1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/image/src/DiscardTracker.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,140 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this file,
1.7 + * You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef mozilla_imagelib_DiscardTracker_h_
1.10 +#define mozilla_imagelib_DiscardTracker_h_
1.11 +
1.12 +#include "mozilla/Atomics.h"
1.13 +#include "mozilla/LinkedList.h"
1.14 +#include "mozilla/Mutex.h"
1.15 +#include "mozilla/TimeStamp.h"
1.16 +#include "prlock.h"
1.17 +#include "nsThreadUtils.h"
1.18 +#include "nsAutoPtr.h"
1.19 +
1.20 +class nsITimer;
1.21 +
1.22 +namespace mozilla {
1.23 +namespace image {
1.24 +
1.25 +class RasterImage;
1.26 +
1.27 +/**
1.28 + * This static class maintains a linked list of RasterImage objects which are
1.29 + * eligible for discarding.
1.30 + *
1.31 + * When Reset() is called, the node is removed from its position in the list
1.32 + * (if it was there before) and appended to the beginnings of the list.
1.33 + *
1.34 + * Periodically (on a timer and when we notice that we're using more memory
1.35 + * than we'd like for decoded images), we go through the list and discard
1.36 + * decoded data from images at the end of the list.
1.37 + */
1.38 +class DiscardTracker
1.39 +{
1.40 + public:
1.41 + /**
1.42 + * The DiscardTracker keeps a linked list of Node objects. Each object
1.43 + * points to a RasterImage and contains a timestamp indicating when the
1.44 + * node was inserted into the tracker.
1.45 + *
1.46 + * This structure is embedded within each RasterImage object, and we do
1.47 + * |mDiscardTrackerNode.img = this| on RasterImage construction. Thus, a
1.48 + * RasterImage must always call DiscardTracker::Remove() in its destructor
1.49 + * to avoid having the tracker point to bogus memory.
1.50 + */
1.51 + struct Node : public LinkedListElement<Node>
1.52 + {
1.53 + RasterImage *img;
1.54 + TimeStamp timestamp;
1.55 + };
1.56 +
1.57 + /**
1.58 + * Add an image to the front of the tracker's list, or move it to the front
1.59 + * if it's already in the list. This function is main thread only.
1.60 + */
1.61 + static nsresult Reset(struct Node* node);
1.62 +
1.63 + /**
1.64 + * Remove a node from the tracker; do nothing if the node is currently
1.65 + * untracked. This function is main thread only.
1.66 + */
1.67 + static void Remove(struct Node* node);
1.68 +
1.69 + /**
1.70 + * Initializes the discard tracker. This function is main thread only.
1.71 + */
1.72 + static nsresult Initialize();
1.73 +
1.74 + /**
1.75 + * Shut the discard tracker down. This should be called on XPCOM shutdown
1.76 + * so we destroy the discard timer's nsITimer. This function is main thread
1.77 + * only.
1.78 + */
1.79 + static void Shutdown();
1.80 +
1.81 + /**
1.82 + * Discard the decoded image data for all images tracked by the discard
1.83 + * tracker. This function is main thread only.
1.84 + */
1.85 + static void DiscardAll();
1.86 +
1.87 + /**
1.88 + * Inform the discard tracker that we are going to allocate some memory
1.89 + * for a decoded image. We use this to determine when we've allocated
1.90 + * too much memory and should discard some images. This function can be
1.91 + * called from any thread and is thread-safe. If this function succeeds, the
1.92 + * caller is now responsible for ensuring that InformDeallocation is called.
1.93 + */
1.94 + static bool TryAllocation(uint64_t aBytes);
1.95 +
1.96 + /**
1.97 + * Inform the discard tracker that we've deallocated some memory for a
1.98 + * decoded image. This function can be called from any thread and is
1.99 + * thread-safe.
1.100 + */
1.101 + static void InformDeallocation(uint64_t aBytes);
1.102 +
1.103 + private:
1.104 + /**
1.105 + * This is called when the discard timer fires; it calls into DiscardNow().
1.106 + */
1.107 + friend void DiscardTimeoutChangedCallback(const char* aPref, void *aClosure);
1.108 +
1.109 + /**
1.110 + * When run, this runnable sets sDiscardRunnablePending to false and calls
1.111 + * DiscardNow().
1.112 + */
1.113 + class DiscardRunnable : public nsRunnable
1.114 + {
1.115 + NS_IMETHOD Run();
1.116 + };
1.117 +
1.118 + static void ReloadTimeout();
1.119 + static nsresult EnableTimer();
1.120 + static void DisableTimer();
1.121 + static void MaybeDiscardSoon();
1.122 + static void TimerCallback(nsITimer *aTimer, void *aClosure);
1.123 + static void DiscardNow();
1.124 +
1.125 + static LinkedList<Node> sDiscardableImages;
1.126 + static nsCOMPtr<nsITimer> sTimer;
1.127 + static bool sInitialized;
1.128 + static bool sTimerOn;
1.129 + static mozilla::Atomic<bool> sDiscardRunnablePending;
1.130 + static uint64_t sCurrentDecodedImageBytes;
1.131 + static uint32_t sMinDiscardTimeoutMs;
1.132 + static uint32_t sMaxDecodedImageKB;
1.133 + static uint32_t sHardLimitDecodedImageKB;
1.134 + // Lock for safegarding the 64-bit sCurrentDecodedImageBytes
1.135 + static PRLock *sAllocationLock;
1.136 + static mozilla::Mutex* sNodeListMutex;
1.137 + static Atomic<bool> sShutdown;
1.138 +};
1.139 +
1.140 +} // namespace image
1.141 +} // namespace mozilla
1.142 +
1.143 +#endif /* mozilla_imagelib_DiscardTracker_h_ */
