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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */
/**
* DecodePool manages the threads used for decoding raster images.
*/
#ifndef mozilla_image_DecodePool_h
#define mozilla_image_DecodePool_h
#include "mozilla/Mutex.h"
#include "mozilla/StaticPtr.h"
#include "nsCOMArray.h"
#include "nsCOMPtr.h"
#include "nsIEventTarget.h"
#include "nsIObserver.h"
#include "mozilla/RefPtr.h"
#include "nsStringFwd.h"
class nsIThread;
class nsIThreadPool;
namespace mozilla {
namespace image {
class Decoder;
class DecodePoolImpl;
class IDecodingTask;
/**
* DecodePool is a singleton class that manages decoding of raster images. It
* owns a pool of image decoding threads that are used for asynchronous
* decoding.
*
* DecodePool allows callers to run a decoder, handling management of the
* decoder's lifecycle and whether it executes on the main thread,
* off-main-thread in the image decoding thread pool, or on some combination of
* the two.
*/
class DecodePool final : public nsIObserver {
public:
NS_DECL_THREADSAFE_ISUPPORTS
NS_DECL_NSIOBSERVER
/// Initializes the singleton instance. Should be called from the main thread.
static void Initialize();
/// Returns the singleton instance.
static DecodePool* Singleton();
/// @return the number of processor cores we have available. This is not the
/// same as the number of decoding threads we're actually using.
static uint32_t NumberOfCores();
/// True if the DecodePool is being shutdown. This may only be called by
/// threads from the pool to check if they should keep working or not.
bool IsShuttingDown() const;
/// Ask the DecodePool to run @aTask asynchronously and return immediately.
void AsyncRun(IDecodingTask* aTask);
/**
* Run @aTask synchronously if the task would prefer it. It's up to the task
* itself to make this decision; @see IDecodingTask::ShouldPreferSyncRun(). If
* @aTask doesn't prefer it, just run @aTask asynchronously and return
* immediately.
* @return true if the task was run sync, false otherwise.
*/
bool SyncRunIfPreferred(IDecodingTask* aTask, const nsCString& aURI);
/**
* Run @aTask synchronously. This does not guarantee that @aTask will complete
* synchronously. If, for example, @aTask doesn't yet have the data it needs
* to run synchronously, it may recover by scheduling an async task to finish
* up the work when the remaining data is available.
*/
void SyncRunIfPossible(IDecodingTask* aTask, const nsCString& aURI);
/**
* Returns an event target interface to the DecodePool's I/O thread. Callers
* who want to deliver data to workers on the DecodePool can use this event
* target.
*
* @return An nsISerialEventTarget interface to the thread pool's I/O thread.
*/
already_AddRefed<nsISerialEventTarget> GetIOEventTarget();
private:
friend class DecodePoolWorker;
DecodePool();
virtual ~DecodePool();
static StaticRefPtr<DecodePool> sSingleton;
static uint32_t sNumCores;
bool mShuttingDown = false;
// mMutex protects mIOThread.
Mutex mMutex;
nsCOMPtr<nsIThread> mIOThread MOZ_GUARDED_BY(mMutex);
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_DecodePool_h
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