gecko-dev/content/media/SharedThreadPool.h

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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(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_