tor-browser

ConsoleAPIStorage.sys.mjs (6360B)

---

/* 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/. */

const STORAGE_MAX_EVENTS = 1000;

var _consoleStorage = new Map();

// NOTE: these listeners used to just be added as observers and notified via
// Services.obs.notifyObservers. However, that has enough overhead to be a
// problem for this. Using an explicit global array is much cheaper, and
// should be equivalent.
var _logEventListeners = [];

const CONSOLEAPISTORAGE_CID = Components.ID(
 "{96cf7855-dfa9-4c6d-8276-f9705b4890f2}"
);

/**
* 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:
*    let ConsoleAPIStorage = Cc["@mozilla.org/consoleAPI-storage;1"]
*                              .getService(Ci.nsIConsoleAPIStorage);
*
*    // 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);
*/
export function ConsoleAPIStorageService() {
 this.init();
}

ConsoleAPIStorageService.prototype = {
 classID: CONSOLEAPISTORAGE_CID,
 QueryInterface: ChromeUtils.generateQI([
   "nsIConsoleAPIStorage",
   "nsIObserver",
 ]),

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

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

 /**
  * Get the events array by inner window ID or all events from all windows.
  *
  * @param string [aId]
  *        Optional, 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. If no |aId| is
  *          given this function returns all of the cached events, from any
  *          window.
  */
 getEvents: function CS_getEvents(aId) {
   if (aId != null) {
     return (_consoleStorage.get(aId) || []).slice(0);
   }

   let result = [];

   for (let [, events] of _consoleStorage) {
     result.push.apply(result, events);
   }

   return result.sort(function (a, b) {
     return a.timeStamp - b.timeStamp;
   });
 },

 /**
  * Adds a listener to be notified of log events.
  *
  * @param jsval [aListener]
  *        A JS listener which will be notified with the message object when
  *        a log event occurs.
  * @param nsIPrincipal [aPrincipal]
  *        The principal of the listener - used to determine if we need to
  *        clone the message before forwarding it.
  */
 addLogEventListener: function CS_addLogEventListener(aListener, aPrincipal) {
   // If our listener has a less-privileged principal than us, then they won't
   // be able to access the log event object which was populated for our
   // scope. Accordingly we need to clone it for these listeners.
   //
   // XXX: AFAICT these listeners which we need to clone messages for are all
   // tests. Alternative solutions are welcome.
   const clone = !aPrincipal.subsumes(
     Cc["@mozilla.org/systemprincipal;1"].createInstance(Ci.nsIPrincipal)
   );
   _logEventListeners.push({
     callback: aListener,
     clone,
   });
 },

 /**
  * Removes a listener added with `addLogEventListener`.
  *
  * @param jsval [aListener]
  *        A JS listener which was added with `addLogEventListener`.
  */
 removeLogEventListener: function CS_removeLogEventListener(aListener) {
   const index = _logEventListeners.findIndex(l => l.callback === aListener);
   if (index != -1) {
     _logEventListeners.splice(index, 1);
   } else {
     console.error(
       "Attempted to remove a log event listener that does not exist."
     );
   }
 },

 /**
  * Record an event associated with the given window ID.
  *
  * @param string aId
  *        The ID of the inner window for which the event occurred or "jsm" for
  *        messages logged from JavaScript modules..
  * @param object aEvent
  *        A JavaScript object you want to store.
  */
 recordEvent: function CS_recordEvent(aId, aEvent) {
   if (!_consoleStorage.has(aId)) {
     _consoleStorage.set(aId, []);
   }

   let storage = _consoleStorage.get(aId);

   storage.push(aEvent);

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

   for (let { callback, clone } of _logEventListeners) {
     try {
       if (clone) {
         callback(Cu.cloneInto(aEvent, callback));
       } else {
         callback(aEvent);
       }
     } catch (e) {
       // A failing listener should not prevent from calling other listeners.
       console.error(e);
     }
   }
 },

 /**
  * 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) {
     _consoleStorage.delete(aId);
   } else {
     _consoleStorage.clear();
     Services.obs.notifyObservers(null, "console-storage-reset");
   }
 },
};