Line data    Source code

       1             : /* This Source Code Form is subject to the terms of the Mozilla Public
       2             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       3             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       4             : 
       5             : #ifndef nsHtml5StreamListener_h
       6             : #define nsHtml5StreamListener_h
       7             : 
       8             : #include "nsIStreamListener.h"
       9             : #include "nsIThreadRetargetableStreamListener.h"
      10             : #include "nsHtml5StreamParserPtr.h"
      11             : #include "nsHtml5StreamParser.h"
      12             : 
      13             : /**
      14             :  * The purpose of this class is to reconcile the problem that
      15             :  * nsHtml5StreamParser is a cycle collection participant, which means that it
      16             :  * can only be refcounted on the main thread, but
      17             :  * nsIThreadRetargetableStreamListener can be refcounted from another thread,
      18             :  * so nsHtml5StreamParser being an nsIThreadRetargetableStreamListener was
      19             :  * a memory corruption problem.
      20             :  *
      21             :  * mDelegate is an nsHtml5StreamParserPtr, which releases the object that it points
      22             :  * to from a runnable on the main thread. DropDelegate() is only called on
      23             :  * the main thread. This call will finish before the main-thread derefs the
      24             :  * nsHtml5StreamListener itself, so there is no risk of another thread making
      25             :  * the refcount of nsHtml5StreamListener go to zero and running the destructor
      26             :  * concurrently. Other than that, the thread-safe nsISupports implementation
      27             :  * takes care of the destructor not running concurrently from different
      28             :  * threads, so there is no need to have a mutex around nsHtml5StreamParserPtr to
      29             :  * prevent it from double-releasing nsHtml5StreamParser.
      30             :  */
      31             : class nsHtml5StreamListener : public nsIStreamListener,
      32             :                               public nsIThreadRetargetableStreamListener
      33             : {
      34             : public:
      35             :   explicit nsHtml5StreamListener(nsHtml5StreamParser* aDelegate);
      36             : 
      37             :   NS_DECL_THREADSAFE_ISUPPORTS
      38             :   NS_DECL_NSIREQUESTOBSERVER
      39             :   NS_DECL_NSISTREAMLISTENER
      40             :   NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
      41             : 
      42          35 :   inline nsHtml5StreamParser* GetDelegate()
      43             :   {
      44          35 :     return mDelegate;
      45             :   }
      46             : 
      47             :   void DropDelegate();
      48             : 
      49             : private:
      50             :   virtual ~nsHtml5StreamListener();
      51             : 
      52             :   nsHtml5StreamParserPtr mDelegate;
      53             : };
      54             : 
      55             : #endif // nsHtml5StreamListener_h