michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef mozilla_imagelib_DiscardTracker_h_
michael@0: #define mozilla_imagelib_DiscardTracker_h_
michael@0: 
michael@0: #include "mozilla/Atomics.h"
michael@0: #include "mozilla/LinkedList.h"
michael@0: #include "mozilla/Mutex.h"
michael@0: #include "mozilla/TimeStamp.h"
michael@0: #include "prlock.h"
michael@0: #include "nsThreadUtils.h"
michael@0: #include "nsAutoPtr.h"
michael@0: 
michael@0: class nsITimer;
michael@0: 
michael@0: namespace mozilla {
michael@0: namespace image {
michael@0: 
michael@0: class RasterImage;
michael@0: 
michael@0: /**
michael@0:  * This static class maintains a linked list of RasterImage objects which are
michael@0:  * eligible for discarding.
michael@0:  *
michael@0:  * When Reset() is called, the node is removed from its position in the list
michael@0:  * (if it was there before) and appended to the beginnings of the list.
michael@0:  *
michael@0:  * Periodically (on a timer and when we notice that we're using more memory
michael@0:  * than we'd like for decoded images), we go through the list and discard
michael@0:  * decoded data from images at the end of the list.
michael@0:  */
michael@0: class DiscardTracker
michael@0: {
michael@0:   public:
michael@0:     /**
michael@0:      * The DiscardTracker keeps a linked list of Node objects.  Each object
michael@0:      * points to a RasterImage and contains a timestamp indicating when the
michael@0:      * node was inserted into the tracker.
michael@0:      *
michael@0:      * This structure is embedded within each RasterImage object, and we do
michael@0:      * |mDiscardTrackerNode.img = this| on RasterImage construction.  Thus, a
michael@0:      * RasterImage must always call DiscardTracker::Remove() in its destructor
michael@0:      * to avoid having the tracker point to bogus memory.
michael@0:      */
michael@0:     struct Node : public LinkedListElement<Node>
michael@0:     {
michael@0:       RasterImage *img;
michael@0:       TimeStamp timestamp;
michael@0:     };
michael@0: 
michael@0:     /**
michael@0:      * Add an image to the front of the tracker's list, or move it to the front
michael@0:      * if it's already in the list.  This function is main thread only.
michael@0:      */
michael@0:     static nsresult Reset(struct Node* node);
michael@0: 
michael@0:     /**
michael@0:      * Remove a node from the tracker; do nothing if the node is currently
michael@0:      * untracked.  This function is main thread only.
michael@0:      */
michael@0:     static void Remove(struct Node* node);
michael@0: 
michael@0:     /**
michael@0:      * Initializes the discard tracker.  This function is main thread only.
michael@0:      */
michael@0:     static nsresult Initialize();
michael@0: 
michael@0:     /**
michael@0:      * Shut the discard tracker down.  This should be called on XPCOM shutdown
michael@0:      * so we destroy the discard timer's nsITimer.  This function is main thread
michael@0:      * only.
michael@0:      */
michael@0:     static void Shutdown();
michael@0: 
michael@0:     /**
michael@0:      * Discard the decoded image data for all images tracked by the discard
michael@0:      * tracker.  This function is main thread only.
michael@0:      */
michael@0:     static void DiscardAll();
michael@0: 
michael@0:     /**
michael@0:      * Inform the discard tracker that we are going to allocate some memory
michael@0:      * for a decoded image. We use this to determine when we've allocated
michael@0:      * too much memory and should discard some images.  This function can be
michael@0:      * called from any thread and is thread-safe. If this function succeeds, the
michael@0:      * caller is now responsible for ensuring that InformDeallocation is called.
michael@0:      */
michael@0:     static bool TryAllocation(uint64_t aBytes);
michael@0: 
michael@0:     /**
michael@0:      * Inform the discard tracker that we've deallocated some memory for a
michael@0:      * decoded image. This function can be called from any thread and is
michael@0:      * thread-safe.
michael@0:      */
michael@0:     static void InformDeallocation(uint64_t aBytes);
michael@0: 
michael@0:   private:
michael@0:     /**
michael@0:      * This is called when the discard timer fires; it calls into DiscardNow().
michael@0:      */
michael@0:     friend void DiscardTimeoutChangedCallback(const char* aPref, void *aClosure);
michael@0: 
michael@0:     /**
michael@0:      * When run, this runnable sets sDiscardRunnablePending to false and calls
michael@0:      * DiscardNow().
michael@0:      */
michael@0:     class DiscardRunnable : public nsRunnable
michael@0:     {
michael@0:       NS_IMETHOD Run();
michael@0:     };
michael@0: 
michael@0:     static void ReloadTimeout();
michael@0:     static nsresult EnableTimer();
michael@0:     static void DisableTimer();
michael@0:     static void MaybeDiscardSoon();
michael@0:     static void TimerCallback(nsITimer *aTimer, void *aClosure);
michael@0:     static void DiscardNow();
michael@0: 
michael@0:     static LinkedList<Node> sDiscardableImages;
michael@0:     static nsCOMPtr<nsITimer> sTimer;
michael@0:     static bool sInitialized;
michael@0:     static bool sTimerOn;
michael@0:     static mozilla::Atomic<bool> sDiscardRunnablePending;
michael@0:     static uint64_t sCurrentDecodedImageBytes;
michael@0:     static uint32_t sMinDiscardTimeoutMs;
michael@0:     static uint32_t sMaxDecodedImageKB;
michael@0:     static uint32_t sHardLimitDecodedImageKB;
michael@0:     // Lock for safegarding the 64-bit sCurrentDecodedImageBytes
michael@0:     static PRLock *sAllocationLock;
michael@0:     static mozilla::Mutex* sNodeListMutex;
michael@0:     static Atomic<bool> sShutdown;
michael@0: };
michael@0: 
michael@0: } // namespace image
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif /* mozilla_imagelib_DiscardTracker_h_ */