gecko/dom/base/ConsoleAPIStorage.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

let Cu = Components.utils;
let Ci = Components.interfaces;
let Cc = Components.classes;

Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/Services.jsm");

const STORAGE_MAX_EVENTS = 200;

var EXPORTED_SYMBOLS = ["ConsoleAPIStorage"];

var _consoleStorage = {};

/**
 * The ConsoleAPIStorage is meant to cache window.console API calls for later
 * reuse by other components when needed. For example, the Web Console code can
 * display the cached messages when it opens for the active tab.
 *
 * ConsoleAPI messages are stored as they come from the ConsoleAPI code, with
 * all their properties. They are kept around until the inner window object that
 * created the messages is destroyed. Messages are indexed by the inner window
 * ID.
 *
 * Usage:
 *    Cu.import("resource://gre/modules/ConsoleAPIStorage.jsm");
 *
 *    // Get the cached events array for the window you want (use the inner
 *    // window ID).
 *    let events = ConsoleAPIStorage.getEvents(innerWindowID);
 *    events.forEach(function(event) { ... });
 *
 *    // Clear the events for the given inner window ID.
 *    ConsoleAPIStorage.clearEvents(innerWindowID);
 */
var ConsoleAPIStorage = {

  QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),

  /** @private */
  observe: function CS_observe(aSubject, aTopic, aData)
  {
    if (aTopic == "xpcom-shutdown") {
      Services.obs.removeObserver(this, "xpcom-shutdown");
      Services.obs.removeObserver(this, "inner-window-destroyed");
      Services.obs.removeObserver(this, "memory-pressure");
      delete _consoleStorage;
    }
    else if (aTopic == "inner-window-destroyed") {
      let innerWindowID = aSubject.QueryInterface(Ci.nsISupportsPRUint64).data;
      this.clearEvents(innerWindowID);
    }
    else if (aTopic == "memory-pressure") {
      if (aData == "low-memory") {
        this.clearEvents();
      }
    }
  },

  /** @private */
  init: function CS_init()
  {
    Services.obs.addObserver(this, "xpcom-shutdown", false);
    Services.obs.addObserver(this, "inner-window-destroyed", false);
    Services.obs.addObserver(this, "memory-pressure", false);
  },

  /**
   * Get the events array by inner window ID.
   *
   * @param string aId
   *        The inner window ID for which you want to get the array of cached
   *        events.
   * @returns array
   *          The array of cached events for the given window.
   */
  getEvents: function CS_getEvents(aId)
  {
    return (_consoleStorage[aId] || []).slice(0);
  },

  /**
   * Record an event associated with the given window ID.
   *
   * @param string aWindowID
   *        The ID of the inner window for which the event occurred.
   * @param object aEvent
   *        A JavaScript object you want to store.
   */
  recordEvent: function CS_recordEvent(aWindowID, aEvent)
  {
    let ID = parseInt(aWindowID);
    if (isNaN(ID)) {
      throw new Error("Invalid window ID argument");
    }

    if (!_consoleStorage[ID]) {
      _consoleStorage[ID] = [];
    }
    let storage = _consoleStorage[ID];
    storage.push(aEvent);

    // truncate
    if (storage.length > STORAGE_MAX_EVENTS) {
      storage.shift();
    }

    Services.obs.notifyObservers(aEvent, "console-storage-cache-event", ID);
  },

  /**
   * Clear storage data for the given window.
   *
   * @param string [aId]
   *        Optional, the inner window ID for which you want to clear the
   *        messages. If this is not specified all of the cached messages are
   *        cleared, from all window objects.
   */
  clearEvents: function CS_clearEvents(aId)
  {
    if (aId != null) {
      delete _consoleStorage[aId];
    }
    else {
      _consoleStorage = {};
      Services.obs.notifyObservers(null, "console-storage-reset", null);
    }
  },
};

ConsoleAPIStorage.init();