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 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim:set ts=2 sw=2 sts=2 et cindent: */

 /* 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/. */

 #ifndef SharedThreadPool_h_

 #define SharedThreadPool_h_

 #include <queue>

 #include "mozilla/RefPtr.h"

 #include "nsThreadUtils.h"

 #include "nsIThreadPool.h"

 #include "nsISupports.h"

 #include "nsISupportsImpl.h"

 #include "nsCOMPtr.h"

 namespace mozilla {

 // Wrapper that makes an nsIThreadPool a singleton, and provides a

 // consistent threadsafe interface to get instances. Callers simply get a

 // SharedThreadPool by the name of its nsIThreadPool. All get requests of

 // the same name get the same SharedThreadPool. Users must store a reference

 // to the pool, and when the last reference to a SharedThreadPool is dropped

 // the pool is shutdown and deleted. Users aren't required to manually

 // shutdown the pool, and can release references on any thread. On Windows

 // all threads in the pool have MSCOM initialized with COINIT_MULTITHREADED.

 class SharedThreadPool : public nsIThreadPool

 {

 public:

   // Gets (possibly creating) the shared thread pool singleton instance with

   // thread pool named aName.

   // *Must* be called on the main thread.

   static TemporaryRef<SharedThreadPool> Get(const nsCString& aName,

                                             uint32_t aThreadLimit = 4);

   // Spins the event loop until all thread pools are shutdown.

   // *Must* be called on the main thread.

   static void SpinUntilShutdown();

   // We implement custom threadsafe AddRef/Release pair, that destroys the

   // the shared pool singleton when the refcount drops to 0. The addref/release

   // are implemented using locking, so it's not recommended that you use them

   // in a tight loop.

   NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr);

   NS_IMETHOD_(MozExternalRefCountType) AddRef(void);

   NS_IMETHOD_(MozExternalRefCountType) Release(void);

   // Forward behaviour to wrapped thread pool implementation.

   NS_FORWARD_SAFE_NSITHREADPOOL(mPool);

   NS_FORWARD_SAFE_NSIEVENTTARGET(GetEventTarget());

   nsIEventTarget* GetEventTarget() {

     return mEventTarget;

   }

 private:

   // Creates necessary statics.

   // Main thread only.

   static void EnsureInitialized();

   // Creates a singleton SharedThreadPool wrapper around aPool.

   // aName is the name of the aPool, and is used to lookup the

   // SharedThreadPool in the hash table of all created pools.

   SharedThreadPool(const nsCString& aName,

                    nsIThreadPool* aPool);

   virtual ~SharedThreadPool();

   nsresult EnsureThreadLimitIsAtLeast(uint32_t aThreadLimit);

   // Name of mPool.

   const nsCString mName;

   // Thread pool being wrapped.

   nsCOMPtr<nsIThreadPool> mPool;

   // Refcount. We implement custom ref counting so that the thread pool is

   // shutdown in a threadsafe manner and singletonness is preserved.

   nsrefcnt mRefCnt;

   // mPool QI'd to nsIEventTarget. We cache this, so that we can use

   // NS_FORWARD_SAFE_NSIEVENTTARGET above.

   nsCOMPtr<nsIEventTarget> mEventTarget;

 };

 } // namespace mozilla

 #endif // SharedThreadPool_h_