chrome/browser/resources/pdf/background.js

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 (function() {
   6   'use strict';
   7
   8   /**
   9    * The timeout in ms before which a stream is closed.
  10    * @const {number}
  11    */
  12   var STREAM_TIMEOUT = 10000;
  13
  14   /**
  15    * A map of view ID (which identifies a particular PDF viewer instance) to
  16    * stream object.
  17    * @type {Object.<string, Object>}
  18    */
  19   var streams = {};
  20
  21   /**
  22    * A map of view ID (which identifies a particular PDF viewer instance) to
  23    * initialization function for that view.
  24    * @type {Object.<string, Function>}
  25    */
  26   var pluginInitFunctions = {};
  27
  28   /**
  29    * If we have received a stream object and an initialization function for a
  30    * particular PDF viewer instance we know that the extension has loaded in
  31    * and we can pass it the stream. We can then delete the corresponding map
  32    * entries.
  33    * @param {string} viewId The ID of the view to initialize with a stream.
  34    * @return {boolean} Whether the stream has been sent to the viewer.
  35    */
  36   function flush(viewId) {
  37     if (viewId in streams && viewId in pluginInitFunctions) {
  38       var streamDetails = streams[viewId];
  39       // If the stream has been aborted we pass the stream details to the PDF
  40       // viewer with the stream URL removed. This allows the viewer to report an
  41       // error to the user rather than trying to load from an invalid stream
  42       // URL.
  43       if (streamDetails.aborted)
  44         delete streamDetails.streamUrl;
  45       pluginInitFunctions[viewId](streamDetails);
  46       delete streams[viewId];
  47       delete pluginInitFunctions[viewId];
  48       if (!streamDetails.aborted) {
  49         // Once a stream has been opened, by the plugin, it is safe to abort.
  50         // Abort after STREAM_TIMEOUT in case the plugin was closed without
  51         // reading from the stream.
  52         //
  53         // This is a temporary work-around until the streamsPrivate API is made
  54         // more robust to its clients failing to finish reading from or abort
  55         // streams.
  56         setTimeout(function() {
  57           chrome.streamsPrivate.abort(streamDetails.streamUrl);
  58         }, STREAM_TIMEOUT);
  59       }
  60       return true;
  61     }
  62     return false;
  63   }
  64
  65   /**
  66    * This is called when loading a document with the PDF mime type and passes a
  67    * stream that points to the PDF file. This may be run before or after we
  68    * receive a message from the PDF viewer with its initialization function.
  69    */
  70   chrome.streamsPrivate.onExecuteMimeTypeHandler.addListener(
  71     function(streamDetails) {
  72       // Store the stream until we are contacted by the PDF viewer that owns the
  73       // stream.
  74       streams[streamDetails.viewId] = streamDetails;
  75       if (!flush(streamDetails.viewId)) {
  76         // If a stream has not been claimed by a PDF viewer instance within
  77         // STREAM_TIMEOUT, abort the stream.
  78         setTimeout(function() {
  79           if (streamDetails.viewId in streams) {
  80             chrome.streamsPrivate.abort(streamDetails.streamUrl);
  81             streamDetails.aborted = true;
  82           }
  83         }, STREAM_TIMEOUT);
  84       }
  85     }
  86   );
  87
  88   /**
  89    * This is called when we receive a message from the PDF viewer indicating
  90    * it has loaded and is ready to receive a stream of the data.
  91    */
  92   chrome.runtime.onMessage.addListener(
  93     function(request, sender, responseFunction) {
  94       // Store the initialization function until we receive the stream which
  95       // corresponds to the PDF viewer.
  96       pluginInitFunctions[request.viewId] = responseFunction;
  97       flush(request.viewId);
  98     }
  99   );
 100 }());