1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/parser/html/nsHtml5StreamListener.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,54 @@
1.4 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.5 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.6 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.7 +
1.8 +#ifndef nsHtml5StreamListener_h
1.9 +#define nsHtml5StreamListener_h
1.10 +
1.11 +#include "nsIStreamListener.h"
1.12 +#include "nsIThreadRetargetableStreamListener.h"
1.13 +#include "nsHtml5RefPtr.h"
1.14 +#include "nsHtml5StreamParser.h"
1.15 +
1.16 +/**
1.17 + * The purpose of this class is to reconcile the problem that
1.18 + * nsHtml5StreamParser is a cycle collection participant, which means that it
1.19 + * can only be refcounted on the main thread, but
1.20 + * nsIThreadRetargetableStreamListener can be refcounted from another thread,
1.21 + * so nsHtml5StreamParser being an nsIThreadRetargetableStreamListener was
1.22 + * a memory corruption problem.
1.23 + *
1.24 + * mDelegate is an nsHtml5RefPtr, which releases the object that it points
1.25 + * to from a runnable on the main thread. DropDelegate() is only called on
1.26 + * the main thread. This call will finish before the main-thread derefs the
1.27 + * nsHtml5StreamListener itself, so there is no risk of another thread making
1.28 + * the refcount of nsHtml5StreamListener go to zero and running the destructor
1.29 + * concurrently. Other than that, the thread-safe nsISupports implementation
1.30 + * takes care of the destructor not running concurrently from different
1.31 + * threads, so there is no need to have a mutex around nsHtml5RefPtr to
1.32 + * prevent it from double-releasing nsHtml5StreamParser.
1.33 + */
1.34 +class nsHtml5StreamListener : public nsIStreamListener,
1.35 + public nsIThreadRetargetableStreamListener
1.36 +{
1.37 +public:
1.38 + nsHtml5StreamListener(nsHtml5StreamParser* aDelegate);
1.39 + virtual ~nsHtml5StreamListener();
1.40 +
1.41 + NS_DECL_THREADSAFE_ISUPPORTS
1.42 + NS_DECL_NSIREQUESTOBSERVER
1.43 + NS_DECL_NSISTREAMLISTENER
1.44 + NS_DECL_NSITHREADRETARGETABLESTREAMLISTENER
1.45 +
1.46 + inline nsHtml5StreamParser* GetDelegate()
1.47 + {
1.48 + return mDelegate;
1.49 + }
1.50 +
1.51 + void DropDelegate();
1.52 +
1.53 +private:
1.54 + nsHtml5RefPtr<nsHtml5StreamParser> mDelegate;
1.55 +};
1.56 +
1.57 +#endif // nsHtml5StreamListener_h
