1 files changed, 108 insertions, 0 deletions
diff --git a/image/DecodePool.h b/image/DecodePool.h
new file mode 100644
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--- /dev/null
+++ b/image/DecodePool.h
@@ -0,0 +1,108 @@
+/* -*- 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 nsIEventTarget interface to the thread pool's I/O thread.
+   */
+  already_AddRefed<nsIEventTarget> 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