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// Copyright 2007 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 Contains the iframe polling transport.
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 */
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goog.provide('goog.net.xpc.IframePollingTransport');
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goog.provide('goog.net.xpc.IframePollingTransport.Receiver');
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goog.provide('goog.net.xpc.IframePollingTransport.Sender');
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goog.require('goog.array');
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goog.require('goog.dom');
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goog.require('goog.dom.TagName');
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goog.require('goog.log');
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goog.require('goog.log.Level');
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goog.require('goog.net.xpc');
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goog.require('goog.net.xpc.CfgFields');
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goog.require('goog.net.xpc.CrossPageChannelRole');
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goog.require('goog.net.xpc.Transport');
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goog.require('goog.net.xpc.TransportTypes');
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goog.require('goog.userAgent');
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37

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/**
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 * Iframe polling transport. Uses hidden iframes to transfer data
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 * in the fragment identifier of the URL. The peer polls the iframe's location
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 * for changes.
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 * Unfortunately, in Safari this screws up the history, because Safari doesn't
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 * allow to call location.replace() on a window containing a document from a
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 * different domain (last version tested: 2.0.4).
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 *
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 * @param {goog.net.xpc.CrossPageChannel} channel The channel this
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 *     transport belongs to.
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 * @param {goog.dom.DomHelper=} opt_domHelper The dom helper to use for finding
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 *     the correct window.
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 * @constructor
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 * @extends {goog.net.xpc.Transport}
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 * @final
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 */
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goog.net.xpc.IframePollingTransport = function(channel, opt_domHelper) {
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  goog.net.xpc.IframePollingTransport.base(this, 'constructor', opt_domHelper);
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  /**
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   * The channel this transport belongs to.
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   * @type {goog.net.xpc.CrossPageChannel}
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   * @private
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   */
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  this.channel_ = channel;
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  /**
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   * The URI used to send messages.
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   * @type {string}
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   * @private
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   */
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  this.sendUri_ =
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      this.channel_.getConfig()[goog.net.xpc.CfgFields.PEER_POLL_URI];
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  /**
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   * The URI which is polled for incoming messages.
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   * @type {string}
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   * @private
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   */
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  this.rcvUri_ =
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      this.channel_.getConfig()[goog.net.xpc.CfgFields.LOCAL_POLL_URI];
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  /**
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   * The queue to hold messages which can't be sent immediately.
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   * @type {Array<string>}
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   * @private
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   */
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  this.sendQueue_ = [];
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};
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goog.inherits(goog.net.xpc.IframePollingTransport, goog.net.xpc.Transport);
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/**
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 * The number of times the inner frame will check for evidence of the outer
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 * frame before it tries its reconnection sequence.  These occur at 100ms
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 * intervals, making this an effective max waiting period of 500ms.
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 * @type {number}
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.pollsBeforeReconnect_ = 5;
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/**
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 * The transport type.
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 * @type {number}
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 * @protected
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 * @override
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 */
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goog.net.xpc.IframePollingTransport.prototype.transportType =
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    goog.net.xpc.TransportTypes.IFRAME_POLLING;
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/**
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 * Sequence counter.
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 * @type {number}
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.sequence_ = 0;
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/**
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 * Flag indicating whether we are waiting for an acknoledgement.
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 * @type {boolean}
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.waitForAck_ = false;
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/**
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 * Flag indicating if channel has been initialized.
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 * @type {boolean}
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.initialized_ = false;
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/**
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 * Reconnection iframe created by inner peer.
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 * @type {Element}
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.reconnectFrame_ = null;
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/** @private {goog.net.xpc.IframePollingTransport.Receiver} */
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goog.net.xpc.IframePollingTransport.prototype.ackReceiver_;
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/** @private {goog.net.xpc.IframePollingTransport.Sender} */
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goog.net.xpc.IframePollingTransport.prototype.ackSender_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.ackIframeElm_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.ackWinObj_;
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/** @private {!Function|undefined} */
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goog.net.xpc.IframePollingTransport.prototype.checkLocalFramesPresentCb_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.deliveryQueue_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.msgIframeElm_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.msgReceiver_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.msgSender_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.msgWinObj_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.rcvdConnectionSetupAck_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.sentConnectionSetupAck_;
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/** @private */
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goog.net.xpc.IframePollingTransport.prototype.parts_;
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/**
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 * The string used to prefix all iframe names and IDs.
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 * @type {string}
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 */
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goog.net.xpc.IframePollingTransport.IFRAME_PREFIX = 'googlexpc';
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/**
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 * Returns the name/ID of the message frame.
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 * @return {string} Name of message frame.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.getMsgFrameName_ = function() {
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  return goog.net.xpc.IframePollingTransport.IFRAME_PREFIX + '_' +
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      this.channel_.name + '_msg';
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};
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/**
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 * Returns the name/ID of the ack frame.
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 * @return {string} Name of ack frame.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.getAckFrameName_ = function() {
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  return goog.net.xpc.IframePollingTransport.IFRAME_PREFIX + '_' +
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      this.channel_.name + '_ack';
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};
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/**
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 * Determines whether the channel is still available. The channel is
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 * unavailable if the transport was disposed or the peer is no longer
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 * available.
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 * @return {boolean} Whether the channel is available.
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 */
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goog.net.xpc.IframePollingTransport.prototype.isChannelAvailable = function() {
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  return !this.isDisposed() && this.channel_.isPeerAvailable();
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};
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/**
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 * Safely retrieves the frames from the peer window. If an error is thrown
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 * (e.g. the window is closing) an empty frame object is returned.
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 * @return {!Object<string|number, !Window>} The frames from the peer window.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.getPeerFrames_ = function() {
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  try {
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    if (this.isChannelAvailable()) {
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      return this.channel_.getPeerWindowObject().frames || {};
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    }
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  } catch (e) {
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    // An error may be thrown if the window is closing.
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    goog.log.fine(goog.net.xpc.logger, 'error retrieving peer frames');
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  }
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  return {};
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};
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/**
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 * Safely retrieves the peer frame with the specified name.
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 * @param {string} frameName The name of the peer frame to retrieve.
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 * @return {!Window} The peer frame with the specified name.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.getPeerFrame_ = function(
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    frameName) {
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  return this.getPeerFrames_()[frameName];
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};
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/**
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 * Connects this transport.
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 * @override
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 */
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goog.net.xpc.IframePollingTransport.prototype.connect = function() {
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  if (!this.isChannelAvailable()) {
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    // When the channel is unavailable there is no peer to poll so stop trying
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    // to connect.
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    return;
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  }
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  goog.log.fine(goog.net.xpc.logger, 'transport connect called');
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  if (!this.initialized_) {
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    goog.log.fine(goog.net.xpc.logger, 'initializing...');
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    this.constructSenderFrames_();
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    this.initialized_ = true;
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  }
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  this.checkForeignFramesReady_();
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};
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/**
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 * Creates the iframes which are used to send messages (and acknowledgements)
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 * to the peer. Sender iframes contain a document from a different origin and
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 * therefore their content can't be accessed.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.constructSenderFrames_ =
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    function() {
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  var name = this.getMsgFrameName_();
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  this.msgIframeElm_ = this.constructSenderFrame_(name);
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  this.msgWinObj_ = this.getWindow().frames[name];
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  name = this.getAckFrameName_();
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  this.ackIframeElm_ = this.constructSenderFrame_(name);
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  this.ackWinObj_ = this.getWindow().frames[name];
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};
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/**
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 * Constructs a sending frame the the given id.
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 * @param {string} id The id.
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 * @return {!Element} The constructed frame.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.constructSenderFrame_ = function(
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    id) {
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  goog.log.log(
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      goog.net.xpc.logger, goog.log.Level.FINEST,
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      'constructing sender frame: ' + id);
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  var ifr = goog.dom.createElement(goog.dom.TagName.IFRAME);
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  var s = ifr.style;
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  s.position = 'absolute';
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  s.top = '-10px';
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  s.left = '10px';
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  s.width = '1px';
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  s.height = '1px';
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  ifr.id = ifr.name = id;
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  ifr.src = this.sendUri_ + '#INITIAL';
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  this.getWindow().document.body.appendChild(ifr);
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  return ifr;
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};
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328

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/**
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 * The protocol for reconnecting is for the inner frame to change channel
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 * names, and then communicate the new channel name to the outer peer.
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 * The outer peer looks in a predefined location for the channel name
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 * upate. It is important to use a completely new channel name, as this
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 * will ensure that all messaging iframes are not in the bfcache.
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 * Otherwise, Safari may pollute the history when modifying the location
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 * of bfcached iframes.
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 * @private
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 */
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goog.net.xpc.IframePollingTransport.prototype.maybeInnerPeerReconnect_ =
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    function() {
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  // Reconnection has been found to not function on some browsers (eg IE7), so
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  // it's important that the mechanism only be triggered as a last resort.  As
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  // such, we poll a number of times to find the outer iframe before triggering
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  // it.
345
  if (this.reconnectFrame_ || this.pollsBeforeReconnect_-- > 0) {
346
    return;
347
  }
348

349
  goog.log.log(
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      goog.net.xpc.logger, goog.log.Level.FINEST,
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      'Inner peer reconnect triggered.');
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  this.channel_.updateChannelNameAndCatalog(goog.net.xpc.getRandomString(10));
353
  goog.log.log(
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      goog.net.xpc.logger, goog.log.Level.FINEST,
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      'switching channels: ' + this.channel_.name);
356
  this.deconstructSenderFrames_();
357
  this.initialized_ = false;
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  // Communicate new channel name to outer peer.
359
  this.reconnectFrame_ = this.constructSenderFrame_(
360
      goog.net.xpc.IframePollingTransport.IFRAME_PREFIX + '_reconnect_' +
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      this.channel_.name);
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};
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364

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/**
366
 * Scans inner peer for a reconnect message, which will be used to update
367
 * the outer peer's channel name. If a reconnect message is found, the
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 * sender frames will be cleaned up to make way for the new sender frames.
369
 * Only called by the outer peer.
370
 * @private
371
 */
372
goog.net.xpc.IframePollingTransport.prototype.outerPeerReconnect_ = function() {
373
  goog.log.log(
374
      goog.net.xpc.logger, goog.log.Level.FINEST, 'outerPeerReconnect called');
375
  var frames = this.getPeerFrames_();
376
  var length = frames.length;
377
  for (var i = 0; i < length; i++) {
378
    var frameName;
379
    try {
380
      if (frames[i] && frames[i].name) {
381
        frameName = frames[i].name;
382
      }
383
    } catch (e) {
384
      // Do nothing.
385
    }
386
    if (!frameName) {
387
      continue;
388
    }
389
    var message = frameName.split('_');
390
    if (message.length == 3 &&
391
        message[0] == goog.net.xpc.IframePollingTransport.IFRAME_PREFIX &&
392
        message[1] == 'reconnect') {
393
      // This is a legitimate reconnect message from the peer. Start using
394
      // the peer provided channel name, and start a connection over from
395
      // scratch.
396
      this.channel_.name = message[2];
397
      this.deconstructSenderFrames_();
398
      this.initialized_ = false;
399
      break;
400
    }
401
  }
402
};
403

404

405
/**
406
 * Cleans up the existing sender frames owned by this peer. Only called by
407
 * the outer peer.
408
 * @private
409
 */
410
goog.net.xpc.IframePollingTransport.prototype.deconstructSenderFrames_ =
411
    function() {
412
  goog.log.log(
413
      goog.net.xpc.logger, goog.log.Level.FINEST,
414
      'deconstructSenderFrames called');
415
  if (this.msgIframeElm_) {
416
    this.msgIframeElm_.parentNode.removeChild(this.msgIframeElm_);
417
    this.msgIframeElm_ = null;
418
    this.msgWinObj_ = null;
419
  }
420
  if (this.ackIframeElm_) {
421
    this.ackIframeElm_.parentNode.removeChild(this.ackIframeElm_);
422
    this.ackIframeElm_ = null;
423
    this.ackWinObj_ = null;
424
  }
425
};
426

427

428
/**
429
 * Checks if the frames in the peer's page are ready. These contain a
430
 * document from the own domain and are the ones messages are received through.
431
 * @private
432
 */
433
goog.net.xpc.IframePollingTransport.prototype.checkForeignFramesReady_ =
434
    function() {
435
  // check if the connected iframe ready
436
  if (!(this.isRcvFrameReady_(this.getMsgFrameName_()) &&
437
        this.isRcvFrameReady_(this.getAckFrameName_()))) {
438
    goog.log.log(
439
        goog.net.xpc.logger, goog.log.Level.FINEST,
440
        'foreign frames not (yet) present');
441

442
    if (this.channel_.getRole() == goog.net.xpc.CrossPageChannelRole.INNER) {
443
      // The outer peer might need a short time to get its frames ready, as
444
      // CrossPageChannel prevents them from getting created until the inner
445
      // peer's frame has thrown its loaded event.  This method is a noop for
446
      // the first few times it's called, and then allows the reconnection
447
      // sequence to begin.
448
      this.maybeInnerPeerReconnect_();
449
    } else if (
450
        this.channel_.getRole() == goog.net.xpc.CrossPageChannelRole.OUTER) {
451
      // The inner peer is either not loaded yet, or the receiving
452
      // frames are simply missing. Since we cannot discern the two cases, we
453
      // should scan for a reconnect message from the inner peer.
454
      this.outerPeerReconnect_();
455
    }
456

457
    // start a timer to check again
458
    this.getWindow().setTimeout(goog.bind(this.connect, this), 100);
459
  } else {
460
    goog.log.fine(goog.net.xpc.logger, 'foreign frames present');
461

462
    // Create receivers.
463
    this.msgReceiver_ = new goog.net.xpc.IframePollingTransport.Receiver(
464
        this, this.getPeerFrame_(this.getMsgFrameName_()),
465
        goog.bind(this.processIncomingMsg, this));
466
    this.ackReceiver_ = new goog.net.xpc.IframePollingTransport.Receiver(
467
        this, this.getPeerFrame_(this.getAckFrameName_()),
468
        goog.bind(this.processIncomingAck, this));
469

470
    this.checkLocalFramesPresent_();
471
  }
472
};
473

474

475
/**
476
 * Checks if the receiving frame is ready.
477
 * @param {string} frameName Which receiving frame to check.
478
 * @return {boolean} Whether the receiving frame is ready.
479
 * @private
480
 */
481
goog.net.xpc.IframePollingTransport.prototype.isRcvFrameReady_ = function(
482
    frameName) {
483
  goog.log.log(
484
      goog.net.xpc.logger, goog.log.Level.FINEST,
485
      'checking for receive frame: ' + frameName);
486

487
  try {
488
    var winObj = this.getPeerFrame_(frameName);
489
    if (!winObj || winObj.location.href.indexOf(this.rcvUri_) != 0) {
490
      return false;
491
    }
492
  } catch (e) {
493
    return false;
494
  }
495
  return true;
496
};
497

498

499
/**
500
 * Checks if the iframes created in the own document are ready.
501
 * @private
502
 */
503
goog.net.xpc.IframePollingTransport.prototype.checkLocalFramesPresent_ =
504
    function() {
505

506
  // Are the sender frames ready?
507
  // These contain a document from the peer's domain, therefore we can only
508
  // check if the frame itself is present.
509
  var frames = this.getPeerFrames_();
510
  if (!(frames[this.getAckFrameName_()] && frames[this.getMsgFrameName_()])) {
511
    // start a timer to check again
512
    if (!this.checkLocalFramesPresentCb_) {
513
      this.checkLocalFramesPresentCb_ =
514
          goog.bind(this.checkLocalFramesPresent_, this);
515
    }
516
    this.getWindow().setTimeout(this.checkLocalFramesPresentCb_, 100);
517
    goog.log.fine(goog.net.xpc.logger, 'local frames not (yet) present');
518
  } else {
519
    // Create senders.
520
    this.msgSender_ = new goog.net.xpc.IframePollingTransport.Sender(
521
        this.sendUri_, this.msgWinObj_);
522
    this.ackSender_ = new goog.net.xpc.IframePollingTransport.Sender(
523
        this.sendUri_, this.ackWinObj_);
524

525
    goog.log.fine(goog.net.xpc.logger, 'local frames ready');
526

527
    this.getWindow().setTimeout(goog.bind(function() {
528
      this.msgSender_.send(goog.net.xpc.SETUP);
529
      this.waitForAck_ = true;
530
      goog.log.fine(goog.net.xpc.logger, 'SETUP sent');
531
    }, this), 100);
532
  }
533
};
534

535

536
/**
537
 * Check if connection is ready.
538
 * @private
539
 */
540
goog.net.xpc.IframePollingTransport.prototype.checkIfConnected_ = function() {
541
  if (this.sentConnectionSetupAck_ && this.rcvdConnectionSetupAck_) {
542
    this.channel_.notifyConnected();
543

544
    if (this.deliveryQueue_) {
545
      goog.log.fine(
546
          goog.net.xpc.logger, 'delivering queued messages ' +
547
              '(' + this.deliveryQueue_.length + ')');
548

549
      for (var i = 0, m; i < this.deliveryQueue_.length; i++) {
550
        m = this.deliveryQueue_[i];
551
        this.channel_.xpcDeliver(m.service, m.payload);
552
      }
553
      delete this.deliveryQueue_;
554
    }
555
  } else {
556
    goog.log.log(
557
        goog.net.xpc.logger, goog.log.Level.FINEST, 'checking if connected: ' +
558
            'ack sent:' + this.sentConnectionSetupAck_ + ', ack rcvd: ' +
559
            this.rcvdConnectionSetupAck_);
560
  }
561
};
562

563

564
/**
565
 * Processes an incoming message.
566
 * @param {string} raw The complete received string.
567
 */
568
goog.net.xpc.IframePollingTransport.prototype.processIncomingMsg = function(
569
    raw) {
570
  goog.log.log(
571
      goog.net.xpc.logger, goog.log.Level.FINEST, 'msg received: ' + raw);
572

573
  if (raw == goog.net.xpc.SETUP) {
574
    if (!this.ackSender_) {
575
      // Got SETUP msg, but we can't send an ack.
576
      return;
577
    }
578

579
    this.ackSender_.send(goog.net.xpc.SETUP_ACK_);
580
    goog.log.log(goog.net.xpc.logger, goog.log.Level.FINEST, 'SETUP_ACK sent');
581

582
    this.sentConnectionSetupAck_ = true;
583
    this.checkIfConnected_();
584

585
  } else if (this.channel_.isConnected() || this.sentConnectionSetupAck_) {
586
    var pos = raw.indexOf('|');
587
    var head = raw.substring(0, pos);
588
    var frame = raw.substring(pos + 1);
589

590
    // check if it is a framed message
591
    pos = head.indexOf(',');
592
    if (pos == -1) {
593
      var seq = head;
594
      // send acknowledgement
595
      this.ackSender_.send('ACK:' + seq);
596
      this.deliverPayload_(frame);
597
    } else {
598
      var seq = head.substring(0, pos);
599
      // send acknowledgement
600
      this.ackSender_.send('ACK:' + seq);
601

602
      var partInfo = head.substring(pos + 1).split('/');
603
      var part0 = parseInt(partInfo[0], 10);
604
      var part1 = parseInt(partInfo[1], 10);
605
      // create an array to accumulate the parts if this is the
606
      // first frame of a message
607
      if (part0 == 1) {
608
        this.parts_ = [];
609
      }
610
      this.parts_.push(frame);
611
      // deliver the message if this was the last frame of a message
612
      if (part0 == part1) {
613
        this.deliverPayload_(this.parts_.join(''));
614
        delete this.parts_;
615
      }
616
    }
617
  } else {
618
    goog.log.warning(
619
        goog.net.xpc.logger, 'received msg, but channel is not connected');
620
  }
621
};
622

623

624
/**
625
 * Process an incoming acknowdedgement.
626
 * @param {string} msgStr The incoming ack string to process.
627
 */
628
goog.net.xpc.IframePollingTransport.prototype.processIncomingAck = function(
629
    msgStr) {
630
  goog.log.log(
631
      goog.net.xpc.logger, goog.log.Level.FINEST, 'ack received: ' + msgStr);
632

633
  if (msgStr == goog.net.xpc.SETUP_ACK_) {
634
    this.waitForAck_ = false;
635
    this.rcvdConnectionSetupAck_ = true;
636
    // send the next frame
637
    this.checkIfConnected_();
638

639
  } else if (this.channel_.isConnected()) {
640
    if (!this.waitForAck_) {
641
      goog.log.warning(goog.net.xpc.logger, 'got unexpected ack');
642
      return;
643
    }
644

645
    var seq = parseInt(msgStr.split(':')[1], 10);
646
    if (seq == this.sequence_) {
647
      this.waitForAck_ = false;
648
      this.sendNextFrame_();
649
    } else {
650
      goog.log.warning(goog.net.xpc.logger, 'got ack with wrong sequence');
651
    }
652
  } else {
653
    goog.log.warning(
654
        goog.net.xpc.logger, 'received ack, but channel not connected');
655
  }
656
};
657

658

659
/**
660
 * Sends a frame (message part).
661
 * @private
662
 */
663
goog.net.xpc.IframePollingTransport.prototype.sendNextFrame_ = function() {
664
  // do nothing if we are waiting for an acknowledgement or the
665
  // queue is emtpy
666
  if (this.waitForAck_ || !this.sendQueue_.length) {
667
    return;
668
  }
669

670
  var s = this.sendQueue_.shift();
671
  ++this.sequence_;
672
  this.msgSender_.send(this.sequence_ + s);
673
  goog.log.log(
674
      goog.net.xpc.logger, goog.log.Level.FINEST,
675
      'msg sent: ' + this.sequence_ + s);
676

677

678
  this.waitForAck_ = true;
679
};
680

681

682
/**
683
 * Delivers a message.
684
 * @param {string} s The complete message string ("<service_name>:<payload>").
685
 * @private
686
 */
687
goog.net.xpc.IframePollingTransport.prototype.deliverPayload_ = function(s) {
688
  // determine the service name and the payload
689
  var pos = s.indexOf(':');
690
  var service = s.substr(0, pos);
691
  var payload = s.substring(pos + 1);
692

693
  // deliver the message
694
  if (!this.channel_.isConnected()) {
695
    // as valid messages can come in before a SETUP_ACK has
696
    // been received (because subchannels for msgs and acks are independent),
697
    // delay delivery of early messages until after 'connect'-event
698
    (this.deliveryQueue_ || (this.deliveryQueue_ = [
699
     ])).push({service: service, payload: payload});
700
    goog.log.log(goog.net.xpc.logger, goog.log.Level.FINEST, 'queued delivery');
701
  } else {
702
    this.channel_.xpcDeliver(service, payload);
703
  }
704
};
705

706

707
// ---- send message ----
708

709

710
/**
711
 * Maximal frame length.
712
 * @type {number}
713
 * @private
714
 */
715
goog.net.xpc.IframePollingTransport.prototype.MAX_FRAME_LENGTH_ = 3800;
716

717

718
/**
719
 * Sends a message. Splits it in multiple frames if too long (exceeds IE's
720
 * URL-length maximum.
721
 * Wireformat: `<seq>[,<frame_no>/<#frames>]|<frame_content>`
722
 *
723
 * @param {string} service Name of service this the message has to be delivered.
724
 * @param {string} payload The message content.
725
 * @override
726
 */
727
goog.net.xpc.IframePollingTransport.prototype.send = function(
728
    service, payload) {
729
  var frame = service + ':' + payload;
730
  // put in queue
731
  if (!goog.userAgent.IE || payload.length <= this.MAX_FRAME_LENGTH_) {
732
    this.sendQueue_.push('|' + frame);
733
  } else {
734
    var l = payload.length;
735
    var num = Math.ceil(l / this.MAX_FRAME_LENGTH_);  // number of frames
736
    var pos = 0;
737
    var i = 1;
738
    while (pos < l) {
739
      this.sendQueue_.push(
740
          ',' + i + '/' + num + '|' +
741
          frame.substr(pos, this.MAX_FRAME_LENGTH_));
742
      i++;
743
      pos += this.MAX_FRAME_LENGTH_;
744
    }
745
  }
746
  this.sendNextFrame_();
747
};
748

749

750
/** @override */
751
goog.net.xpc.IframePollingTransport.prototype.disposeInternal = function() {
752
  goog.net.xpc.IframePollingTransport.base(this, 'disposeInternal');
753

754
  var receivers = goog.net.xpc.IframePollingTransport.receivers_;
755
  goog.array.remove(receivers, this.msgReceiver_);
756
  goog.array.remove(receivers, this.ackReceiver_);
757
  this.msgReceiver_ = this.ackReceiver_ = null;
758

759
  goog.dom.removeNode(this.msgIframeElm_);
760
  goog.dom.removeNode(this.ackIframeElm_);
761
  this.msgIframeElm_ = this.ackIframeElm_ = null;
762
  this.msgWinObj_ = this.ackWinObj_ = null;
763
};
764

765

766
/**
767
 * Array holding all Receiver-instances.
768
 * @type {Array<goog.net.xpc.IframePollingTransport.Receiver>}
769
 * @private
770
 */
771
goog.net.xpc.IframePollingTransport.receivers_ = [];
772

773

774
/**
775
 * Short polling interval.
776
 * @type {number}
777
 * @private
778
 */
779
goog.net.xpc.IframePollingTransport.TIME_POLL_SHORT_ = 10;
780

781

782
/**
783
 * Long polling interval.
784
 * @type {number}
785
 * @private
786
 */
787
goog.net.xpc.IframePollingTransport.TIME_POLL_LONG_ = 100;
788

789

790
/**
791
 * Period how long to use TIME_POLL_SHORT_ before raising polling-interval
792
 * to TIME_POLL_LONG_ after an activity.
793
 * @type {number}
794
 * @private
795
 */
796
goog.net.xpc.IframePollingTransport.TIME_SHORT_POLL_AFTER_ACTIVITY_ = 1000;
797

798

799
/**
800
 * Polls all receivers.
801
 * @private
802
 */
803
goog.net.xpc.IframePollingTransport.receive_ = function() {
804
  var receivers = goog.net.xpc.IframePollingTransport.receivers_;
805
  var receiver;
806
  var rcvd = false;
807

808

809
  try {
810
    for (var i = 0; receiver = receivers[i]; i++) {
811
      rcvd = rcvd || receiver.receive();
812
    }
813
  } catch (e) {
814
    goog.log.info(goog.net.xpc.logger, 'receive_() failed: ' + e);
815

816
    // Notify the channel that the transport had an error.
817
    receiver.transport_.channel_.notifyTransportError();
818

819
    // notifyTransportError() closes the channel and disposes the transport.
820
    // If there are no other channels present, this.receivers_ will now be empty
821
    // and there is no need to keep polling.
822
    if (!receivers.length) {
823
      return;
824
    }
825
  }
826

827
  var now = goog.now();
828
  if (rcvd) {
829
    goog.net.xpc.IframePollingTransport.lastActivity_ = now;
830
  }
831

832
  // Schedule next check.
833
  var t = now - goog.net.xpc.IframePollingTransport.lastActivity_ <
834
          goog.net.xpc.IframePollingTransport.TIME_SHORT_POLL_AFTER_ACTIVITY_ ?
835
      goog.net.xpc.IframePollingTransport.TIME_POLL_SHORT_ :
836
      goog.net.xpc.IframePollingTransport.TIME_POLL_LONG_;
837
  goog.net.xpc.IframePollingTransport.rcvTimer_ =
838
      window.setTimeout(goog.net.xpc.IframePollingTransport.receiveCb_, t);
839
};
840

841

842
/**
843
 * Callback that wraps receive_ to be used in timers.
844
 * @type {Function}
845
 * @private
846
 */
847
goog.net.xpc.IframePollingTransport.receiveCb_ = goog.bind(
848
    goog.net.xpc.IframePollingTransport.receive_,
849
    goog.net.xpc.IframePollingTransport);
850

851

852
/**
853
 * Starts the polling loop.
854
 * @private
855
 */
856
goog.net.xpc.IframePollingTransport.startRcvTimer_ = function() {
857
  goog.log.fine(goog.net.xpc.logger, 'starting receive-timer');
858
  goog.net.xpc.IframePollingTransport.lastActivity_ = goog.now();
859
  if (goog.net.xpc.IframePollingTransport.rcvTimer_) {
860
    window.clearTimeout(goog.net.xpc.IframePollingTransport.rcvTimer_);
861
  }
862
  goog.net.xpc.IframePollingTransport.rcvTimer_ = window.setTimeout(
863
      goog.net.xpc.IframePollingTransport.receiveCb_,
864
      goog.net.xpc.IframePollingTransport.TIME_POLL_SHORT_);
865
};
866

867

868

869
/**
870
 * goog.net.xpc.IframePollingTransport.Sender
871
 *
872
 * Utility class to send message-parts to a document from a different origin.
873
 *
874
 * @constructor
875
 * @param {string} url The url the other document will use for polling. Must
876
 *     be an http:// or https:// URL.
877
 * @param {Object} windowObj The frame used for sending information to.
878
 * @final
879
 */
880
goog.net.xpc.IframePollingTransport.Sender = function(url, windowObj) {
881
  // This class is instantiated from goog.net.xpc.IframePollingTransport, which
882
  // takes its URLs from a goog.net.xpc.CrossPageChannel, which in turns
883
  // sanitizes them. However, since this class can be instantiated from
884
  // elsewhere than IframePollingTransport the url needs to be sanitized
885
  // here too.
886
  if (!/^https?:\/\//.test(url)) {
887
    throw Error('URL ' + url + ' is invalid');
888
  }
889

890
  /**
891
   * The URI used to sending messages.
892
   * @type {string}
893
   * @private
894
   */
895
  this.sanitizedSendUri_ = url;
896

897
  /**
898
   * The window object of the iframe used to send messages.
899
   * The script instantiating the Sender won't have access to
900
   * the content of sendFrame_.
901
   * @type {Window}
902
   * @private
903
   */
904
  this.sendFrame_ = /** @type {Window} */ (windowObj);
905

906
  /**
907
   * Cycle counter (used to make sure that sending two identical messages sent
908
   * in direct succession can be recognized as such by the receiver).
909
   * @type {number}
910
   * @private
911
   */
912
  this.cycle_ = 0;
913
};
914

915

916
/**
917
 * Sends a message-part (frame) to the peer.
918
 * The message-part is encoded and put in the fragment identifier
919
 * of the URL used for sending (and belongs to the origin/domain of the peer).
920
 * @param {string} payload The message to send.
921
 */
922
goog.net.xpc.IframePollingTransport.Sender.prototype.send = function(payload) {
923
  this.cycle_ = ++this.cycle_ % 2;
924

925
  var url =
926
      this.sanitizedSendUri_ + '#' + this.cycle_ + encodeURIComponent(payload);
927

928
  // TODO(user) Find out if try/catch is still needed
929

930
  try {
931
    // safari doesn't allow to call location.replace()
932
    if (goog.userAgent.WEBKIT) {
933
      this.sendFrame_.location.href = url;
934
    } else {
935
      this.sendFrame_.location.replace(url);
936
    }
937
  } catch (e) {
938
    goog.log.error(goog.net.xpc.logger, 'sending failed', e);
939
  }
940

941
  // Restart receiver timer on short polling interval, to support use-cases
942
  // where we need to capture responses quickly.
943
  goog.net.xpc.IframePollingTransport.startRcvTimer_();
944
};
945

946

947

948
/**
949
 * goog.net.xpc.IframePollingTransport.Receiver
950
 *
951
 * @constructor
952
 * @param {goog.net.xpc.IframePollingTransport} transport The transport to
953
 *     receive from.
954
 * @param {Object} windowObj The window-object to poll for location-changes.
955
 * @param {Function} callback The callback-function to be called when
956
 *     location has changed.
957
 * @final
958
 */
959
goog.net.xpc.IframePollingTransport.Receiver = function(
960
    transport, windowObj, callback) {
961
  /**
962
   * The transport to receive from.
963
   * @type {goog.net.xpc.IframePollingTransport}
964
   * @private
965
   */
966
  this.transport_ = transport;
967
  this.rcvFrame_ = windowObj;
968

969
  this.cb_ = callback;
970
  this.currentLoc_ = this.rcvFrame_.location.href.split('#')[0] + '#INITIAL';
971

972
  goog.net.xpc.IframePollingTransport.receivers_.push(this);
973
  goog.net.xpc.IframePollingTransport.startRcvTimer_();
974
};
975

976

977
/**
978
 * Polls the location of the receiver-frame for changes.
979
 * @return {boolean} Whether a change has been detected.
980
 */
981
goog.net.xpc.IframePollingTransport.Receiver.prototype.receive = function() {
982
  var loc = this.rcvFrame_.location.href;
983

984
  if (loc != this.currentLoc_) {
985
    this.currentLoc_ = loc;
986
    var payload = loc.split('#')[1];
987
    if (payload) {
988
      payload = payload.substr(1);  // discard first character (cycle)
989
      this.cb_(decodeURIComponent(payload));
990
    }
991
    return true;
992
  } else {
993
    return false;
994
  }
995
};
996

997