nsupdateservice.js

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                          umUpdate.buildID == update.buildID) {
            umUpdate.statusText = update.statusText;
            break;
          }
        }

        LOG("UpdateService", "_postUpdateProcessing: Install Succeeded, Showing UI");
        prompter.showUpdateInstalled(update);

//@line 1214 "/c/builds/1813/mozilla/toolkit/mozapps/update/src/nsUpdateService.js.in"

        // Done with this update. Clean it up.
        cleanupActiveUpdate(updRootKey);
      }
      else {
        // If we hit an error, then the error code will be included in the
        // status string following a colon.  If we had an I/O error, then we
        // assume that the patch is not invalid, and we restage the patch so
        // that it can be attempted again the next time we restart.
        var ary = status.split(": ");
        update.state = ary[0];
        if (update.state == STATE_FAILED && ary[1]) {
          update.errorCode = ary[1];
          if (update.errorCode == WRITE_ERROR) {
            prompter.showUpdateError(update);
            writeStatusFile(getUpdatesDir(), update.state = STATE_PENDING);
            return;
          }
        }

        // Something went wrong with the patch application process.
        cleanupActiveUpdate();

        update.statusText = bundle.GetStringFromName("patchApplyFailure");
        var oldType = update.selectedPatch ? update.selectedPatch.type 
                                           : "complete";
        if (update.selectedPatch && oldType == "partial") {
          // Partial patch application failed, try downloading the complete
          // update in the background instead.
          LOG("UpdateService", "_postUpdateProcessing: Install of Partial Patch " + 
              "failed, downloading Complete Patch and maybe showing UI");
          var status = this.downloadUpdate(update, true);
          if (status == STATE_NONE)
            cleanupActiveUpdate();
        }
        else {
          LOG("UpdateService", "_postUpdateProcessing: Install of Complete or " + 
              "only patch failed. Showing error.");
        }
        update.QueryInterface(Components.interfaces.nsIWritablePropertyBag);
        update.setProperty("patchingFailed", oldType);
        prompter.showUpdateError(update);
      }
    }
    else {
      LOG("UpdateService", "_postUpdateProcessing: No Status, No Update");
    }
  },

  /**
   * Initialize Logging preferences, formatted like so:
   *  app.update.log.<moduleName> = <true|false>
   */
  _initLoggingPrefs: function() {
    try {
      var ps = Components.classes["@mozilla.org/preferences-service;1"]
                        .getService(Components.interfaces.nsIPrefService);
      var logBranch = ps.getBranch(PREF_APP_UPDATE_LOG_BRANCH);
      var modules = logBranch.getChildList("", { value: 0 });

      for (var i = 0; i < modules.length; ++i) {
        if (logBranch.prefHasUserValue(modules[i]))
          gLogEnabled[modules[i]] = logBranch.getBoolPref(modules[i]);
      }
    }
    catch (e) {
    }
  },
  
  /**
   *
   */
  _needsToPromptForUpdate: function(updates) {
    // First, check for Extension incompatibilities. These trump any preference
    // settings.
    var em = Components.classes["@mozilla.org/extensions/manager;1"]
                       .getService(Components.interfaces.nsIExtensionManager);
    var incompatibleList = { };
    for (var i = 0; i < updates.length; ++i) {
      var count = {};
      em.getIncompatibleItemList(gApp.ID, updates[i].extensionVersion,
                                 nsIUpdateItem.TYPE_ADDON, false, count);
      if (count.value > 0)
        return true;
    }

    // Now, inspect user preferences.
    
    // No prompt necessary, silently update...
    return false;
  },
  
  /**
   * Notified when a timer fires
   * @param   timer
   *          The timer that fired
   */
  notify: function(timer) {
    // If a download is in progress, then do nothing.
    if (this.isDownloading || this._downloader && this._downloader.patchIsStaged)
      return;

    var self = this;
    var listener = {
      /**
       * See nsIUpdateService.idl
       */
      onProgress: function(request, position, totalSize) { 
      },
      
      /**
       * See nsIUpdateService.idl
       */
      onCheckComplete: function(request, updates, updateCount) {
        self._selectAndInstallUpdate(updates);
      },

      /**
       * See nsIUpdateService.idl
       */
      onError: function(request, update) { 
        LOG("Checker", "Error during background update: " + update.statusText);
      },
    }
    this.backgroundChecker.checkForUpdates(listener, false);
  },
  
  /**
   * Determine whether or not an update requires user confirmation before it
   * can be installed.
   * @param   update
   *          The update to be installed
   * @returns true if a prompt UI should be shown asking the user if they want
   *          to install the update, false if the update should just be 
   *          silently downloaded and installed.
   */
  _shouldPrompt: function(update) {
    // There are two possible outcomes here:
    // 1. download and install the update automatically
    // 2. alert the user about the presence of an update before doing anything
    //
    // The outcome we follow is determined as follows:
    // 
    // Note:  all Major updates require notification and confirmation
    // 
    // Update Type      Mode      Incompatible    Outcome
    // Major            0         Yes or No       Notify and Confirm
    // Major            1         No              Notify and Confirm
    // Major            1         Yes             Notify and Confirm
    // Major            2         Yes or No       Notify and Confirm
    // Minor            0         Yes or No       Auto Install
    // Minor            1         No              Auto Install
    // Minor            1         Yes             Notify and Confirm
    // Minor            2         No              Auto Install
    // Minor            2         Yes             Notify and Confirm
    //
    // In addition, if there is a license associated with an update, regardless
    // of type it must be agreed to. 
    //
    // If app.update.enabled is set to false, an update check is not performed
    // at all, and so none of the decision making above is entered into.
    //
    if (update.type == "major") {
      LOG("Checker", "_shouldPrompt: Prompting because it is a major update");
      return true;
    }

    update.QueryInterface(Components.interfaces.nsIPropertyBag);
    try {
      var licenseAccepted = update.getProperty("licenseAccepted") == "true";
    }
    catch (e) {
      licenseAccepted = false;
    }

    var updateEnabled = getPref("getBoolPref", PREF_APP_UPDATE_ENABLED, true);
    if (!updateEnabled) {
      LOG("Checker", "_shouldPrompt: Not prompting because update is " + 
          "disabled");
      return false;
    }
    
    // User has turned off automatic download and install
    var autoEnabled = getPref("getBoolPref", PREF_APP_UPDATE_AUTO, true);
    if (!autoEnabled) {
      LOG("Checker", "_shouldPrompt: Prompting because auto install is disabled");
      return true;
    }
    
    switch (getPref("getIntPref", PREF_APP_UPDATE_MODE, 1)) {
    case 1:
      // Mode 1 is do not prompt only if there are no incompatibilities
      // releases
      LOG("Checker", "_shouldPrompt: Prompting if there are incompatibilities");
      return !isCompatible(update);
    case 2:
      // Mode 2 is do not prompt only if there are no incompatibilities
      LOG("Checker", "_shouldPrompt: Prompting if there are incompatibilities");
      return !isCompatible(update);
    }
    // Mode 0 is do not prompt regardless of incompatibilities
    LOG("Checker", "_shouldPrompt: Not prompting the user - they choose to " +
        "ignore incompatibilities");
    return false;
  },
  
  /**
   * Determine which of the specified updates should be installed.
   * @param   updates
   *          An array of available updates
   */
  selectUpdate: function(updates) {
    if (updates.length == 0)
      return null;
    
    // Choose the newest of the available minor and major updates. 
    var majorUpdate = null, minorUpdate = null;
    var newestMinor = updates[0], newestMajor = updates[0];

    var vc = Components.classes["@mozilla.org/xpcom/version-comparator;1"]
                       .getService(Components.interfaces.nsIVersionComparator);
    for (var i = 0; i < updates.length; ++i) {
      if (updates[i].type == "major" && 
          vc.compare(newestMajor.version, updates[i].version) <= 0)
        majorUpdate = newestMajor = updates[i];
      if (updates[i].type == "minor" && 
          vc.compare(newestMinor.version, updates[i].version) <= 0)
        minorUpdate = newestMinor = updates[i];
    }

    // IMPORTANT
    // If there's a minor update, always try and fetch that one first, 
    // otherwise use the newest major update.
    // selectUpdate() only returns one update.
    // if major were to trump minor, and we said "never" to the major
    // we'd never get the minor update, since selectUpdate()
    // would return the major update that the user said "never" to
    // (shadowing the important minor update with security fixes)
    return minorUpdate || majorUpdate;
  },
  
  /**
   * Determine which of the specified updates should be installed and
   * begin the download/installation process, optionally prompting the
   * user for permission if required.
   * @param   updates
   *          An array of available updates
   */
  _selectAndInstallUpdate: function(updates) {
    // Don't prompt if there's an active update - the user is already 
    // aware and is downloading, or performed some user action to prevent
    // notification.
    var um = Components.classes["@mozilla.org/updates/update-manager;1"]
                       .getService(Components.interfaces.nsIUpdateManager);
    if (um.activeUpdate)
      return;
    
    var update = this.selectUpdate(updates, updates.length);
    if (!update)
      return;

    // check if the user said "never" to this version
    // this check is done here, and not in selectUpdate() so that
    // the user can get an upgrade they said "never" to if they
    // manually do "Check for Updates..."
    // note, selectUpdate() only returns one update.
    // but in selectUpdate(), minor updates trump major updates
    // if major trumps minor, and we said "never" to the major
    // we'd never see the minor update.
    // 
    // note, the never decision should only apply to major updates
    // see bug #350636 for a scenario where this could potentially
    // be an issue
    var neverPrefName = PREF_UPDATE_NEVER_BRANCH + update.version;
    var never = getPref("getBoolPref", neverPrefName, false);
    if (never && update.type == "major")
      return;

    if (this._shouldPrompt(update))
      showPromptIfNoIncompatibilities(update);
    else {
      LOG("UpdateService", "_selectAndInstallUpdate: No need to show prompt, just download update");
      var status = this.downloadUpdate(update, true);
      if (status == STATE_NONE)
        cleanupActiveUpdate();
    }
  },

  /**
   * The Checker used for background update checks.
   */
  _backgroundChecker: null,
  
  /**
   * See nsIUpdateService.idl
   */
  get backgroundChecker() {
    if (!this._backgroundChecker) 
      this._backgroundChecker = new Checker();
    return this._backgroundChecker;
  },
  
  /**
   * See nsIUpdateService.idl
   */
  get canUpdate() {
    try {
      var appDirFile = getUpdateFile([FILE_PERMS_TEST]);
      if (!appDirFile.exists()) {
        appDirFile.create(nsILocalFile.NORMAL_FILE_TYPE, PERMS_FILE);
        appDirFile.remove(false);
      }
      var updateDir = getUpdatesDir();
      var upDirFile = updateDir.clone();
      upDirFile.append(FILE_PERMS_TEST);
      if (!upDirFile.exists()) {
        upDirFile.create(nsILocalFile.NORMAL_FILE_TYPE, PERMS_FILE);
        upDirFile.remove(false);
      }
    }
    catch (e) {
      // No write privileges to install directory
      return false;
    }
    // If the administrator has locked the app update functionality 
    // OFF - this is not just a user setting, so disable the manual
    // UI too.
    var enabled = getPref("getBoolPref", PREF_APP_UPDATE_ENABLED, true);
    if (!enabled && gPref.prefIsLocked(PREF_APP_UPDATE_ENABLED))
      return false;

    // If we don't know the binary platform we're updating, we can't update.
    if (!gABI)
      return false;

    // If we don't know the OS version we're updating, we can't update.
    if (!gOSVersion)
      return false;

    return true;
  },
  
  /**
   * See nsIUpdateService.idl
   */
  addDownloadListener: function(listener) {
    if (!this._downloader) {
      LOG("UpdateService", "addDownloadListener: no downloader!\n");
      return;
    }
    this._downloader.addDownloadListener(listener);
  },
  
  /**
   * See nsIUpdateService.idl
   */
  removeDownloadListener: function(listener) {
    if (!this._downloader) {
      LOG("UpdateService", "removeDownloadListener: no downloader!\n");
      return;
    }
    this._downloader.removeDownloadListener(listener);
  },
  
  /**
   * See nsIUpdateService.idl
   */
  downloadUpdate: function(update, background) {
    if (!update)
      throw Components.results.NS_ERROR_NULL_POINTER;
    if (this.isDownloading) {
      if (update.isCompleteUpdate == this._downloader.isCompleteUpdate &&
          background == this._downloader.background) {
        LOG("UpdateService", "no support for downloading more than one update at a time");
        return readStatusFile(getUpdatesDir());
      }
      this._downloader.cancel();
    }
    this._downloader = new Downloader(background);
    return this._downloader.downloadUpdate(update);
  },
  
  /**
   * See nsIUpdateService.idl
   */
  pauseDownload: function() {
    if (this.isDownloading)
      this._downloader.cancel();
  },
  
  /**
   * See nsIUpdateService.idl
   */
  get isDownloading() {
    return this._downloader && this._downloader.isBusy;
  },
  
  /**