headers) {
headers = headers || {};
// prevent XSS warnings on IE
// https://github.com/LearnBoost/socket.io/pull/1333
var ua = req.headers['user-agent'];
if (ua && (~ua.indexOf(';MSIE') || ~ua.indexOf('Trident/'))) {
headers['X-XSS-Protection'] = '0';
}
this.emit('headers', headers);
return headers;
};