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// Copyright 2006 The Closure Library Authors. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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//      http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS-IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/**
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 * @fileoverview Definition of the BrowserChannel class.  A BrowserChannel
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 * simulates a bidirectional socket over HTTP. It is the basis of the
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 * Gmail Chat IM connections to the server.
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 *
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 * Typical usage will look like
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 *  var handler = [handler object];
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 *  var channel = new BrowserChannel(clientVersion);
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 *  channel.setHandler(handler);
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 *  channel.connect('channel/test', 'channel/bind');
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 *
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 * See goog.net.BrowserChannel.Handler for the handler interface.
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 *
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 */
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goog.provide('goog.net.BrowserChannel');
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goog.provide('goog.net.BrowserChannel.Error');
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goog.provide('goog.net.BrowserChannel.Event');
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goog.provide('goog.net.BrowserChannel.Handler');
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goog.provide('goog.net.BrowserChannel.LogSaver');
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goog.provide('goog.net.BrowserChannel.QueuedMap');
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goog.provide('goog.net.BrowserChannel.ServerReachability');
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goog.provide('goog.net.BrowserChannel.ServerReachabilityEvent');
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goog.provide('goog.net.BrowserChannel.Stat');
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goog.provide('goog.net.BrowserChannel.StatEvent');
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goog.provide('goog.net.BrowserChannel.State');
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goog.provide('goog.net.BrowserChannel.TimingEvent');
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goog.require('goog.Uri');
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goog.require('goog.array');
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goog.require('goog.asserts');
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goog.require('goog.debug.TextFormatter');
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goog.require('goog.events.Event');
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goog.require('goog.events.EventTarget');
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goog.require('goog.json');
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goog.require('goog.json.NativeJsonProcessor');
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goog.require('goog.log');
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goog.require('goog.net.BrowserTestChannel');
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goog.require('goog.net.ChannelDebug');
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goog.require('goog.net.ChannelRequest');
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goog.require('goog.net.XhrIo');
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goog.require('goog.net.tmpnetwork');
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goog.require('goog.object');
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goog.require('goog.string');
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goog.require('goog.structs');
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goog.require('goog.structs.CircularBuffer');
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/**
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 * Encapsulates the logic for a single BrowserChannel.
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 *
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 * @param {string=} opt_clientVersion An application-specific version number
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 *        that is sent to the server when connected.
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 * @param {Array<string>=} opt_firstTestResults Previously determined results
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 *        of the first browser channel test.
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 * @param {boolean=} opt_secondTestResults Previously determined results
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 *        of the second browser channel test.
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 * @param {boolean=} opt_asyncTest Whether to perform the test requests
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 *        asynchronously. While the test is performed, we'll assume the worst
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 *        (connection is buffered), in order to avoid delaying the connection
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 *        until the test is performed.
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 * @constructor
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 */
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goog.net.BrowserChannel = function(
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    opt_clientVersion, opt_firstTestResults, opt_secondTestResults,
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    opt_asyncTest) {
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  /**
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   * The application specific version that is passed to the server.
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   * @type {?string}
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   * @private
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   */
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  this.clientVersion_ = opt_clientVersion || null;
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  /**
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   * The current state of the BrowserChannel. It should be one of the
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   * goog.net.BrowserChannel.State constants.
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   * @type {!goog.net.BrowserChannel.State}
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   * @private
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   */
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  this.state_ = goog.net.BrowserChannel.State.INIT;
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  /**
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   * An array of queued maps that need to be sent to the server.
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   * @type {Array<goog.net.BrowserChannel.QueuedMap>}
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   * @private
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   */
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  this.outgoingMaps_ = [];
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  /**
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   * An array of dequeued maps that we have either received a non-successful
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   * response for, or no response at all, and which therefore may or may not
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   * have been received by the server.
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   * @type {Array<goog.net.BrowserChannel.QueuedMap>}
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   * @private
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   */
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  this.pendingMaps_ = [];
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  /**
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   * The channel debug used for browserchannel logging
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   * @type {!goog.net.ChannelDebug}
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   * @private
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   */
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  this.channelDebug_ = new goog.net.ChannelDebug();
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  /**
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   * Parser for a response payload. The parser should return an array.
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   * @type {!goog.string.Parser}
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   * @private
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   */
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  this.parser_ = new goog.json.NativeJsonProcessor();
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  /**
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   * An array of results for the first browser channel test call.
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   * @type {Array<string>}
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   * @private
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   */
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  this.firstTestResults_ = opt_firstTestResults || null;
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  /**
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   * The results of the second browser channel test. True implies the
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   * connection is buffered, False means unbuffered, null means that
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   * the results are not available.
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   * @private
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   */
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  this.secondTestResults_ = goog.isDefAndNotNull(opt_secondTestResults) ?
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      opt_secondTestResults :
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      null;
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  /**
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   * Whether to perform the test requests asynchronously. While the test is
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   * performed, we'll assume the worst (connection is buffered), in order to
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   * avoid delaying the connection until the test is performed.
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   * @private {boolean}
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   */
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  this.asyncTest_ = opt_asyncTest || false;
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};
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/**
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 * Simple container class for a (mapId, map) pair.
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 * @param {number} mapId The id for this map.
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 * @param {Object|goog.structs.Map} map The map itself.
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 * @param {Object=} opt_context The context associated with the map.
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 * @constructor
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 * @final
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 */
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goog.net.BrowserChannel.QueuedMap = function(mapId, map, opt_context) {
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  /**
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   * The id for this map.
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   * @type {number}
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   */
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  this.mapId = mapId;
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  /**
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   * The map itself.
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   * @type {Object}
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   */
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  this.map = map;
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  /**
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   * The context for the map.
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   * @type {Object}
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   */
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  this.context = opt_context || null;
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};
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/**
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 * Extra HTTP headers to add to all the requests sent to the server.
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 * @type {Object}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.extraHeaders_ = null;
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/**
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 * Extra parameters to add to all the requests sent to the server.
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 * @type {Object}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.extraParams_ = null;
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/**
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 * The current ChannelRequest object for the forwardchannel.
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 * @type {goog.net.ChannelRequest?}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.forwardChannelRequest_ = null;
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/**
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 * The ChannelRequest object for the backchannel.
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 * @type {goog.net.ChannelRequest?}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.backChannelRequest_ = null;
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/**
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 * The relative path (in the context of the the page hosting the browser
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 * channel) for making requests to the server.
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 * @type {?string}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.path_ = null;
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/**
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 * The absolute URI for the forwardchannel request.
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 * @type {goog.Uri}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.forwardChannelUri_ = null;
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/**
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 * The absolute URI for the backchannel request.
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 * @type {goog.Uri}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.backChannelUri_ = null;
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/**
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 * A subdomain prefix for using a subdomain in IE for the backchannel
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 * requests.
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 * @type {?string}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.hostPrefix_ = null;
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/**
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 * Whether we allow the use of a subdomain in IE for the backchannel requests.
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 * @private
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 */
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goog.net.BrowserChannel.prototype.allowHostPrefix_ = true;
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/**
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 * The next id to use for the RID (request identifier) parameter. This
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 * identifier uniquely identifies the forward channel request.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.nextRid_ = 0;
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/**
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 * The id to use for the next outgoing map. This identifier uniquely
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 * identifies a sent map.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.nextMapId_ = 0;
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/**
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 * Whether to fail forward-channel requests after one try, or after a few tries.
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 * @type {boolean}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.failFast_ = false;
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/**
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 * The handler that receive callbacks for state changes and data.
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 * @type {goog.net.BrowserChannel.Handler}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.handler_ = null;
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/**
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 * Timer identifier for asynchronously making a forward channel request.
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 * @type {?number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.forwardChannelTimerId_ = null;
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/**
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 * Timer identifier for asynchronously making a back channel request.
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 * @type {?number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.backChannelTimerId_ = null;
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/**
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 * Timer identifier for the timer that waits for us to retry the backchannel in
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 * the case where it is dead and no longer receiving data.
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 * @type {?number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.deadBackChannelTimerId_ = null;
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/**
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 * The BrowserTestChannel object which encapsulates the logic for determining
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 * interesting network conditions about the client.
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 * @type {goog.net.BrowserTestChannel?}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.connectionTest_ = null;
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/**
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 * Whether the client's network conditions can support chunked responses.
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 * @type {?boolean}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.useChunked_ = null;
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/**
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 * Whether chunked mode is allowed. In certain debugging situations, it's
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 * useful to disable this.
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 * @private
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 */
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goog.net.BrowserChannel.prototype.allowChunkedMode_ = true;
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/**
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 * The array identifier of the last array received from the server for the
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 * backchannel request.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.lastArrayId_ = -1;
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/**
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 * The array identifier of the last array sent by the server that we know about.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.lastPostResponseArrayId_ = -1;
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/**
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 * The last status code received.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.lastStatusCode_ = -1;
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/**
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 * Number of times we have retried the current forward channel request.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.forwardChannelRetryCount_ = 0;
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374

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/**
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 * Number of times it a row that we have retried the current back channel
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 * request and received no data.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.backChannelRetryCount_ = 0;
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383

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/**
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 * The attempt id for the current back channel request. Starts at 1 and
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 * increments for each reconnect. The server uses this to log if our connection
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 * is flaky or not.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.backChannelAttemptId_;
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/**
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 * The base part of the time before firing next retry request. Default is 5
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 * seconds. Note that a random delay is added (see {@link retryDelaySeedMs_})
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 * for all retries, and linear backoff is applied to the sum for subsequent
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 * retries.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.baseRetryDelayMs_ = 5 * 1000;
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/**
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 * A random time between 0 and this number of MS is added to the
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 * {@link baseRetryDelayMs_}. Default is 10 seconds.
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 * @type {number}
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 * @private
410
 */
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goog.net.BrowserChannel.prototype.retryDelaySeedMs_ = 10 * 1000;
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413

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/**
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 * Maximum number of attempts to connect to the server for forward channel
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 * requests. Defaults to 2.
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 * @type {number}
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 * @private
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 */
420
goog.net.BrowserChannel.prototype.forwardChannelMaxRetries_ = 2;
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422

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/**
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 * The timeout in milliseconds for a forward channel request. Defaults to 20
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 * seconds. Note that part of this timeout can be randomized.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.forwardChannelRequestTimeoutMs_ = 20 * 1000;
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/**
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 * A throttle time in ms for readystatechange events for the backchannel.
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 * Useful for throttling when ready state is INTERACTIVE (partial data).
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 *
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 * This throttle is useful if the server sends large data chunks down the
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 * backchannel.  It prevents examining XHR partial data on every
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 * readystate change event.  This is useful because large chunks can
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 * trigger hundreds of readystatechange events, each of which takes ~5ms
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 * or so to handle, in turn making the UI unresponsive for a significant period.
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 *
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 * If set to zero no throttle is used.
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 * @type {number}
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 * @private
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 */
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goog.net.BrowserChannel.prototype.readyStateChangeThrottleMs_ = 0;
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448

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/**
450
 * Whether cross origin requests are supported for the browser channel.
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 *
452
 * See {@link goog.net.XhrIo#setWithCredentials}.
453
 * @type {boolean}
454
 * @private
455
 */
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goog.net.BrowserChannel.prototype.supportsCrossDomainXhrs_ = false;
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458

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/**
460
 * The latest protocol version that this class supports. We request this version
461
 * from the server when opening the connection. Should match
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 * com.google.net.browserchannel.BrowserChannel.LATEST_CHANNEL_VERSION.
463
 * @type {number}
464
 */
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goog.net.BrowserChannel.LATEST_CHANNEL_VERSION = 8;
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467

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/**
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 * The channel version that we negotiated with the server for this session.
470
 * Starts out as the version we request, and then is changed to the negotiated
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 * version after the initial open.
472
 * @type {number}
473
 * @private
474
 */
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goog.net.BrowserChannel.prototype.channelVersion_ =
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    goog.net.BrowserChannel.LATEST_CHANNEL_VERSION;
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478

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/**
480
 * Enum type for the browser channel state machine.
481
 * @enum {number}
482
 */
483
goog.net.BrowserChannel.State = {
484
  /** The channel is closed. */
485
  CLOSED: 0,
486

487
  /** The channel has been initialized but hasn't yet initiated a connection. */
488
  INIT: 1,
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490
  /** The channel is in the process of opening a connection to the server. */
491
  OPENING: 2,
492

493
  /** The channel is open. */
494
  OPENED: 3
495
};
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497

498
/**
499
 * The timeout in milliseconds for a forward channel request.
500
 * @type {number}
501
 */
502
goog.net.BrowserChannel.FORWARD_CHANNEL_RETRY_TIMEOUT = 20 * 1000;
503

504

505
/**
506
 * Maximum number of attempts to connect to the server for back channel
507
 * requests.
508
 * @type {number}
509
 */
510
goog.net.BrowserChannel.BACK_CHANNEL_MAX_RETRIES = 3;
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512

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/**
514
 * A number in MS of how long we guess the maxmium amount of time a round trip
515
 * to the server should take. In the future this could be substituted with a
516
 * real measurement of the RTT.
517
 * @type {number}
518
 */
519
goog.net.BrowserChannel.RTT_ESTIMATE = 3 * 1000;
520

521

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/**
523
 * When retrying for an inactive channel, we will multiply the total delay by
524
 * this number.
525
 * @type {number}
526
 */
527
goog.net.BrowserChannel.INACTIVE_CHANNEL_RETRY_FACTOR = 2;
528

529

530
/**
531
 * Enum type for identifying a BrowserChannel error.
532
 * @enum {number}
533
 */
534
goog.net.BrowserChannel.Error = {
535
  /** Value that indicates no error has occurred. */
536
  OK: 0,
537

538
  /** An error due to a request failing. */
539
  REQUEST_FAILED: 2,
540

541
  /** An error due to the user being logged out. */
542
  LOGGED_OUT: 4,
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544
  /** An error due to server response which contains no data. */
545
  NO_DATA: 5,
546

547
  /** An error due to a server response indicating an unknown session id */
548
  UNKNOWN_SESSION_ID: 6,
549

550
  /** An error due to a server response requesting to stop the channel. */
551
  STOP: 7,
552

553
  /** A general network error. */
554
  NETWORK: 8,
555

556
  /** An error due to the channel being blocked by a network administrator. */
557
  BLOCKED: 9,
558

559
  /** An error due to bad data being returned from the server. */
560
  BAD_DATA: 10,
561

562
  /** An error due to a response that doesn't start with the magic cookie. */
563
  BAD_RESPONSE: 11,
564

565
  /** ActiveX is blocked by the machine's admin settings. */
566
  ACTIVE_X_BLOCKED: 12
567
};
568

569

570
/**
571
 * Internal enum type for the two browser channel channel types.
572
 * @enum {number}
573
 * @private
574
 */
575
goog.net.BrowserChannel.ChannelType_ = {
576
  FORWARD_CHANNEL: 1,
577

578
  BACK_CHANNEL: 2
579
};
580

581

582
/**
583
 * The maximum number of maps that can be sent in one POST. Should match
584
 * com.google.net.browserchannel.BrowserChannel.MAX_MAPS_PER_REQUEST.
585
 * @type {number}
586
 * @private
587
 */
588
goog.net.BrowserChannel.MAX_MAPS_PER_REQUEST_ = 1000;
589

590

591
/**
592
 * Singleton event target for firing stat events
593
 * @type {goog.events.EventTarget}
594
 * @private
595
 */
596
goog.net.BrowserChannel.statEventTarget_ = new goog.events.EventTarget();
597

598

599
/**
600
 * Events fired by BrowserChannel and associated objects
601
 * @const
602
 */
603
goog.net.BrowserChannel.Event = {};
604

605

606
/**
607
 * Stat Event that fires when things of interest happen that may be useful for
608
 * applications to know about for stats or debugging purposes. This event fires
609
 * on the EventTarget returned by getStatEventTarget.
610
 */
611
goog.net.BrowserChannel.Event.STAT_EVENT = 'statevent';
612

613

614

615
/**
616
 * Event class for goog.net.BrowserChannel.Event.STAT_EVENT
617
 *
618
 * @param {goog.events.EventTarget} eventTarget The stat event target for
619
       the browser channel.
620
 * @param {goog.net.BrowserChannel.Stat} stat The stat.
621
 * @constructor
622
 * @extends {goog.events.Event}
623
 * @final
624
 */
625
goog.net.BrowserChannel.StatEvent = function(eventTarget, stat) {
626
  goog.events.Event.call(
627
      this, goog.net.BrowserChannel.Event.STAT_EVENT, eventTarget);
628

629
  /**
630
   * The stat
631
   * @type {goog.net.BrowserChannel.Stat}
632
   */
633
  this.stat = stat;
634

635
};
636
goog.inherits(goog.net.BrowserChannel.StatEvent, goog.events.Event);
637

638

639
/**
640
 * An event that fires when POST requests complete successfully, indicating
641
 * the size of the POST and the round trip time.
642
 * This event fires on the EventTarget returned by getStatEventTarget.
643
 */
644
goog.net.BrowserChannel.Event.TIMING_EVENT = 'timingevent';
645

646

647

648
/**
649
 * Event class for goog.net.BrowserChannel.Event.TIMING_EVENT
650
 *
651
 * @param {goog.events.EventTarget} target The stat event target for
652
       the browser channel.
653
 * @param {number} size The number of characters in the POST data.
654
 * @param {number} rtt The total round trip time from POST to response in MS.
655
 * @param {number} retries The number of times the POST had to be retried.
656
 * @constructor
657
 * @extends {goog.events.Event}
658
 * @final
659
 */
660
goog.net.BrowserChannel.TimingEvent = function(target, size, rtt, retries) {
661
  goog.events.Event.call(
662
      this, goog.net.BrowserChannel.Event.TIMING_EVENT, target);
663

664
  /**
665
   * @type {number}
666
   */
667
  this.size = size;
668

669
  /**
670
   * @type {number}
671
   */
672
  this.rtt = rtt;
673

674
  /**
675
   * @type {number}
676
   */
677
  this.retries = retries;
678

679
};
680
goog.inherits(goog.net.BrowserChannel.TimingEvent, goog.events.Event);
681

682

683
/**
684
 * The type of event that occurs every time some information about how reachable
685
 * the server is is discovered.
686
 */
687
goog.net.BrowserChannel.Event.SERVER_REACHABILITY_EVENT = 'serverreachability';
688

689

690
/**
691
 * Types of events which reveal information about the reachability of the
692
 * server.
693
 * @enum {number}
694
 */
695
goog.net.BrowserChannel.ServerReachability = {
696
  REQUEST_MADE: 1,
697
  REQUEST_SUCCEEDED: 2,
698
  REQUEST_FAILED: 3,
699
  BACK_CHANNEL_ACTIVITY: 4
700
};
701

702

703

704
/**
705
 * Event class for goog.net.BrowserChannel.Event.SERVER_REACHABILITY_EVENT.
706
 *
707
 * @param {goog.events.EventTarget} target The stat event target for
708
       the browser channel.
709
 * @param {goog.net.BrowserChannel.ServerReachability} reachabilityType The
710
 *     reachability event type.
711
 * @constructor
712
 * @extends {goog.events.Event}
713
 * @final
714
 */
715
goog.net.BrowserChannel.ServerReachabilityEvent = function(
716
    target, reachabilityType) {
717
  goog.events.Event.call(
718
      this, goog.net.BrowserChannel.Event.SERVER_REACHABILITY_EVENT, target);
719

720
  /**
721
   * @type {goog.net.BrowserChannel.ServerReachability}
722
   */
723
  this.reachabilityType = reachabilityType;
724
};
725
goog.inherits(
726
    goog.net.BrowserChannel.ServerReachabilityEvent, goog.events.Event);
727

728

729
/**
730
 * Enum that identifies events for statistics that are interesting to track.
731
 * TODO(user) - Change name not to use Event or use EventTarget
732
 * @enum {number}
733
 */
734
goog.net.BrowserChannel.Stat = {
735
  /** Event indicating a new connection attempt. */
736
  CONNECT_ATTEMPT: 0,
737

738
  /** Event indicating a connection error due to a general network problem. */
739
  ERROR_NETWORK: 1,
740

741
  /**
742
   * Event indicating a connection error that isn't due to a general network
743
   * problem.
744
   */
745
  ERROR_OTHER: 2,
746

747
  /** Event indicating the start of test stage one. */
748
  TEST_STAGE_ONE_START: 3,
749

750

751
  /** Event indicating the channel is blocked by a network administrator. */
752
  CHANNEL_BLOCKED: 4,
753

754
  /** Event indicating the start of test stage two. */
755
  TEST_STAGE_TWO_START: 5,
756

757
  /** Event indicating the first piece of test data was received. */
758
  TEST_STAGE_TWO_DATA_ONE: 6,
759

760
  /**
761
   * Event indicating that the second piece of test data was received and it was
762
   * received separately from the first.
763
   */
764
  TEST_STAGE_TWO_DATA_TWO: 7,
765

766
  /** Event indicating both pieces of test data were received simultaneously. */
767
  TEST_STAGE_TWO_DATA_BOTH: 8,
768

769
  /** Event indicating stage one of the test request failed. */
770
  TEST_STAGE_ONE_FAILED: 9,
771

772
  /** Event indicating stage two of the test request failed. */
773
  TEST_STAGE_TWO_FAILED: 10,
774

775
  /**
776
   * Event indicating that a buffering proxy is likely between the client and
777
   * the server.
778
   */
779
  PROXY: 11,
780

781
  /**
782
   * Event indicating that no buffering proxy is likely between the client and
783
   * the server.
784
   */
785
  NOPROXY: 12,
786

787
  /** Event indicating an unknown SID error. */
788
  REQUEST_UNKNOWN_SESSION_ID: 13,
789

790
  /** Event indicating a bad status code was received. */
791
  REQUEST_BAD_STATUS: 14,
792

793
  /** Event indicating incomplete data was received */
794
  REQUEST_INCOMPLETE_DATA: 15,
795

796
  /** Event indicating bad data was received */
797
  REQUEST_BAD_DATA: 16,
798

799
  /** Event indicating no data was received when data was expected. */
800
  REQUEST_NO_DATA: 17,
801

802
  /** Event indicating a request timeout. */
803
  REQUEST_TIMEOUT: 18,
804

805
  /**
806
   * Event indicating that the server never received our hanging GET and so it
807
   * is being retried.
808
   */
809
  BACKCHANNEL_MISSING: 19,
810

811
  /**
812
   * Event indicating that we have determined that our hanging GET is not
813
   * receiving data when it should be. Thus it is dead dead and will be retried.
814
   */
815
  BACKCHANNEL_DEAD: 20,
816

817
  /**
818
   * The browser declared itself offline during the lifetime of a request, or
819
   * was offline when a request was initially made.
820
   */
821
  BROWSER_OFFLINE: 21,
822

823
  /** ActiveX is blocked by the machine's admin settings. */
824
  ACTIVE_X_BLOCKED: 22
825
};
826

827

828
/**
829
 * A guess at a cutoff at which to no longer assume the backchannel is dead
830
 * when we are slow to receive data. Number in bytes.
831
 *
832
 * Assumption: The worst bandwidth we work on is 50 kilobits/sec
833
 * 50kbits/sec * (1 byte / 8 bits) * 6 sec dead backchannel timeout
834
 * @type {number}
835
 */
836
goog.net.BrowserChannel.OUTSTANDING_DATA_BACKCHANNEL_RETRY_CUTOFF = 37500;
837

838

839
/**
840
 * Returns the browserchannel logger.
841
 *
842
 * @return {!goog.net.ChannelDebug} The channel debug object.
843
 */
844
goog.net.BrowserChannel.prototype.getChannelDebug = function() {
845
  return this.channelDebug_;
846
};
847

848

849
/**
850
 * Set the browserchannel logger.
851
 * TODO(user): Add interface for channel loggers or remove this function.
852
 *
853
 * @param {goog.net.ChannelDebug} channelDebug The channel debug object.
854
 */
855
goog.net.BrowserChannel.prototype.setChannelDebug = function(channelDebug) {
856
  if (goog.isDefAndNotNull(channelDebug)) {
857
    this.channelDebug_ = channelDebug;
858
  }
859
};
860

861

862
/**
863
 * Allows the application to set an execution hooks for when BrowserChannel
864
 * starts processing requests. This is useful to track timing or logging
865
 * special information. The function takes no parameters and return void.
866
 * @param {Function} startHook  The function for the start hook.
867
 */
868
goog.net.BrowserChannel.setStartThreadExecutionHook = function(startHook) {
869
  goog.net.BrowserChannel.startExecutionHook_ = startHook;
870
};
871

872

873
/**
874
 * Allows the application to set an execution hooks for when BrowserChannel
875
 * stops processing requests. This is useful to track timing or logging
876
 * special information. The function takes no parameters and return void.
877
 * @param {Function} endHook  The function for the end hook.
878
 */
879
goog.net.BrowserChannel.setEndThreadExecutionHook = function(endHook) {
880
  goog.net.BrowserChannel.endExecutionHook_ = endHook;
881
};
882

883

884
/**
885
 * Application provided execution hook for the start hook.
886
 *
887
 * @type {Function}
888
 * @private
889
 */
890
goog.net.BrowserChannel.startExecutionHook_ = function() {};
891

892

893
/**
894
 * Application provided execution hook for the end hook.
895
 *
896
 * @type {Function}
897
 * @private
898
 */
899
goog.net.BrowserChannel.endExecutionHook_ = function() {};
900

901

902
/**
903
 * Instantiates a ChannelRequest with the given parameters. Overidden in tests.
904
 *
905
 * @param {goog.net.BrowserChannel|goog.net.BrowserTestChannel} channel
906
 *     The BrowserChannel that owns this request.
907
 * @param {goog.net.ChannelDebug} channelDebug A ChannelDebug to use for
908
 *     logging.
909
 * @param {string=} opt_sessionId  The session id for the channel.
910
 * @param {string|number=} opt_requestId  The request id for this request.
911
 * @param {number=} opt_retryId  The retry id for this request.
912
 * @return {!goog.net.ChannelRequest} The created channel request.
913
 */
914
goog.net.BrowserChannel.createChannelRequest = function(
915
    channel, channelDebug, opt_sessionId, opt_requestId, opt_retryId) {
916
  return new goog.net.ChannelRequest(
917
      channel, channelDebug, opt_sessionId, opt_requestId, opt_retryId);
918
};
919

920

921
/**
922
 * Starts the channel. This initiates connections to the server.
923
 *
924
 * @param {string} testPath  The path for the test connection.
925
 * @param {string} channelPath  The path for the channel connection.
926
 * @param {Object=} opt_extraParams  Extra parameter keys and values to add to
927
 *     the requests.
928
 * @param {string=} opt_oldSessionId  Session ID from a previous session.
929
 * @param {number=} opt_oldArrayId  The last array ID from a previous session.
930
 */
931
goog.net.BrowserChannel.prototype.connect = function(
932
    testPath, channelPath, opt_extraParams, opt_oldSessionId, opt_oldArrayId) {
933
  this.channelDebug_.debug('connect()');
934

935
  goog.net.BrowserChannel.notifyStatEvent(
936
      goog.net.BrowserChannel.Stat.CONNECT_ATTEMPT);
937

938
  this.path_ = channelPath;
939
  this.extraParams_ = opt_extraParams || {};
940

941
  // Attach parameters about the previous session if reconnecting.
942
  if (opt_oldSessionId && goog.isDef(opt_oldArrayId)) {
943
    this.extraParams_['OSID'] = opt_oldSessionId;
944
    this.extraParams_['OAID'] = opt_oldArrayId;
945
  }
946

947
  if (this.asyncTest_) {
948
    goog.net.BrowserChannel.setTimeout(
949
        goog.bind(this.connectTest_, this, testPath), 100);
950
    this.connectChannel_();
951
  } else {
952
    this.connectTest_(testPath);
953
  }
954
};
955

956

957
/**
958
 * Disconnects and closes the channel.
959
 */
960
goog.net.BrowserChannel.prototype.disconnect = function() {
961
  this.channelDebug_.debug('disconnect()');
962

963
  this.cancelRequests_();
964

965
  if (this.state_ == goog.net.BrowserChannel.State.OPENED) {
966
    var rid = this.nextRid_++;
967
    var uri = this.forwardChannelUri_.clone();
968
    uri.setParameterValue('SID', this.sid_);
969
    uri.setParameterValue('RID', rid);
970
    uri.setParameterValue('TYPE', 'terminate');
971

972
    // Add the reconnect parameters.
973
    this.addAdditionalParams_(uri);
974

975
    var request = goog.net.BrowserChannel.createChannelRequest(
976
        this, this.channelDebug_, this.sid_, rid);
977
    request.sendUsingImgTag(uri);
978
  }
979

980
  this.onClose_();
981
};
982

983

984
/**
985
 * Returns the session id of the channel. Only available after the
986
 * channel has been opened.
987
 * @return {string} Session ID.
988
 */
989
goog.net.BrowserChannel.prototype.getSessionId = function() {
990
  return this.sid_;
991
};
992

993

994
/**
995
 * Starts the test channel to determine network conditions.
996
 *
997
 * @param {string} testPath  The relative PATH for the test connection.
998
 * @private
999
 */
1000
goog.net.BrowserChannel.prototype.connectTest_ = function(testPath) {
1001
  this.channelDebug_.debug('connectTest_()');
1002
  if (!this.okToMakeRequest_()) {
1003
    return;  // channel is cancelled
1004
  }
1005
  this.connectionTest_ =
1006
      new goog.net.BrowserTestChannel(this, this.channelDebug_);
1007
  this.connectionTest_.setExtraHeaders(this.extraHeaders_);
1008
  this.connectionTest_.setParser(this.parser_);
1009
  this.connectionTest_.connect(testPath);
1010
};
1011

1012

1013
/**
1014
 * Starts the regular channel which is run after the test channel is complete.
1015
 * @private
1016
 */
1017
goog.net.BrowserChannel.prototype.connectChannel_ = function() {
1018
  this.channelDebug_.debug('connectChannel_()');
1019
  this.ensureInState_(
1020
      goog.net.BrowserChannel.State.INIT, goog.net.BrowserChannel.State.CLOSED);
1021
  this.forwardChannelUri_ =
1022
      this.getForwardChannelUri(/** @type {string} */ (this.path_));
1023
  this.ensureForwardChannel_();
1024
};
1025

1026

1027
/**
1028
 * Cancels all outstanding requests.
1029
 * @private
1030
 */
1031
goog.net.BrowserChannel.prototype.cancelRequests_ = function() {
1032
  if (this.connectionTest_) {
1033
    this.connectionTest_.abort();
1034
    this.connectionTest_ = null;
1035
  }
1036

1037
  if (this.backChannelRequest_) {
1038
    this.backChannelRequest_.cancel();
1039
    this.backChannelRequest_ = null;
1040
  }
1041

1042
  if (this.backChannelTimerId_) {
1043
    goog.global.clearTimeout(this.backChannelTimerId_);
1044
    this.backChannelTimerId_ = null;
1045
  }
1046

1047
  this.clearDeadBackchannelTimer_();
1048

1049
  if (this.forwardChannelRequest_) {
1050
    this.forwardChannelRequest_.cancel();
1051
    this.forwardChannelRequest_ = null;
1052
  }
1053

1054
  if (this.forwardChannelTimerId_) {
1055
    goog.global.clearTimeout(this.forwardChannelTimerId_);
1056
    this.forwardChannelTimerId_ = null;
1057
  }
1058
};
1059

1060

1061
/**
1062
 * Returns the extra HTTP headers to add to all the requests sent to the server.
1063
 *
1064
 * @return {Object} The HTTP headers, or null.
1065
 */
1066
goog.net.BrowserChannel.prototype.getExtraHeaders = function() {
1067
  return this.extraHeaders_;
1068
};
1069

1070

1071
/**
1072
 * Sets extra HTTP headers to add to all the requests sent to the server.
1073
 *
1074
 * @param {Object} extraHeaders The HTTP headers, or null.
1075
 */
1076
goog.net.BrowserChannel.prototype.setExtraHeaders = function(extraHeaders) {
1077
  this.extraHeaders_ = extraHeaders;
1078
};
1079

1080

1081
/**
1082
 * Sets the throttle for handling onreadystatechange events for the request.
1083
 *
1084
 * @param {number} throttle The throttle in ms.  A value of zero indicates
1085
 *     no throttle.
1086
 */
1087
goog.net.BrowserChannel.prototype.setReadyStateChangeThrottle = function(
1088
    throttle) {
1089
  this.readyStateChangeThrottleMs_ = throttle;
1090
};
1091

1092

1093
/**
1094
 * Sets whether cross origin requests are supported for the browser channel.
1095
 *
1096
 * Setting this allows the creation of requests to secondary domains and
1097
 * sends XHRs with the CORS withCredentials bit set to true.
1098
 *
1099
 * In order for cross-origin requests to work, the server will also need to set
1100
 * CORS response headers as per:
1101
 * https://developer.mozilla.org/en-US/docs/HTTP_access_control
1102
 *
1103
 * See {@link goog.net.XhrIo#setWithCredentials}.
1104
 * @param {boolean} supportCrossDomain Whether cross domain XHRs are supported.
1105
 */
1106
goog.net.BrowserChannel.prototype.setSupportsCrossDomainXhrs = function(
1107
    supportCrossDomain) {
1108
  this.supportsCrossDomainXhrs_ = supportCrossDomain;
1109
};
1110

1111

1112
/**
1113
 * Returns the handler used for channel callback events.
1114
 *
1115
 * @return {goog.net.BrowserChannel.Handler} The handler.
1116
 */
1117
goog.net.BrowserChannel.prototype.getHandler = function() {
1118
  return this.handler_;
1119
};
1120

1121

1122
/**
1123
 * Sets the handler used for channel callback events.
1124
 * @param {goog.net.BrowserChannel.Handler} handler The handler to set.
1125
 */
1126
goog.net.BrowserChannel.prototype.setHandler = function(handler) {
1127
  this.handler_ = handler;
1128
};
1129

1130

1131
/**
1132
 * Returns whether the channel allows the use of a subdomain. There may be
1133
 * cases where this isn't allowed.
1134
 * @return {boolean} Whether a host prefix is allowed.
1135
 */
1136
goog.net.BrowserChannel.prototype.getAllowHostPrefix = function() {
1137
  return this.allowHostPrefix_;
1138
};
1139

1140

1141
/**
1142
 * Sets whether the channel allows the use of a subdomain. There may be cases
1143
 * where this isn't allowed, for example, logging in with troutboard where
1144
 * using a subdomain causes Apache to force the user to authenticate twice.
1145
 * @param {boolean} allowHostPrefix Whether a host prefix is allowed.
1146
 */
1147
goog.net.BrowserChannel.prototype.setAllowHostPrefix = function(
1148
    allowHostPrefix) {
1149
  this.allowHostPrefix_ = allowHostPrefix;
1150
};
1151

1152

1153
/**
1154
 * Returns whether the channel is buffered or not. This state is valid for
1155
 * querying only after the test connection has completed. This may be
1156
 * queried in the goog.net.BrowserChannel.okToMakeRequest() callback.
1157
 * A channel may be buffered if the test connection determines that
1158
 * a chunked response could not be sent down within a suitable time.
1159
 * @return {boolean} Whether the channel is buffered.
1160
 */
1161
goog.net.BrowserChannel.prototype.isBuffered = function() {
1162
  return !this.useChunked_;
1163
};
1164

1165

1166
/**
1167
 * Returns whether chunked mode is allowed. In certain debugging situations,
1168
 * it's useful for the application to have a way to disable chunked mode for a
1169
 * user.
1170

1171
 * @return {boolean} Whether chunked mode is allowed.
1172
 */
1173
goog.net.BrowserChannel.prototype.getAllowChunkedMode = function() {
1174
  return this.allowChunkedMode_;
1175
};
1176

1177

1178
/**
1179
 * Sets whether chunked mode is allowed. In certain debugging situations, it's
1180
 * useful for the application to have a way to disable chunked mode for a user.
1181
 * @param {boolean} allowChunkedMode  Whether chunked mode is allowed.
1182
 */
1183
goog.net.BrowserChannel.prototype.setAllowChunkedMode = function(
1184
    allowChunkedMode) {
1185
  this.allowChunkedMode_ = allowChunkedMode;
1186
};
1187

1188

1189
/**
1190
 * Sends a request to the server. The format of the request is a Map data
1191
 * structure of key/value pairs. These maps are then encoded in a format
1192
 * suitable for the wire and then reconstituted as a Map data structure that
1193
 * the server can process.
1194
 * @param {Object} map  The map to send.
1195
 * @param {?Object=} opt_context The context associated with the map.
1196
 */
1197
goog.net.BrowserChannel.prototype.sendMap = function(map, opt_context) {
1198
  if (this.state_ == goog.net.BrowserChannel.State.CLOSED) {
1199
    throw Error('Invalid operation: sending map when state is closed');
1200
  }
1201

1202
  // We can only send 1000 maps per POST, but typically we should never have
1203
  // that much to send, so warn if we exceed that (we still send all the maps).
1204
  if (this.outgoingMaps_.length ==
1205
      goog.net.BrowserChannel.MAX_MAPS_PER_REQUEST_) {
1206
    // severe() is temporary so that we get these uploaded and can figure out
1207
    // what's causing them. Afterwards can change to warning().
1208
    this.channelDebug_.severe(
1209
        'Already have ' + goog.net.BrowserChannel.MAX_MAPS_PER_REQUEST_ +
1210
        ' queued maps upon queueing ' + this.parser_.stringify(map));
1211
  }
1212

1213
  this.outgoingMaps_.push(
1214
      new goog.net.BrowserChannel.QueuedMap(
1215
          this.nextMapId_++, map, opt_context));
1216
  if (this.state_ == goog.net.BrowserChannel.State.OPENING ||
1217
      this.state_ == goog.net.BrowserChannel.State.OPENED) {
1218
    this.ensureForwardChannel_();
1219
  }
1220
};
1221

1222

1223
/**
1224
 * When set to true, this changes the behavior of the forward channel so it
1225
 * will not retry requests; it will fail after one network failure, and if
1226
 * there was already one network failure, the request will fail immediately.
1227
 * @param {boolean} failFast  Whether or not to fail fast.
1228
 */
1229
goog.net.BrowserChannel.prototype.setFailFast = function(failFast) {
1230
  this.failFast_ = failFast;
1231
  this.channelDebug_.info('setFailFast: ' + failFast);
1232
  if ((this.forwardChannelRequest_ || this.forwardChannelTimerId_) &&
1233
      this.forwardChannelRetryCount_ > this.getForwardChannelMaxRetries()) {
1234
    this.channelDebug_.info(
1235
        'Retry count ' + this.forwardChannelRetryCount_ + ' > new maxRetries ' +
1236
        this.getForwardChannelMaxRetries() + '. Fail immediately!');
1237
    if (this.forwardChannelRequest_) {
1238
      this.forwardChannelRequest_.cancel();
1239
      // Go through the standard onRequestComplete logic to expose the max-retry
1240
      // failure in the standard way.
1241
      this.onRequestComplete(this.forwardChannelRequest_);
1242
    } else {  // i.e., this.forwardChannelTimerId_
1243
      goog.global.clearTimeout(this.forwardChannelTimerId_);
1244
      this.forwardChannelTimerId_ = null;
1245
      // The error code from the last failed request is gone, so just use a
1246
      // generic one.
1247
      this.signalError_(goog.net.BrowserChannel.Error.REQUEST_FAILED);
1248
    }
1249
  }
1250
};
1251

1252

1253
/**
1254
 * @return {number} The max number of forward-channel retries, which will be 0
1255
 * in fail-fast mode.
1256
 */
1257
goog.net.BrowserChannel.prototype.getForwardChannelMaxRetries = function() {
1258
  return this.failFast_ ? 0 : this.forwardChannelMaxRetries_;
1259
};
1260

1261

1262
/**
1263
 * Sets the maximum number of attempts to connect to the server for forward
1264
 * channel requests.
1265
 * @param {number} retries The maximum number of attempts.
1266
 */
1267
goog.net.BrowserChannel.prototype.setForwardChannelMaxRetries = function(
1268
    retries) {
1269
  this.forwardChannelMaxRetries_ = retries;
1270
};
1271

1272

1273
/**
1274
 * Sets the timeout for a forward channel request.
1275
 * @param {number} timeoutMs The timeout in milliseconds.
1276
 */
1277
goog.net.BrowserChannel.prototype.setForwardChannelRequestTimeout = function(
1278
    timeoutMs) {
1279
  this.forwardChannelRequestTimeoutMs_ = timeoutMs;
1280
};
1281

1282

1283
/**
1284
 * @return {number} The max number of back-channel retries, which is a constant.
1285
 */
1286
goog.net.BrowserChannel.prototype.getBackChannelMaxRetries = function() {
1287
  // Back-channel retries is a constant.
1288
  return goog.net.BrowserChannel.BACK_CHANNEL_MAX_RETRIES;
1289
};
1290

1291

1292
/**
1293
 * Returns whether the channel is closed
1294
 * @return {boolean} true if the channel is closed.
1295
 */
1296
goog.net.BrowserChannel.prototype.isClosed = function() {
1297
  return this.state_ == goog.net.BrowserChannel.State.CLOSED;
1298
};
1299

1300

1301
/**
1302
 * Returns the browser channel state.
1303
 * @return {goog.net.BrowserChannel.State} The current state of the browser
1304
 * channel.
1305
 */
1306
goog.net.BrowserChannel.prototype.getState = function() {
1307
  return this.state_;
1308
};
1309

1310

1311
/**
1312
 * Return the last status code received for a request.
1313
 * @return {number} The last status code received for a request.
1314
 */
1315
goog.net.BrowserChannel.prototype.getLastStatusCode = function() {
1316
  return this.lastStatusCode_;
1317
};
1318

1319

1320
/**
1321
 * @return {number} The last array id received.
1322
 */
1323
goog.net.BrowserChannel.prototype.getLastArrayId = function() {
1324
  return this.lastArrayId_;
1325
};
1326

1327

1328
/**
1329
 * Returns whether there are outstanding requests servicing the channel.
1330
 * @return {boolean} true if there are outstanding requests.
1331
 */
1332
goog.net.BrowserChannel.prototype.hasOutstandingRequests = function() {
1333
  return this.outstandingRequests_() != 0;
1334
};
1335

1336

1337
/**
1338
 * Sets a new parser for the response payload.
1339
 * @param {!goog.string.Parser} parser Parser.
1340
 */
1341
goog.net.BrowserChannel.prototype.setParser = function(parser) {
1342
  this.parser_ = parser;
1343
};
1344

1345

1346
/**
1347
 * Returns the number of outstanding requests.
1348
 * @return {number} The number of outstanding requests to the server.
1349
 * @private
1350
 */
1351
goog.net.BrowserChannel.prototype.outstandingRequests_ = function() {
1352
  var count = 0;
1353
  if (this.backChannelRequest_) {
1354
    count++;
1355
  }
1356
  if (this.forwardChannelRequest_) {
1357
    count++;
1358
  }
1359
  return count;
1360
};
1361

1362

1363
/**
1364
 * Ensures that a forward channel request is scheduled.
1365
 * @private
1366
 */
1367
goog.net.BrowserChannel.prototype.ensureForwardChannel_ = function() {
1368
  if (this.forwardChannelRequest_) {
1369
    // connection in process - no need to start a new request
1370
    return;
1371
  }
1372

1373
  if (this.forwardChannelTimerId_) {
1374
    // no need to start a new request - one is already scheduled
1375
    return;
1376
  }
1377

1378
  this.forwardChannelTimerId_ = goog.net.BrowserChannel.setTimeout(
1379
      goog.bind(this.onStartForwardChannelTimer_, this), 0);
1380
  this.forwardChannelRetryCount_ = 0;
1381
};
1382

1383

1384
/**
1385
 * Schedules a forward-channel retry for the specified request, unless the max
1386
 * retries has been reached.
1387
 * @param {goog.net.ChannelRequest} request The failed request to retry.
1388
 * @return {boolean} true iff a retry was scheduled.
1389
 * @private
1390
 */
1391
goog.net.BrowserChannel.prototype.maybeRetryForwardChannel_ = function(
1392
    request) {
1393
  if (this.forwardChannelRequest_ || this.forwardChannelTimerId_) {
1394
    // Should be impossible to be called in this state.
1395
    this.channelDebug_.severe('Request already in progress');
1396
    return false;
1397
  }
1398

1399
  if (this.state_ == goog.net.BrowserChannel.State.INIT ||  // no retry open_()
1400
      (this.forwardChannelRetryCount_ >= this.getForwardChannelMaxRetries())) {
1401
    return false;
1402
  }
1403

1404
  this.channelDebug_.debug('Going to retry POST');
1405

1406
  this.forwardChannelTimerId_ = goog.net.BrowserChannel.setTimeout(
1407
      goog.bind(this.onStartForwardChannelTimer_, this, request),
1408
      this.getRetryTime_(this.forwardChannelRetryCount_));
1409
  this.forwardChannelRetryCount_++;
1410
  return true;
1411
};
1412

1413

1414
/**
1415
 * Timer callback for ensureForwardChannel
1416
 * @param {goog.net.ChannelRequest=} opt_retryRequest A failed request to retry.
1417
 * @private
1418
 */
1419
goog.net.BrowserChannel.prototype.onStartForwardChannelTimer_ = function(
1420
    opt_retryRequest) {
1421
  this.forwardChannelTimerId_ = null;
1422
  this.startForwardChannel_(opt_retryRequest);
1423
};
1424

1425

1426
/**
1427
 * Begins a new forward channel operation to the server.
1428
 * @param {goog.net.ChannelRequest=} opt_retryRequest A failed request to retry.
1429
 * @private
1430
 */
1431
goog.net.BrowserChannel.prototype.startForwardChannel_ = function(
1432
    opt_retryRequest) {
1433
  this.channelDebug_.debug('startForwardChannel_');
1434
  if (!this.okToMakeRequest_()) {
1435
    return;  // channel is cancelled
1436
  } else if (this.state_ == goog.net.BrowserChannel.State.INIT) {
1437
    if (opt_retryRequest) {
1438
      this.channelDebug_.severe('Not supposed to retry the open');
1439
      return;
1440
    }
1441
    this.open_();
1442
    this.state_ = goog.net.BrowserChannel.State.OPENING;
1443
  } else if (this.state_ == goog.net.BrowserChannel.State.OPENED) {
1444
    if (opt_retryRequest) {
1445
      this.makeForwardChannelRequest_(opt_retryRequest);
1446
      return;
1447
    }
1448

1449
    if (this.outgoingMaps_.length == 0) {
1450
      this.channelDebug_.debug(
1451
          'startForwardChannel_ returned: ' +
1452
          'nothing to send');
1453
      // no need to start a new forward channel request
1454
      return;
1455
    }
1456

1457
    if (this.forwardChannelRequest_) {
1458
      // Should be impossible to be called in this state.
1459
      this.channelDebug_.severe(
1460
          'startForwardChannel_ returned: ' +
1461
          'connection already in progress');
1462
      return;
1463
    }
1464

1465
    this.makeForwardChannelRequest_();
1466
    this.channelDebug_.debug('startForwardChannel_ finished, sent request');
1467
  }
1468
};
1469

1470

1471
/**
1472
 * Establishes a new channel session with the the server.
1473
 * @private
1474
 */
1475
goog.net.BrowserChannel.prototype.open_ = function() {
1476
  this.channelDebug_.debug('open_()');
1477
  this.nextRid_ = Math.floor(Math.random() * 100000);
1478

1479
  var rid = this.nextRid_++;
1480
  var request = goog.net.BrowserChannel.createChannelRequest(
1481
      this, this.channelDebug_, '', rid);
1482
  request.setExtraHeaders(this.extraHeaders_);
1483
  var requestText = this.dequeueOutgoingMaps_();
1484
  var uri = this.forwardChannelUri_.clone();
1485
  uri.setParameterValue('RID', rid);
1486
  if (this.clientVersion_) {
1487
    uri.setParameterValue('CVER', this.clientVersion_);
1488
  }
1489

1490
  // Add the reconnect parameters.
1491
  this.addAdditionalParams_(uri);
1492

1493
  request.xmlHttpPost(uri, requestText, true);
1494
  this.forwardChannelRequest_ = request;
1495
};
1496

1497

1498
/**
1499
 * Makes a forward channel request using XMLHTTP.
1500
 * @param {goog.net.ChannelRequest=} opt_retryRequest A failed request to retry.
1501
 * @private
1502
 */
1503
goog.net.BrowserChannel.prototype.makeForwardChannelRequest_ = function(
1504
    opt_retryRequest) {
1505
  var rid;
1506
  var requestText;
1507
  if (opt_retryRequest) {
1508
    if (this.channelVersion_ > 6) {
1509
      // In version 7 and up we can tack on new arrays to a retry.
1510
      this.requeuePendingMaps_();
1511
      rid = this.nextRid_ - 1;  // Must use last RID
1512
      requestText = this.dequeueOutgoingMaps_();
1513
    } else {
1514
      // TODO(user): Remove this code and the opt_retryRequest passing
1515
      // once server-side support for ver 7 is ubiquitous.
1516
      rid = opt_retryRequest.getRequestId();
1517
      requestText = /** @type {string} */ (opt_retryRequest.getPostData());
1518
    }
1519
  } else {
1520
    rid = this.nextRid_++;
1521
    requestText = this.dequeueOutgoingMaps_();
1522
  }
1523

1524
  var uri = this.forwardChannelUri_.clone();
1525
  uri.setParameterValue('SID', this.sid_);
1526
  uri.setParameterValue('RID', rid);
1527
  uri.setParameterValue('AID', this.lastArrayId_);
1528
  // Add the additional reconnect parameters.
1529
  this.addAdditionalParams_(uri);
1530

1531
  var request = goog.net.BrowserChannel.createChannelRequest(
1532
      this, this.channelDebug_, this.sid_, rid,
1533
      this.forwardChannelRetryCount_ + 1);
1534
  request.setExtraHeaders(this.extraHeaders_);
1535

1536
  // randomize from 50%-100% of the forward channel timeout to avoid
1537
  // a big hit if servers happen to die at once.
1538
  request.setTimeout(
1539
      Math.round(this.forwardChannelRequestTimeoutMs_ * 0.50) +
1540
      Math.round(this.forwardChannelRequestTimeoutMs_ * 0.50 * Math.random()));
1541
  this.forwardChannelRequest_ = request;
1542
  request.xmlHttpPost(uri, requestText, true);
1543
};
1544

1545

1546
/**
1547
 * Adds the additional parameters from the handler to the given URI.
1548
 * @param {goog.Uri} uri The URI to add the parameters to.
1549
 * @private
1550
 */
1551
goog.net.BrowserChannel.prototype.addAdditionalParams_ = function(uri) {
1552
  // Add the additional reconnect parameters as needed.
1553
  if (this.handler_) {
1554
    var params = this.handler_.getAdditionalParams(this);
1555
    if (params) {
1556
      goog.object.forEach(
1557
          params, function(value, key) { uri.setParameterValue(key, value); });
1558
    }
1559
  }
1560
};
1561

1562

1563
/**
1564
 * Returns the request text from the outgoing maps and resets it.
1565
 * @return {string} The encoded request text created from all the currently
1566
 *                  queued outgoing maps.
1567
 * @private
1568
 */
1569
goog.net.BrowserChannel.prototype.dequeueOutgoingMaps_ = function() {
1570
  var count = Math.min(
1571
      this.outgoingMaps_.length, goog.net.BrowserChannel.MAX_MAPS_PER_REQUEST_);
1572
  var sb = ['count=' + count];
1573
  var offset;
1574
  if (this.channelVersion_ > 6 && count > 0) {
1575
    // To save a bit of bandwidth, specify the base mapId and the rest as
1576
    // offsets from it.
1577
    offset = this.outgoingMaps_[0].mapId;
1578
    sb.push('ofs=' + offset);
1579
  } else {
1580
    offset = 0;
1581
  }
1582
  for (var i = 0; i < count; i++) {
1583
    var mapId = this.outgoingMaps_[i].mapId;
1584
    var map = this.outgoingMaps_[i].map;
1585
    if (this.channelVersion_ <= 6) {
1586
      // Map IDs were not used in ver 6 and before, just indexes in the request.
1587
      mapId = i;
1588
    } else {
1589
      mapId -= offset;
1590
    }
1591
    try {
1592
      goog.object.forEach(map, function(value, key, coll) {
1593
        sb.push('req' + mapId + '_' + key + '=' + encodeURIComponent(value));
1594
      });
1595
    } catch (ex) {
1596
      // We send a map here because lots of the retry logic relies on map IDs,
1597
      // so we have to send something.
1598
      sb.push(
1599
          'req' + mapId + '_' +
1600
          'type' +
1601
          '=' + encodeURIComponent('_badmap'));
1602
      if (this.handler_) {
1603
        this.handler_.badMapError(this, map);
1604
      }
1605
    }
1606
  }
1607
  this.pendingMaps_ =
1608
      this.pendingMaps_.concat(this.outgoingMaps_.splice(0, count));
1609
  return sb.join('&');
1610
};
1611

1612

1613
/**
1614
 * Requeues unacknowledged sent arrays for retransmission in the next forward
1615
 * channel request.
1616
 * @private
1617
 */
1618
goog.net.BrowserChannel.prototype.requeuePendingMaps_ = function() {
1619
  this.outgoingMaps_ = this.pendingMaps_.concat(this.outgoingMaps_);
1620
  this.pendingMaps_.length = 0;
1621
};
1622

1623

1624
/**
1625
 * Ensures there is a backchannel request for receiving data from the server.
1626
 * @private
1627
 */
1628
goog.net.BrowserChannel.prototype.ensureBackChannel_ = function() {
1629
  if (this.backChannelRequest_) {
1630
    // already have one
1631
    return;
1632
  }
1633

1634
  if (this.backChannelTimerId_) {
1635
    // no need to start a new request - one is already scheduled
1636
    return;
1637
  }
1638

1639
  this.backChannelAttemptId_ = 1;
1640
  this.backChannelTimerId_ = goog.net.BrowserChannel.setTimeout(
1641
      goog.bind(this.onStartBackChannelTimer_, this), 0);
1642
  this.backChannelRetryCount_ = 0;
1643
};
1644

1645

1646
/**
1647
 * Schedules a back-channel retry, unless the max retries has been reached.
1648
 * @return {boolean} true iff a retry was scheduled.
1649
 * @private
1650
 */
1651
goog.net.BrowserChannel.prototype.maybeRetryBackChannel_ = function() {
1652
  if (this.backChannelRequest_ || this.backChannelTimerId_) {
1653
    // Should be impossible to be called in this state.
1654
    this.channelDebug_.severe('Request already in progress');
1655
    return false;
1656
  }
1657

1658
  if (this.backChannelRetryCount_ >= this.getBackChannelMaxRetries()) {
1659
    return false;
1660
  }
1661

1662
  this.channelDebug_.debug('Going to retry GET');
1663

1664
  this.backChannelAttemptId_++;
1665
  this.backChannelTimerId_ = goog.net.BrowserChannel.setTimeout(
1666
      goog.bind(this.onStartBackChannelTimer_, this),
1667
      this.getRetryTime_(this.backChannelRetryCount_));
1668
  this.backChannelRetryCount_++;
1669
  return true;
1670
};
1671

1672

1673
/**
1674
 * Timer callback for ensureBackChannel_.
1675
 * @private
1676
 */
1677
goog.net.BrowserChannel.prototype.onStartBackChannelTimer_ = function() {
1678
  this.backChannelTimerId_ = null;
1679
  this.startBackChannel_();
1680
};
1681

1682

1683
/**
1684
 * Begins a new back channel operation to the server.
1685
 * @private
1686
 */
1687
goog.net.BrowserChannel.prototype.startBackChannel_ = function() {
1688
  if (!this.okToMakeRequest_()) {
1689
    // channel is cancelled
1690
    return;
1691
  }
1692

1693
  this.channelDebug_.debug('Creating new HttpRequest');
1694
  this.backChannelRequest_ = goog.net.BrowserChannel.createChannelRequest(
1695
      this, this.channelDebug_, this.sid_, 'rpc', this.backChannelAttemptId_);
1696
  this.backChannelRequest_.setExtraHeaders(this.extraHeaders_);
1697
  this.backChannelRequest_.setReadyStateChangeThrottle(
1698
      this.readyStateChangeThrottleMs_);
1699
  var uri = this.backChannelUri_.clone();
1700
  uri.setParameterValue('RID', 'rpc');
1701
  uri.setParameterValue('SID', this.sid_);
1702
  uri.setParameterValue('CI', this.useChunked_ ? '0' : '1');
1703
  uri.setParameterValue('AID', this.lastArrayId_);
1704

1705
  // Add the reconnect parameters.
1706
  this.addAdditionalParams_(uri);
1707

1708
  if (!goog.net.ChannelRequest.supportsXhrStreaming()) {
1709
    uri.setParameterValue('TYPE', 'html');
1710
    this.backChannelRequest_.tridentGet(uri, Boolean(this.hostPrefix_));
1711
  } else {
1712
    uri.setParameterValue('TYPE', 'xmlhttp');
1713
    this.backChannelRequest_.xmlHttpGet(
1714
        uri, true /* decodeChunks */, this.hostPrefix_,
1715
        false /* opt_noClose */);
1716
  }
1717
  this.channelDebug_.debug('New Request created');
1718
};
1719

1720

1721
/**
1722
 * Gives the handler a chance to return an error code and stop channel
1723
 * execution. A handler might want to do this to check that the user is still
1724
 * logged in, for example.
1725
 * @private
1726
 * @return {boolean} If it's OK to make a request.
1727
 */
1728
goog.net.BrowserChannel.prototype.okToMakeRequest_ = function() {
1729
  if (this.handler_) {
1730
    var result = this.handler_.okToMakeRequest(this);
1731
    if (result != goog.net.BrowserChannel.Error.OK) {
1732
      this.channelDebug_.debug(
1733
          'Handler returned error code from ' +
1734
          'okToMakeRequest');
1735
      this.signalError_(result);
1736
      return false;
1737
    }
1738
  }
1739
  return true;
1740
};
1741

1742

1743
/**
1744
 * Callback from BrowserTestChannel for when the channel is finished.
1745
 * @param {goog.net.BrowserTestChannel} testChannel The BrowserTestChannel.
1746
 * @param {boolean} useChunked  Whether we can chunk responses.
1747
 */
1748
goog.net.BrowserChannel.prototype.testConnectionFinished = function(
1749
    testChannel, useChunked) {
1750
  this.channelDebug_.debug('Test Connection Finished');
1751

1752
  this.useChunked_ = this.allowChunkedMode_ && useChunked;
1753
  this.lastStatusCode_ = testChannel.getLastStatusCode();
1754
  // When using asynchronous test, the channel is already open by connect().
1755
  if (!this.asyncTest_) {
1756
    this.connectChannel_();
1757
  }
1758
};
1759

1760

1761
/**
1762
 * Callback from BrowserTestChannel for when the channel has an error.
1763
 * @param {goog.net.BrowserTestChannel} testChannel The BrowserTestChannel.
1764
 * @param {goog.net.ChannelRequest.Error} errorCode  The error code of the
1765
       failure.
1766
 */
1767
goog.net.BrowserChannel.prototype.testConnectionFailure = function(
1768
    testChannel, errorCode) {
1769
  this.channelDebug_.debug('Test Connection Failed');
1770
  this.lastStatusCode_ = testChannel.getLastStatusCode();
1771
  this.signalError_(goog.net.BrowserChannel.Error.REQUEST_FAILED);
1772
};
1773

1774

1775
/**
1776
 * Callback from BrowserTestChannel for when the channel is blocked.
1777
 * @param {goog.net.BrowserTestChannel} testChannel The BrowserTestChannel.
1778
 */
1779
goog.net.BrowserChannel.prototype.testConnectionBlocked = function(
1780
    testChannel) {
1781
  this.channelDebug_.debug('Test Connection Blocked');
1782
  this.lastStatusCode_ = this.connectionTest_.getLastStatusCode();
1783
  this.signalError_(goog.net.BrowserChannel.Error.BLOCKED);
1784
};
1785

1786

1787
/**
1788
 * Callback from ChannelRequest for when new data is received
1789
 * @param {goog.net.ChannelRequest} request  The request object.
1790
 * @param {string} responseText The text of the response.
1791
 */
1792
goog.net.BrowserChannel.prototype.onRequestData = function(
1793
    request, responseText) {
1794
  if (this.state_ == goog.net.BrowserChannel.State.CLOSED ||
1795
      (this.backChannelRequest_ != request &&
1796
       this.forwardChannelRequest_ != request)) {
1797
    // either CLOSED or a request we don't know about (perhaps an old request)
1798
    return;
1799
  }
1800
  this.lastStatusCode_ = request.getLastStatusCode();
1801

1802
  if (this.forwardChannelRequest_ == request &&
1803
      this.state_ == goog.net.BrowserChannel.State.OPENED) {
1804
    if (this.channelVersion_ > 7) {
1805
      var response;
1806
      try {
1807
        response = this.parser_.parse(responseText);
1808
      } catch (ex) {
1809
        response = null;
1810
      }
1811
      if (goog.isArray(response) && response.length == 3) {
1812
        this.handlePostResponse_(response);
1813
      } else {
1814
        this.channelDebug_.debug('Bad POST response data returned');
1815
        this.signalError_(goog.net.BrowserChannel.Error.BAD_RESPONSE);
1816
      }
1817
    } else if (responseText != goog.net.ChannelDebug.MAGIC_RESPONSE_COOKIE) {
1818
      this.channelDebug_.debug(
1819
          'Bad data returned - missing/invald ' +
1820
          'magic cookie');
1821
      this.signalError_(goog.net.BrowserChannel.Error.BAD_RESPONSE);
1822
    }
1823
  } else {
1824
    if (this.backChannelRequest_ == request) {
1825
      this.clearDeadBackchannelTimer_();
1826
    }
1827
    if (!goog.string.isEmptyOrWhitespace(responseText)) {
1828
      var response = this.parser_.parse(responseText);
1829
      goog.asserts.assert(goog.isArray(response));
1830
      this.onInput_(/** @type {!Array<?>} */ (response));
1831
    }
1832
  }
1833
};
1834

1835

1836
/**
1837
 * Handles a POST response from the server.
1838
 * @param {Array<number>} responseValues The key value pairs in the POST
1839
 *     response.
1840
 * @private
1841
 */
1842
goog.net.BrowserChannel.prototype.handlePostResponse_ = function(
1843
    responseValues) {
1844
  // The first response value is set to 0 if server is missing backchannel.
1845
  if (responseValues[0] == 0) {
1846
    this.handleBackchannelMissing_();
1847
    return;
1848
  }
1849
  this.lastPostResponseArrayId_ = responseValues[1];
1850
  var outstandingArrays = this.lastPostResponseArrayId_ - this.lastArrayId_;
1851
  if (0 < outstandingArrays) {
1852
    var numOutstandingBackchannelBytes = responseValues[2];
1853
    this.channelDebug_.debug(
1854
        numOutstandingBackchannelBytes + ' bytes (in ' + outstandingArrays +
1855
        ' arrays) are outstanding on the BackChannel');
1856
    if (!this.shouldRetryBackChannel_(numOutstandingBackchannelBytes)) {
1857
      return;
1858
    }
1859
    if (!this.deadBackChannelTimerId_) {
1860
      // We expect to receive data within 2 RTTs or we retry the backchannel.
1861
      this.deadBackChannelTimerId_ = goog.net.BrowserChannel.setTimeout(
1862
          goog.bind(this.onBackChannelDead_, this),
1863
          2 * goog.net.BrowserChannel.RTT_ESTIMATE);
1864
    }
1865
  }
1866
};
1867

1868

1869
/**
1870
 * Handles a POST response from the server telling us that it has detected that
1871
 * we have no hanging GET connection.
1872
 * @private
1873
 */
1874
goog.net.BrowserChannel.prototype.handleBackchannelMissing_ = function() {
1875
  // As long as the back channel was started before the POST was sent,
1876
  // we should retry the backchannel. We give a slight buffer of RTT_ESTIMATE
1877
  // so as not to excessively retry the backchannel
1878
  this.channelDebug_.debug('Server claims our backchannel is missing.');
1879
  if (this.backChannelTimerId_) {
1880
    this.channelDebug_.debug('But we are currently starting the request.');
1881
    return;
1882
  } else if (!this.backChannelRequest_) {
1883
    this.channelDebug_.warning('We do not have a BackChannel established');
1884
  } else if (
1885
      this.backChannelRequest_.getRequestStartTime() +
1886
          goog.net.BrowserChannel.RTT_ESTIMATE <
1887
      this.forwardChannelRequest_.getRequestStartTime()) {
1888
    this.clearDeadBackchannelTimer_();
1889
    this.backChannelRequest_.cancel();
1890
    this.backChannelRequest_ = null;
1891
  } else {
1892
    return;
1893
  }
1894
  this.maybeRetryBackChannel_();
1895
  goog.net.BrowserChannel.notifyStatEvent(
1896
      goog.net.BrowserChannel.Stat.BACKCHANNEL_MISSING);
1897
};
1898

1899

1900
/**
1901
 * Determines whether we should start the process of retrying a possibly
1902
 * dead backchannel.
1903
 * @param {number} outstandingBytes The number of bytes for which the server has
1904
 *     not yet received acknowledgement.
1905
 * @return {boolean} Whether to start the backchannel retry timer.
1906
 * @private
1907
 */
1908
goog.net.BrowserChannel.prototype.shouldRetryBackChannel_ = function(
1909
    outstandingBytes) {
1910
  // Not too many outstanding bytes, not buffered and not after a retry.
1911
  return outstandingBytes <
1912
      goog.net.BrowserChannel.OUTSTANDING_DATA_BACKCHANNEL_RETRY_CUTOFF &&
1913
      !this.isBuffered() && this.backChannelRetryCount_ == 0;
1914
};
1915

1916

1917
/**
1918
 * Decides which host prefix should be used, if any.  If there is a handler,
1919
 * allows the handler to validate a host prefix provided by the server, and
1920
 * optionally override it.
1921
 * @param {?string} serverHostPrefix The host prefix provided by the server.
1922
 * @return {?string} The host prefix to actually use, if any. Will return null
1923
 *     if the use of host prefixes was disabled via setAllowHostPrefix().
1924
 */
1925
goog.net.BrowserChannel.prototype.correctHostPrefix = function(
1926
    serverHostPrefix) {
1927
  if (this.allowHostPrefix_) {
1928
    if (this.handler_) {
1929
      return this.handler_.correctHostPrefix(serverHostPrefix);
1930
    }
1931
    return serverHostPrefix;
1932
  }
1933
  return null;
1934
};
1935

1936

1937
/**
1938
 * Handles the timer that indicates that our backchannel is no longer able to
1939
 * successfully receive data from the server.
1940
 * @private
1941
 */
1942
goog.net.BrowserChannel.prototype.onBackChannelDead_ = function() {
1943
  if (goog.isDefAndNotNull(this.deadBackChannelTimerId_)) {
1944
    this.deadBackChannelTimerId_ = null;
1945
    this.backChannelRequest_.cancel();
1946
    this.backChannelRequest_ = null;
1947
    this.maybeRetryBackChannel_();
1948
    goog.net.BrowserChannel.notifyStatEvent(
1949
        goog.net.BrowserChannel.Stat.BACKCHANNEL_DEAD);
1950
  }
1951
};
1952

1953

1954
/**
1955
 * Clears the timer that indicates that our backchannel is no longer able to
1956
 * successfully receive data from the server.
1957
 * @private
1958
 */
1959
goog.net.BrowserChannel.prototype.clearDeadBackchannelTimer_ = function() {
1960
  if (goog.isDefAndNotNull(this.deadBackChannelTimerId_)) {
1961
    goog.global.clearTimeout(this.deadBackChannelTimerId_);
1962
    this.deadBackChannelTimerId_ = null;
1963
  }
1964
};
1965

1966

1967
/**
1968
 * Returns whether or not the given error/status combination is fatal or not.
1969
 * On fatal errors we immediately close the session rather than retrying the
1970
 * failed request.
1971
 * @param {goog.net.ChannelRequest.Error?} error The error code for the failed
1972
 * request.
1973
 * @param {number} statusCode The last HTTP status code.
1974
 * @return {boolean} Whether or not the error is fatal.
1975
 * @private
1976
 */
1977
goog.net.BrowserChannel.isFatalError_ = function(error, statusCode) {
1978
  return error == goog.net.ChannelRequest.Error.UNKNOWN_SESSION_ID ||
1979
      error == goog.net.ChannelRequest.Error.ACTIVE_X_BLOCKED ||
1980
      (error == goog.net.ChannelRequest.Error.STATUS && statusCode > 0);
1981
};
1982

1983

1984
/**
1985
 * Callback from ChannelRequest that indicates a request has completed.
1986
 * @param {goog.net.ChannelRequest} request  The request object.
1987
 */
1988
goog.net.BrowserChannel.prototype.onRequestComplete = function(request) {
1989
  this.channelDebug_.debug('Request complete');
1990
  var type;
1991
  if (this.backChannelRequest_ == request) {
1992
    this.clearDeadBackchannelTimer_();
1993
    this.backChannelRequest_ = null;
1994
    type = goog.net.BrowserChannel.ChannelType_.BACK_CHANNEL;
1995
  } else if (this.forwardChannelRequest_ == request) {
1996
    this.forwardChannelRequest_ = null;
1997
    type = goog.net.BrowserChannel.ChannelType_.FORWARD_CHANNEL;
1998
  } else {
1999
    // return if it was an old request from a previous session
2000
    return;
2001
  }
2002

2003
  this.lastStatusCode_ = request.getLastStatusCode();
2004

2005
  if (this.state_ == goog.net.BrowserChannel.State.CLOSED) {
2006
    return;
2007
  }
2008

2009
  if (request.getSuccess()) {
2010
    // Yay!
2011
    if (type == goog.net.BrowserChannel.ChannelType_.FORWARD_CHANNEL) {
2012
      var size = request.getPostData() ? request.getPostData().length : 0;
2013
      goog.net.BrowserChannel.notifyTimingEvent(
2014
          size, goog.now() - request.getRequestStartTime(),
2015
          this.forwardChannelRetryCount_);
2016
      this.ensureForwardChannel_();
2017
      this.onSuccess_();
2018
      this.pendingMaps_.length = 0;
2019
    } else {  // i.e., back-channel
2020
      this.ensureBackChannel_();
2021
    }
2022
    return;
2023
  }
2024
  // Else unsuccessful. Fall through.
2025

2026
  var lastError = request.getLastError();
2027
  if (!goog.net.BrowserChannel.isFatalError_(lastError, this.lastStatusCode_)) {
2028
    // Maybe retry.
2029
    this.channelDebug_.debug(
2030
        'Maybe retrying, last error: ' +
2031
        goog.net.ChannelRequest.errorStringFromCode(
2032
            /** @type {goog.net.ChannelRequest.Error} */ (lastError),
2033
            this.lastStatusCode_));
2034
    if (type == goog.net.BrowserChannel.ChannelType_.FORWARD_CHANNEL) {
2035
      if (this.maybeRetryForwardChannel_(request)) {
2036
        return;
2037
      }
2038
    }
2039
    if (type == goog.net.BrowserChannel.ChannelType_.BACK_CHANNEL) {
2040
      if (this.maybeRetryBackChannel_()) {
2041
        return;
2042
      }
2043
    }
2044
    // Else exceeded max retries. Fall through.
2045
    this.channelDebug_.debug('Exceeded max number of retries');
2046
  } else {
2047
    // Else fatal error. Fall through and mark the pending maps as failed.
2048
    this.channelDebug_.debug('Not retrying due to error type');
2049
  }
2050

2051

2052
  // Can't save this session. :(
2053
  this.channelDebug_.debug('Error: HTTP request failed');
2054
  switch (lastError) {
2055
    case goog.net.ChannelRequest.Error.NO_DATA:
2056
      this.signalError_(goog.net.BrowserChannel.Error.NO_DATA);
2057
      break;
2058
    case goog.net.ChannelRequest.Error.BAD_DATA:
2059
      this.signalError_(goog.net.BrowserChannel.Error.BAD_DATA);
2060
      break;
2061
    case goog.net.ChannelRequest.Error.UNKNOWN_SESSION_ID:
2062
      this.signalError_(goog.net.BrowserChannel.Error.UNKNOWN_SESSION_ID);
2063
      break;
2064
    case goog.net.ChannelRequest.Error.ACTIVE_X_BLOCKED:
2065
      this.signalError_(goog.net.BrowserChannel.Error.ACTIVE_X_BLOCKED);
2066
      break;
2067
    default:
2068
      this.signalError_(goog.net.BrowserChannel.Error.REQUEST_FAILED);
2069
      break;
2070
  }
2071
};
2072

2073

2074
/**
2075
 * @param {number} retryCount Number of retries so far.
2076
 * @return {number} Time in ms before firing next retry request.
2077
 * @private
2078
 */
2079
goog.net.BrowserChannel.prototype.getRetryTime_ = function(retryCount) {
2080
  var retryTime = this.baseRetryDelayMs_ +
2081
      Math.floor(Math.random() * this.retryDelaySeedMs_);
2082
  if (!this.isActive()) {
2083
    this.channelDebug_.debug('Inactive channel');
2084
    retryTime =
2085
        retryTime * goog.net.BrowserChannel.INACTIVE_CHANNEL_RETRY_FACTOR;
2086
  }
2087
  // Backoff for subsequent retries
2088
  retryTime = retryTime * retryCount;
2089
  return retryTime;
2090
};
2091

2092

2093
/**
2094
 * @param {number} baseDelayMs The base part of the retry delay, in ms.
2095
 * @param {number} delaySeedMs A random delay between 0 and this is added to
2096
 *     the base part.
2097
 */
2098
goog.net.BrowserChannel.prototype.setRetryDelay = function(
2099
    baseDelayMs, delaySeedMs) {
2100
  this.baseRetryDelayMs_ = baseDelayMs;
2101
  this.retryDelaySeedMs_ = delaySeedMs;
2102
};
2103

2104

2105
/**
2106
 * Processes the data returned by the server.
2107
 * @param {!Array<!Array<?>>} respArray The response array returned
2108
 *     by the server.
2109
 * @private
2110
 */
2111
goog.net.BrowserChannel.prototype.onInput_ = function(respArray) {
2112
  var batch =
2113
      this.handler_ && this.handler_.channelHandleMultipleArrays ? [] : null;
2114
  for (var i = 0; i < respArray.length; i++) {
2115
    var nextArray = respArray[i];
2116
    this.lastArrayId_ = nextArray[0];
2117
    nextArray = nextArray[1];
2118
    if (this.state_ == goog.net.BrowserChannel.State.OPENING) {
2119
      if (nextArray[0] == 'c') {
2120
        this.sid_ = nextArray[1];
2121
        this.hostPrefix_ = this.correctHostPrefix(nextArray[2]);
2122
        var negotiatedVersion = nextArray[3];
2123
        if (goog.isDefAndNotNull(negotiatedVersion)) {
2124
          this.channelVersion_ = negotiatedVersion;
2125
        } else {
2126
          // Servers prior to version 7 did not send this, so assume version 6.
2127
          this.channelVersion_ = 6;
2128
        }
2129
        this.state_ = goog.net.BrowserChannel.State.OPENED;
2130
        if (this.handler_) {
2131
          this.handler_.channelOpened(this);
2132
        }
2133
        this.backChannelUri_ = this.getBackChannelUri(
2134
            this.hostPrefix_, /** @type {string} */ (this.path_));
2135
        // Open connection to receive data
2136
        this.ensureBackChannel_();
2137
      } else if (nextArray[0] == 'stop') {
2138
        this.signalError_(goog.net.BrowserChannel.Error.STOP);
2139
      }
2140
    } else if (this.state_ == goog.net.BrowserChannel.State.OPENED) {
2141
      if (nextArray[0] == 'stop') {
2142
        if (batch && !goog.array.isEmpty(batch)) {
2143
          this.handler_.channelHandleMultipleArrays(this, batch);
2144
          batch.length = 0;
2145
        }
2146
        this.signalError_(goog.net.BrowserChannel.Error.STOP);
2147
      } else if (nextArray[0] == 'noop') {
2148
        // ignore - noop to keep connection happy
2149
      } else {
2150
        if (batch) {
2151
          batch.push(nextArray);
2152
        } else if (this.handler_) {
2153
          this.handler_.channelHandleArray(this, nextArray);
2154
        }
2155
      }
2156
      // We have received useful data on the back-channel, so clear its retry
2157
      // count. We do this because back-channels by design do not complete
2158
      // quickly, so on a flaky connection we could have many fail to complete
2159
      // fully but still deliver a lot of data before they fail. We don't want
2160
      // to count such failures towards the retry limit, because we don't want
2161
      // to give up on a session if we can still receive data.
2162
      this.backChannelRetryCount_ = 0;
2163
    }
2164
  }
2165
  if (batch && !goog.array.isEmpty(batch)) {
2166
    this.handler_.channelHandleMultipleArrays(this, batch);
2167
  }
2168
};
2169

2170

2171
/**
2172
 * Helper to ensure the BrowserChannel is in the expected state.
2173
 * @param {...number} var_args The channel must be in one of the indicated
2174
 *     states.
2175
 * @private
2176
 */
2177
goog.net.BrowserChannel.prototype.ensureInState_ = function(var_args) {
2178
  if (!goog.array.contains(arguments, this.state_)) {
2179
    throw Error('Unexpected channel state: ' + this.state_);
2180
  }
2181
};
2182

2183

2184
/**
2185
 * Signals an error has occurred.
2186
 * @param {goog.net.BrowserChannel.Error} error  The error code for the failure.
2187
 * @private
2188
 */
2189
goog.net.BrowserChannel.prototype.signalError_ = function(error) {
2190
  this.channelDebug_.info('Error code ' + error);
2191
  if (error == goog.net.BrowserChannel.Error.REQUEST_FAILED ||
2192
      error == goog.net.BrowserChannel.Error.BLOCKED) {
2193
    // Ping google to check if it's a server error or user's network error.
2194
    var imageUri = null;
2195
    if (this.handler_) {
2196
      imageUri = this.handler_.getNetworkTestImageUri(this);
2197
    }
2198
    goog.net.tmpnetwork.testGoogleCom(
2199
        goog.bind(this.testGoogleComCallback_, this), imageUri);
2200
  } else {
2201
    goog.net.BrowserChannel.notifyStatEvent(
2202
        goog.net.BrowserChannel.Stat.ERROR_OTHER);
2203
  }
2204
  this.onError_(error);
2205
};
2206

2207

2208
/**
2209
 * Callback for testGoogleCom during error handling.
2210
 * @param {boolean} networkUp Whether the network is up.
2211
 * @private
2212
 */
2213
goog.net.BrowserChannel.prototype.testGoogleComCallback_ = function(networkUp) {
2214
  if (networkUp) {
2215
    this.channelDebug_.info('Successfully pinged google.com');
2216
    goog.net.BrowserChannel.notifyStatEvent(
2217
        goog.net.BrowserChannel.Stat.ERROR_OTHER);
2218
  } else {
2219
    this.channelDebug_.info('Failed to ping google.com');
2220
    goog.net.BrowserChannel.notifyStatEvent(
2221
        goog.net.BrowserChannel.Stat.ERROR_NETWORK);
2222
    // We call onError_ here instead of signalError_ because the latter just
2223
    // calls notifyStatEvent, and we don't want to have another stat event.
2224
    this.onError_(goog.net.BrowserChannel.Error.NETWORK);
2225
  }
2226
};
2227

2228

2229
/**
2230
 * Called when messages have been successfully sent from the queue.
2231
 * @private
2232
 */
2233
goog.net.BrowserChannel.prototype.onSuccess_ = function() {
2234
  if (this.handler_) {
2235
    this.handler_.channelSuccess(this, this.pendingMaps_);
2236
  }
2237
};
2238

2239

2240
/**
2241
 * Called when we've determined the final error for a channel. It closes the
2242
 * notifiers the handler of the error and closes the channel.
2243
 * @param {goog.net.BrowserChannel.Error} error  The error code for the failure.
2244
 * @private
2245
 */
2246
goog.net.BrowserChannel.prototype.onError_ = function(error) {
2247
  this.channelDebug_.debug('HttpChannel: error - ' + error);
2248
  this.state_ = goog.net.BrowserChannel.State.CLOSED;
2249
  if (this.handler_) {
2250
    this.handler_.channelError(this, error);
2251
  }
2252
  this.onClose_();
2253
  this.cancelRequests_();
2254
};
2255

2256

2257
/**
2258
 * Called when the channel has been closed. It notifiers the handler of the
2259
 * event, and reports any pending or undelivered maps.
2260
 * @private
2261
 */
2262
goog.net.BrowserChannel.prototype.onClose_ = function() {
2263
  this.state_ = goog.net.BrowserChannel.State.CLOSED;
2264
  this.lastStatusCode_ = -1;
2265
  if (this.handler_) {
2266
    if (this.pendingMaps_.length == 0 && this.outgoingMaps_.length == 0) {
2267
      this.handler_.channelClosed(this);
2268
    } else {
2269
      this.channelDebug_.debug(
2270
          'Number of undelivered maps' +
2271
          ', pending: ' + this.pendingMaps_.length + ', outgoing: ' +
2272
          this.outgoingMaps_.length);
2273

2274
      var copyOfPendingMaps = goog.array.clone(this.pendingMaps_);
2275
      var copyOfUndeliveredMaps = goog.array.clone(this.outgoingMaps_);
2276
      this.pendingMaps_.length = 0;
2277
      this.outgoingMaps_.length = 0;
2278

2279
      this.handler_.channelClosed(
2280
          this, copyOfPendingMaps, copyOfUndeliveredMaps);
2281
    }
2282
  }
2283
};
2284

2285

2286
/**
2287
 * Gets the Uri used for the connection that sends data to the server.
2288
 * @param {string} path The path on the host.
2289
 * @return {!goog.Uri} The forward channel URI.
2290
 */
2291
goog.net.BrowserChannel.prototype.getForwardChannelUri = function(path) {
2292
  var uri = this.createDataUri(null, path);
2293
  this.channelDebug_.debug('GetForwardChannelUri: ' + uri);
2294
  return uri;
2295
};
2296

2297

2298
/**
2299
 * Gets the results for the first browser channel test
2300
 * @return {Array<string>} The results.
2301
 */
2302
goog.net.BrowserChannel.prototype.getFirstTestResults = function() {
2303
  return this.firstTestResults_;
2304
};
2305

2306

2307
/**
2308
 * Gets the results for the second browser channel test
2309
 * @return {?boolean} The results. True -> buffered connection,
2310
 *      False -> unbuffered, null -> unknown.
2311
 */
2312
goog.net.BrowserChannel.prototype.getSecondTestResults = function() {
2313
  return this.secondTestResults_;
2314
};
2315

2316

2317
/**
2318
 * Gets the Uri used for the connection that receives data from the server.
2319
 * @param {?string} hostPrefix The host prefix.
2320
 * @param {string} path The path on the host.
2321
 * @return {!goog.Uri} The back channel URI.
2322
 */
2323
goog.net.BrowserChannel.prototype.getBackChannelUri = function(
2324
    hostPrefix, path) {
2325
  var uri = this.createDataUri(
2326
      this.shouldUseSecondaryDomains() ? hostPrefix : null, path);
2327
  this.channelDebug_.debug('GetBackChannelUri: ' + uri);
2328
  return uri;
2329
};
2330

2331

2332
/**
2333
 * Creates a data Uri applying logic for secondary hostprefix, port
2334
 * overrides, and versioning.
2335
 * @param {?string} hostPrefix The host prefix.
2336
 * @param {string} path The path on the host (may be absolute or relative).
2337
 * @param {number=} opt_overridePort Optional override port.
2338
 * @return {!goog.Uri} The data URI.
2339
 */
2340
goog.net.BrowserChannel.prototype.createDataUri = function(
2341
    hostPrefix, path, opt_overridePort) {
2342
  var uri = goog.Uri.parse(path);
2343
  var uriAbsolute = (uri.getDomain() != '');
2344
  if (uriAbsolute) {
2345
    if (hostPrefix) {
2346
      uri.setDomain(hostPrefix + '.' + uri.getDomain());
2347
    }
2348

2349
    uri.setPort(opt_overridePort || uri.getPort());
2350
  } else {
2351
    var locationPage = window.location;
2352
    var hostName;
2353
    if (hostPrefix) {
2354
      hostName = hostPrefix + '.' + locationPage.hostname;
2355
    } else {
2356
      hostName = locationPage.hostname;
2357
    }
2358

2359
    var port = opt_overridePort || locationPage.port;
2360

2361
    uri = goog.Uri.create(locationPage.protocol, null, hostName, port, path);
2362
  }
2363

2364
  if (this.extraParams_) {
2365
    goog.object.forEach(this.extraParams_, function(value, key) {
2366
      uri.setParameterValue(key, value);
2367
    });
2368
  }
2369

2370
  // Add the protocol version to the URI.
2371
  uri.setParameterValue('VER', this.channelVersion_);
2372

2373
  // Add the reconnect parameters.
2374
  this.addAdditionalParams_(uri);
2375

2376
  return uri;
2377
};
2378

2379

2380
/**
2381
 * Called when BC needs to create an XhrIo object.  Override in a subclass if
2382
 * you need to customize the behavior, for example to enable the creation of
2383
 * XHR's capable of calling a secondary domain. Will also allow calling
2384
 * a secondary domain if withCredentials (CORS) is enabled.
2385
 * @param {?string} hostPrefix The host prefix, if we need an XhrIo object
2386
 *     capable of calling a secondary domain.
2387
 * @return {!goog.net.XhrIo} A new XhrIo object.
2388
 */
2389
goog.net.BrowserChannel.prototype.createXhrIo = function(hostPrefix) {
2390
  if (hostPrefix && !this.supportsCrossDomainXhrs_) {
2391
    throw Error('Can\'t create secondary domain capable XhrIo object.');
2392
  }
2393
  var xhr = new goog.net.XhrIo();
2394
  xhr.setWithCredentials(this.supportsCrossDomainXhrs_);
2395
  return xhr;
2396
};
2397

2398

2399
/**
2400
 * Gets whether this channel is currently active. This is used to determine the
2401
 * length of time to wait before retrying. This call delegates to the handler.
2402
 * @return {boolean} Whether the channel is currently active.
2403
 */
2404
goog.net.BrowserChannel.prototype.isActive = function() {
2405
  return !!this.handler_ && this.handler_.isActive(this);
2406
};
2407

2408

2409
/**
2410
 * Wrapper around SafeTimeout which calls the start and end execution hooks
2411
 * with a try...finally block.
2412
 * @param {Function} fn The callback function.
2413
 * @param {number} ms The time in MS for the timer.
2414
 * @return {number} The ID of the timer.
2415
 */
2416
goog.net.BrowserChannel.setTimeout = function(fn, ms) {
2417
  if (!goog.isFunction(fn)) {
2418
    throw Error('Fn must not be null and must be a function');
2419
  }
2420
  return goog.global.setTimeout(function() {
2421
    goog.net.BrowserChannel.onStartExecution();
2422
    try {
2423
      fn();
2424
    } finally {
2425
      goog.net.BrowserChannel.onEndExecution();
2426
    }
2427
  }, ms);
2428
};
2429

2430

2431
/**
2432
 * Helper function to call the start hook
2433
 */
2434
goog.net.BrowserChannel.onStartExecution = function() {
2435
  goog.net.BrowserChannel.startExecutionHook_();
2436
};
2437

2438

2439
/**
2440
 * Helper function to call the end hook
2441
 */
2442
goog.net.BrowserChannel.onEndExecution = function() {
2443
  goog.net.BrowserChannel.endExecutionHook_();
2444
};
2445

2446

2447
/**
2448
 * Returns the singleton event target for stat events.
2449
 * @return {goog.events.EventTarget} The event target for stat events.
2450
 */
2451
goog.net.BrowserChannel.getStatEventTarget = function() {
2452
  return goog.net.BrowserChannel.statEventTarget_;
2453
};
2454

2455

2456
/**
2457
 * Notify the channel that a particular fine grained network event has occurred.
2458
 * Should be considered package-private.
2459
 * @param {goog.net.BrowserChannel.ServerReachability} reachabilityType The
2460
 *     reachability event type.
2461
 */
2462
goog.net.BrowserChannel.prototype.notifyServerReachabilityEvent = function(
2463
    reachabilityType) {
2464
  var target = goog.net.BrowserChannel.statEventTarget_;
2465
  target.dispatchEvent(
2466
      new goog.net.BrowserChannel.ServerReachabilityEvent(
2467
          target, reachabilityType));
2468
};
2469

2470

2471
/**
2472
 * Helper function to call the stat event callback.
2473
 * @param {goog.net.BrowserChannel.Stat} stat The stat.
2474
 */
2475
goog.net.BrowserChannel.notifyStatEvent = function(stat) {
2476
  var target = goog.net.BrowserChannel.statEventTarget_;
2477
  target.dispatchEvent(new goog.net.BrowserChannel.StatEvent(target, stat));
2478
};
2479

2480

2481
/**
2482
 * Helper function to notify listeners about POST request performance.
2483
 *
2484
 * @param {number} size Number of characters in the POST data.
2485
 * @param {number} rtt The amount of time from POST start to response.
2486
 * @param {number} retries The number of times the POST had to be retried.
2487
 */
2488
goog.net.BrowserChannel.notifyTimingEvent = function(size, rtt, retries) {
2489
  var target = goog.net.BrowserChannel.statEventTarget_;
2490
  target.dispatchEvent(
2491
      new goog.net.BrowserChannel.TimingEvent(target, size, rtt, retries));
2492
};
2493

2494

2495
/**
2496
 * Determines whether to use a secondary domain when the server gives us
2497
 * a host prefix. This allows us to work around browser per-domain
2498
 * connection limits.
2499
 *
2500
 * Currently, we  use secondary domains when using Trident's ActiveXObject,
2501
 * because it supports cross-domain requests out of the box.  Note that in IE10
2502
 * we no longer use ActiveX since it's not supported in Metro mode and IE10
2503
 * supports XHR streaming.
2504
 *
2505
 * If you need to use secondary domains on other browsers and IE10,
2506
 * you have two choices:
2507
 *     1) If you only care about browsers that support CORS
2508
 *        (https://developer.mozilla.org/en-US/docs/HTTP_access_control), you
2509
 *        can use {@link #setSupportsCrossDomainXhrs} and set the appropriate
2510
 *        CORS response headers on the server.
2511
 *     2) Or, override this method in a subclass, and make sure that those
2512
 *        browsers use some messaging mechanism that works cross-domain (e.g
2513
 *        iframes and window.postMessage).
2514
 *
2515
 * @return {boolean} Whether to use secondary domains.
2516
 * @see http://code.google.com/p/closure-library/issues/detail?id=339
2517
 */
2518
goog.net.BrowserChannel.prototype.shouldUseSecondaryDomains = function() {
2519
  return this.supportsCrossDomainXhrs_ ||
2520
      !goog.net.ChannelRequest.supportsXhrStreaming();
2521
};
2522

2523

2524
/**
2525
 * A LogSaver that can be used to accumulate all the debug logs for
2526
 * BrowserChannels so they can be sent to the server when a problem is
2527
 * detected.
2528
 * @const
2529
 */
2530
goog.net.BrowserChannel.LogSaver = {};
2531

2532

2533
/**
2534
 * Buffer for accumulating the debug log
2535
 * @type {goog.structs.CircularBuffer}
2536
 * @private
2537
 */
2538
goog.net.BrowserChannel.LogSaver.buffer_ =
2539
    new goog.structs.CircularBuffer(1000);
2540

2541

2542
/**
2543
 * Whether we're currently accumulating the debug log.
2544
 * @type {boolean}
2545
 * @private
2546
 */
2547
goog.net.BrowserChannel.LogSaver.enabled_ = false;
2548

2549

2550
/**
2551
 * Formatter for saving logs.
2552
 * @type {goog.debug.Formatter}
2553
 * @private
2554
 */
2555
goog.net.BrowserChannel.LogSaver.formatter_ = new goog.debug.TextFormatter();
2556

2557

2558
/**
2559
 * Returns whether the LogSaver is enabled.
2560
 * @return {boolean} Whether saving is enabled or disabled.
2561
 */
2562
goog.net.BrowserChannel.LogSaver.isEnabled = function() {
2563
  return goog.net.BrowserChannel.LogSaver.enabled_;
2564
};
2565

2566

2567
/**
2568
 * Enables of disables the LogSaver.
2569
 * @param {boolean} enable Whether to enable or disable saving.
2570
 */
2571
goog.net.BrowserChannel.LogSaver.setEnabled = function(enable) {
2572
  if (enable == goog.net.BrowserChannel.LogSaver.enabled_) {
2573
    return;
2574
  }
2575

2576
  var fn = goog.net.BrowserChannel.LogSaver.addLogRecord;
2577
  var logger = goog.log.getLogger('goog.net');
2578
  if (enable) {
2579
    goog.log.addHandler(logger, fn);
2580
  } else {
2581
    goog.log.removeHandler(logger, fn);
2582
  }
2583
};
2584

2585

2586
/**
2587
 * Adds a log record.
2588
 * @param {goog.log.LogRecord} logRecord the LogRecord.
2589
 */
2590
goog.net.BrowserChannel.LogSaver.addLogRecord = function(logRecord) {
2591
  goog.net.BrowserChannel.LogSaver.buffer_.add(
2592
      goog.net.BrowserChannel.LogSaver.formatter_.formatRecord(logRecord));
2593
};
2594

2595

2596
/**
2597
 * Returns the log as a single string.
2598
 * @return {string} The log as a single string.
2599
 */
2600
goog.net.BrowserChannel.LogSaver.getBuffer = function() {
2601
  return goog.net.BrowserChannel.LogSaver.buffer_.getValues().join('');
2602
};
2603

2604

2605
/**
2606
 * Clears the buffer
2607
 */
2608
goog.net.BrowserChannel.LogSaver.clearBuffer = function() {
2609
  goog.net.BrowserChannel.LogSaver.buffer_.clear();
2610
};
2611

2612

2613

2614
/**
2615
 * Abstract base class for the browser channel handler
2616
 * @constructor
2617
 */
2618
goog.net.BrowserChannel.Handler = function() {};
2619

2620

2621
/**
2622
 * Callback handler for when a batch of response arrays is received from the
2623
 * server.
2624
 * @type {?function(!goog.net.BrowserChannel, !Array<!Array<?>>)}
2625
 */
2626
goog.net.BrowserChannel.Handler.prototype.channelHandleMultipleArrays = null;
2627

2628

2629
/**
2630
 * Whether it's okay to make a request to the server. A handler can return
2631
 * false if the channel should fail. For example, if the user has logged out,
2632
 * the handler may want all requests to fail immediately.
2633
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2634
 * @return {goog.net.BrowserChannel.Error} An error code. The code should
2635
 * return goog.net.BrowserChannel.Error.OK to indicate it's okay. Any other
2636
 * error code will cause a failure.
2637
 */
2638
goog.net.BrowserChannel.Handler.prototype.okToMakeRequest = function(
2639
    browserChannel) {
2640
  return goog.net.BrowserChannel.Error.OK;
2641
};
2642

2643

2644
/**
2645
 * Indicates the BrowserChannel has successfully negotiated with the server
2646
 * and can now send and receive data.
2647
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2648
 */
2649
goog.net.BrowserChannel.Handler.prototype.channelOpened = function(
2650
    browserChannel) {};
2651

2652

2653
/**
2654
 * New input is available for the application to process.
2655
 *
2656
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2657
 * @param {Array<?>} array The data array.
2658
 */
2659
goog.net.BrowserChannel.Handler.prototype.channelHandleArray = function(
2660
    browserChannel, array) {};
2661

2662

2663
/**
2664
 * Indicates maps were successfully sent on the BrowserChannel.
2665
 *
2666
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2667
 * @param {Array<goog.net.BrowserChannel.QueuedMap>} deliveredMaps The
2668
 *     array of maps that have been delivered to the server. This is a direct
2669
 *     reference to the internal BrowserChannel array, so a copy should be made
2670
 *     if the caller desires a reference to the data.
2671
 */
2672
goog.net.BrowserChannel.Handler.prototype.channelSuccess = function(
2673
    browserChannel, deliveredMaps) {};
2674

2675

2676
/**
2677
 * Indicates an error occurred on the BrowserChannel.
2678
 *
2679
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2680
 * @param {goog.net.BrowserChannel.Error} error The error code.
2681
 */
2682
goog.net.BrowserChannel.Handler.prototype.channelError = function(
2683
    browserChannel, error) {};
2684

2685

2686
/**
2687
 * Indicates the BrowserChannel is closed. Also notifies about which maps,
2688
 * if any, that may not have been delivered to the server.
2689
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2690
 * @param {Array<goog.net.BrowserChannel.QueuedMap>=} opt_pendingMaps The
2691
 *     array of pending maps, which may or may not have been delivered to the
2692
 *     server.
2693
 * @param {Array<goog.net.BrowserChannel.QueuedMap>=} opt_undeliveredMaps
2694
 *     The array of undelivered maps, which have definitely not been delivered
2695
 *     to the server.
2696
 */
2697
goog.net.BrowserChannel.Handler.prototype.channelClosed = function(
2698
    browserChannel, opt_pendingMaps, opt_undeliveredMaps) {};
2699

2700

2701
/**
2702
 * Gets any parameters that should be added at the time another connection is
2703
 * made to the server.
2704
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2705
 * @return {!Object} Extra parameter keys and values to add to the
2706
 *     requests.
2707
 */
2708
goog.net.BrowserChannel.Handler.prototype.getAdditionalParams = function(
2709
    browserChannel) {
2710
  return {};
2711
};
2712

2713

2714
/**
2715
 * Gets the URI of an image that can be used to test network connectivity.
2716
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2717
 * @return {goog.Uri?} A custom URI to load for the network test.
2718
 */
2719
goog.net.BrowserChannel.Handler.prototype.getNetworkTestImageUri = function(
2720
    browserChannel) {
2721
  return null;
2722
};
2723

2724

2725
/**
2726
 * Gets whether this channel is currently active. This is used to determine the
2727
 * length of time to wait before retrying.
2728
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2729
 * @return {boolean} Whether the channel is currently active.
2730
 */
2731
goog.net.BrowserChannel.Handler.prototype.isActive = function(browserChannel) {
2732
  return true;
2733
};
2734

2735

2736
/**
2737
 * Called by the channel if enumeration of the map throws an exception.
2738
 * @param {goog.net.BrowserChannel} browserChannel The browser channel.
2739
 * @param {Object} map The map that can't be enumerated.
2740
 */
2741
goog.net.BrowserChannel.Handler.prototype.badMapError = function(
2742
    browserChannel, map) {
2743
  return;
2744
};
2745

2746

2747
/**
2748
 * Allows the handler to override a host prefix provided by the server.  Will
2749
 * be called whenever the channel has received such a prefix and is considering
2750
 * its use.
2751
 * @param {?string} serverHostPrefix The host prefix provided by the server.
2752
 * @return {?string} The host prefix the client should use.
2753
 */
2754
goog.net.BrowserChannel.Handler.prototype.correctHostPrefix = function(
2755
    serverHostPrefix) {
2756
  return serverHostPrefix;
2757
};
2758

2759