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/**
* Module dependencies.
*/
var Transport = require('../transport');
var parseqs = require('parseqs');
var parser = require('engine.io-parser');
var inherit = require('component-inherit');
var yeast = require('yeast');
var debug = require('debug')('engine.io-client:polling');
/**
* Module exports.
*/
module.exports = Polling;
/**
* Is XHR2 supported?
*/
var hasXHR2 = (function () {
var XMLHttpRequest = require('xmlhttprequest-ssl');
var xhr = new XMLHttpRequest({ xdomain: false });
return null != xhr.responseType;
})();
/**
* Polling interface.
*
* @param {Object} opts
* @api private
*/
function Polling (opts) {
var forceBase64 = (opts && opts.forceBase64);
if (!hasXHR2 || forceBase64) {
this.supportsBinary = false;
}
Transport.call(this, opts);
}
/**
* Inherits from Transport.
*/
inherit(Polling, Transport);
/**
* Transport name.
*/
Polling.prototype.name = 'polling';
/**
* Opens the socket (triggers polling). We write a PING message to determine
* when the transport is open.
*
* @api private
*/
Polling.prototype.doOpen = function () {
this.poll();
};
/**
* Pauses polling.
*
* @param {Function} callback upon buffers are flushed and transport is paused
* @api private
*/
Polling.prototype.pause = function (onPause) {
var self = this;
this.readyState = 'pausing';
function pause () {
debug('paused');
self.readyState = 'paused';
onPause();
}
if (this.polling || !this.writable) {
var total = 0;
if (this.polling) {
debug('we are currently polling - waiting to pause');
total++;
this.once('pollComplete', function () {
debug('pre-pause polling complete');
--total || pause();
});
}
if (!this.writable) {
debug('we are currently writing - waiting to pause');
total++;
this.once('drain', function () {
debug('pre-pause writing complete');
--total || pause();
});
}
} else {
pause();
}
};
/**
* Starts polling cycle.
*
* @api public
*/
Polling.prototype.poll = function () {
debug('polling');
this.polling = true;
this.doPoll();
this.emit('poll');
};
/**
* Overloads onData to detect payloads.
*
* @api private
*/
Polling.prototype.onData = function (data) {
var self = this;
debug('polling got data %s', data);
var callback = function (packet, index, total) {
// if its the first message we consider the transport open
if ('opening' === self.readyState) {
self.onOpen();
}
// if its a close packet, we close the ongoing requests
if ('close' === packet.type) {
self.onClose();
return false;
}
// otherwise bypass onData and handle the message
self.onPacket(packet);
};
// decode payload
parser.decodePayload(data, this.socket.binaryType, callback);
// if an event did not trigger closing
if ('closed' !== this.readyState) {
// if we got data we're not polling
this.polling = false;
this.emit('pollComplete');
if ('open' === this.readyState) {
this.poll();
} else {
debug('ignoring poll - transport state "%s"', this.readyState);
}
}
};
/**
* For polling, send a close packet.
*
* @api private
*/
Polling.prototype.doClose = function () {
var self = this;
function close () {
debug('writing close packet');
self.write([{ type: 'close' }]);
}
if ('open' === this.readyState) {
debug('transport open - closing');
close();
} else {
// in case we're trying to close while
// handshaking is in progress (GH-164)
debug('transport not open - deferring close');
this.once('open', close);
}
};
/**
* Writes a packets payload.
*
* @param {Array} data packets
* @param {Function} drain callback
* @api private
*/
Polling.prototype.write = function (packets) {
var self = this;
this.writable = false;
var callbackfn = function () {
self.writable = true;
self.emit('drain');
};
parser.encodePayload(packets, this.supportsBinary, function (data) {
self.doWrite(data, callbackfn);
});
};
/**
* Generates uri for connection.
*
* @api private
*/
Polling.prototype.uri = function () {
var query = this.query || {};
var schema = this.secure ? 'https' : 'http';
var port = '';
// cache busting is forced
if (false !== this.timestampRequests) {
query[this.timestampParam] = yeast();
}
if (!this.supportsBinary && !query.sid) {
query.b64 = 1;
}
query = parseqs.encode(query);
// avoid port if default for schema
if (this.port && (('https' === schema && Number(this.port) !== 443) ||
('http' === schema && Number(this.port) !== 80))) {
port = ':' + this.port;
}
// prepend ? to query
if (query.length) {
query = '?' + query;
}
var ipv6 = this.hostname.indexOf(':') !== -1;
return schema + '://' + (ipv6 ? '[' + this.hostname + ']' : this.hostname) + port + this.path + query;
};
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