dom/localstorage/LSObserver.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_dom_localstorage_LSObserver_h
   8 #define mozilla_dom_localstorage_LSObserver_h
   9
  10 #include "mozilla/Assertions.h"
  11 #include "nsISupports.h"
  12 #include "nsString.h"
  13
  14 namespace mozilla::dom {
  15
  16 class LSObserverChild;
  17
  18 /**
  19  * Effectively just a refcounted life-cycle management wrapper around
  20  * LSObserverChild which exists to receive "storage" event information from
  21  * other processes.  (Same-process events are handled within the process, see
  22  * `LSObject::OnChange`.)
  23  *
  24  * ## Lifecycle ##
  25  * - Created by LSObject::EnsureObserver via synchronous LSRequest idiom
  26  *   whenever the first window's origin adds a "storage" event.  Placed in the
  27  *   gLSObservers LSObserverHashtable for subsequent LSObject's via
  28  *   LSObserver::Get lookup.
  29  * - The LSObserverChild directly handles "Observe" messages, shunting them
  30  *   directly to Storage::NotifyChange which does all the legwork of notifying
  31  *   windows about "storage" events.
  32  * - Destroyed when refcount goes to zero due to all owning LSObjects being
  33  *   destroyed or having their `LSObject::DropObserver` methods invoked due to
  34  *   the last "storage" event listener being removed from the owning window.
  35  */
  36 class LSObserver final {
  37   friend class LSObject;
  38
  39   LSObserverChild* mActor;
  40
  41   const nsCString mOrigin;
  42
  43  public:
  44   static LSObserver* Get(const nsACString& aOrigin);
  45
  46   NS_INLINE_DECL_REFCOUNTING(LSObserver)
  47
  48   void AssertIsOnOwningThread() const { NS_ASSERT_OWNINGTHREAD(LSObserver); }
  49
  50   void SetActor(LSObserverChild* aActor);
  51
  52   void ClearActor() {
  53     AssertIsOnOwningThread();
  54     MOZ_ASSERT(mActor);
  55
  56     mActor = nullptr;
  57   }
  58
  59  private:
  60   // Only created by LSObject.
  61   explicit LSObserver(const nsACString& aOrigin);
  62
  63   ~LSObserver();
  64 };
  65
  66 }  // namespace mozilla::dom
  67
  68 #endif  // mozilla_dom_localstorage_LSObserver_h