Revision 5c466d9ae581d1d2b276b873a7dd085729d6560e authored by Gregor Wagner on 31 January 2013, 01:17:07 UTC, committed by Gregor Wagner on 31 January 2013, 01:17:07 UTC
1 parent 187e38c
DiscardTracker.h
/* -*- 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/. */
#ifndef mozilla_imagelib_DiscardTracker_h_
#define mozilla_imagelib_DiscardTracker_h_
#include "mozilla/LinkedList.h"
#include "mozilla/TimeStamp.h"
class nsITimer;
namespace mozilla {
namespace image {
class RasterImage;
/**
* This static class maintains a linked list of RasterImage objects which are
* eligible for discarding.
*
* When Reset() is called, the node is removed from its position in the list
* (if it was there before) and appended to the beginnings of the list.
*
* Periodically (on a timer and when we notice that we're using more memory
* than we'd like for decoded images), we go through the list and discard
* decoded data from images at the end of the list.
*/
class DiscardTracker
{
public:
/**
* The DiscardTracker keeps a linked list of Node objects. Each object
* points to a RasterImage and contains a timestamp indicating when the
* node was inserted into the tracker.
*
* This structure is embedded within each RasterImage object, and we do
* |mDiscardTrackerNode.img = this| on RasterImage construction. Thus, a
* RasterImage must always call DiscardTracker::Remove() in its destructor
* to avoid having the tracker point to bogus memory.
*/
struct Node : public LinkedListElement<Node>
{
RasterImage *img;
TimeStamp timestamp;
};
/**
* Add an image to the front of the tracker's list, or move it to the front
* if it's already in the list. This function is main thread only.
*/
static nsresult Reset(struct Node* node);
/**
* Remove a node from the tracker; do nothing if the node is currently
* untracked. This function is main thread only.
*/
static void Remove(struct Node* node);
/**
* Initializes the discard tracker. This function is main thread only.
*/
static nsresult Initialize();
/**
* Shut the discard tracker down. This should be called on XPCOM shutdown
* so we destroy the discard timer's nsITimer. This function is main thread
* only.
*/
static void Shutdown();
/**
* Discard the decoded image data for all images tracked by the discard
* tracker. This function is main thread only.
*/
static void DiscardAll();
/**
* Inform the discard tracker that we've allocated or deallocated some
* memory for a decoded image. We use this to determine when we've
* allocated too much memory and should discard some images. This function
* can be called from any thread and is thread-safe.
*/
static void InformAllocation(int64_t bytes);
private:
/**
* This is called when the discard timer fires; it calls into DiscardNow().
*/
friend int DiscardTimeoutChangedCallback(const char* aPref, void *aClosure);
/**
* When run, this runnable sets sDiscardRunnablePending to false and calls
* DiscardNow().
*/
class DiscardRunnable : public nsRunnable
{
NS_IMETHOD Run();
};
static void ReloadTimeout();
static nsresult EnableTimer();
static void DisableTimer();
static void MaybeDiscardSoon();
static void TimerCallback(nsITimer *aTimer, void *aClosure);
static void DiscardNow();
static LinkedList<Node> sDiscardableImages;
static nsCOMPtr<nsITimer> sTimer;
static bool sInitialized;
static bool sTimerOn;
static int32_t sDiscardRunnablePending;
static int64_t sCurrentDecodedImageBytes;
static uint32_t sMinDiscardTimeoutMs;
static uint32_t sMaxDecodedImageKB;
// Lock for safegarding the 64-bit sCurrentDecodedImageBytes
static PRLock *sAllocationLock;
};
} // namespace image
} // namespace mozilla
#endif /* mozilla_imagelib_DiscardTracker_h_ */
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