The Tor Browser: parser/html/nsHtml5StreamListener.h@8bccb770b82d

     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/. */

     5 #ifndef nsHtml5StreamListener_h

     6 #define nsHtml5StreamListener_h

     8 #include "nsIStreamListener.h"

     9 #include "nsIThreadRetargetableStreamListener.h"

    10 #include "nsHtml5RefPtr.h"

    11 #include "nsHtml5StreamParser.h"

    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 nsHtml5RefPtr, 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 nsHtml5RefPtr to

    29  * prevent it from double-releasing nsHtml5StreamParser.

    30  */

    31 class nsHtml5StreamListener : public nsIStreamListener,

    32                               public nsIThreadRetargetableStreamListener

    33 {

    34 public:

    35   nsHtml5StreamListener(nsHtml5StreamParser* aDelegate);

    36   virtual ~nsHtml5StreamListener();

    38   NS_DECL_THREADSAFE_ISUPPORTS

    39   NS_DECL_NSIREQUESTOBSERVER

    40   NS_DECL_NSISTREAMLISTENER

    41   NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER

    43   inline nsHtml5StreamParser* GetDelegate()

    44   {

    45     return mDelegate;

    46   }

    48   void DropDelegate();

    50 private:

    51   nsHtml5RefPtr<nsHtml5StreamParser> mDelegate;

    52 };

    54 #endif // nsHtml5StreamListener_h

The Tor Browser / file revision