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/*
* Copyright (C) 2012 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "LayerPool.h"
#include "Logging.h"
#include "WebTileLayer.h"
#include <wtf/CurrentTime.h>
namespace WebCore {
static const double capacityDecayTime = 5;
LayerPool::LayerPool()
: m_totalBytes(0)
, m_maxBytesForPool(48 * 1024 * 1024)
, m_pruneTimer(this, &LayerPool::pruneTimerFired)
, m_lastAddTime(0)
{
}
LayerPool* LayerPool::sharedPool()
{
static LayerPool* sharedPool = new LayerPool;
return sharedPool;
}
unsigned LayerPool::backingStoreBytesForSize(const IntSize& size)
{
return size.width() * size.height() * 4;
}
LayerPool::LayerList& LayerPool::listOfLayersWithSize(const IntSize& size, AccessType accessType)
{
HashMap<IntSize, LayerList>::iterator it = m_reuseLists.find(size);
if (it == m_reuseLists.end()) {
it = m_reuseLists.add(size, LayerList()).iterator;
m_sizesInPruneOrder.append(size);
} else if (accessType == MarkAsUsed) {
m_sizesInPruneOrder.remove(m_sizesInPruneOrder.reverseFind(size));
m_sizesInPruneOrder.append(size);
}
return it->value;
}
void LayerPool::addLayer(const RetainPtr<WebTileLayer>& layer)
{
IntSize layerSize([layer.get() bounds].size);
if (!canReuseLayerWithSize(layerSize))
return;
listOfLayersWithSize(layerSize).prepend(layer);
m_totalBytes += backingStoreBytesForSize(layerSize);
m_lastAddTime = currentTime();
schedulePrune();
}
RetainPtr<WebTileLayer> LayerPool::takeLayerWithSize(const IntSize& size)
{
if (!canReuseLayerWithSize(size))
return nil;
LayerList& reuseList = listOfLayersWithSize(size, MarkAsUsed);
if (reuseList.isEmpty())
return nil;
m_totalBytes -= backingStoreBytesForSize(size);
return reuseList.takeFirst();
}
unsigned LayerPool::decayedCapacity() const
{
// Decay to one quarter over capacityDecayTime
double timeSinceLastAdd = currentTime() - m_lastAddTime;
if (timeSinceLastAdd > capacityDecayTime)
return m_maxBytesForPool / 4;
float decayProgess = float(timeSinceLastAdd / capacityDecayTime);
return m_maxBytesForPool / 4 + m_maxBytesForPool * 3 / 4 * (1 - decayProgess);
}
void LayerPool::schedulePrune()
{
if (m_pruneTimer.isActive())
return;
m_pruneTimer.startOneShot(1);
}
void LayerPool::pruneTimerFired(Timer<LayerPool>*)
{
unsigned shrinkTo = decayedCapacity();
while (m_totalBytes > shrinkTo) {
ASSERT(!m_sizesInPruneOrder.isEmpty());
IntSize sizeToDrop = m_sizesInPruneOrder.first();
LayerList& oldestReuseList = m_reuseLists.find(sizeToDrop)->value;
if (oldestReuseList.isEmpty()) {
m_reuseLists.remove(sizeToDrop);
m_sizesInPruneOrder.remove(0);
continue;
}
m_totalBytes -= backingStoreBytesForSize(sizeToDrop);
// The last element in the list is the oldest, hence most likely not to
// still have a backing store.
oldestReuseList.remove(--oldestReuseList.end());
}
if (currentTime() - m_lastAddTime <= capacityDecayTime)
schedulePrune();
}
void LayerPool::drain()
{
m_reuseLists.clear();
m_sizesInPruneOrder.clear();
m_totalBytes = 0;
}
}
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