/*
* Copyright (c) 2009-2012 jMonkeyEngine
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * 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.
*
* * Neither the name of 'jMonkeyEngine' nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "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 THE COPYRIGHT OWNER 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.
*/
package com.jme3.asset.cache;
import com.jme3.asset.AssetKey;
import com.jme3.asset.CloneableSmartAsset;
import java.lang.ref.PhantomReference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.concurrent.ConcurrentHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* <code>WeakRefCloneAssetCache</code> caches cloneable assets in a weak-key
* cache, allowing them to be collected when memory is low.
* The cache stores weak references to the asset keys, so that
* when all clones of the original asset are collected, will cause the
* asset to be automatically removed from the cache.
*
* @author Kirill Vainer
*/
public class WeakRefCloneAssetCache implements AssetCache {
private static final Logger logger = Logger.getLogger(WeakRefAssetCache.class.getName());
private final ReferenceQueue<AssetKey> refQueue = new ReferenceQueue<AssetKey>();
/**
* Maps cloned key to AssetRef which has a weak ref to the original
* key and a strong ref to the original asset.
*/
private final ConcurrentHashMap<AssetKey, AssetRef> smartCache
= new ConcurrentHashMap<AssetKey, AssetRef>();
/**
* Stored in the ReferenceQueue to find out when originalKey is collected
* by GC. Once collected, the clonedKey is used to remove the asset
* from the cache.
*/
private static final class KeyRef extends PhantomReference<AssetKey> {
AssetKey clonedKey;
public KeyRef(AssetKey originalKey, ReferenceQueue<AssetKey> refQueue) {
super(originalKey, refQueue);
clonedKey = originalKey.clone();
}
}
/**
* Stores the original key and original asset.
* The asset info contains a cloneable asset (e.g. the original, from
* which all clones are made). Also a weak reference to the
* original key which is used when the clones are produced.
*/
private static final class AssetRef extends WeakReference<AssetKey> {
CloneableSmartAsset asset;
public AssetRef(CloneableSmartAsset originalAsset, AssetKey originalKey) {
super(originalKey);
this.asset = originalAsset;
}
}
private final ThreadLocal<ArrayList<AssetKey>> assetLoadStack
= new ThreadLocal<ArrayList<AssetKey>>() {
@Override
protected ArrayList<AssetKey> initialValue() {
return new ArrayList<AssetKey>();
}
};
private void removeCollectedAssets(){
int removedAssets = 0;
for (KeyRef ref; (ref = (KeyRef)refQueue.poll()) != null;){
// (Cannot use ref.get() since it was just collected by GC!)
AssetKey key = ref.clonedKey;
// Asset was collected, note that at this point the asset cache
// might not even have this asset anymore, it is OK.
if (smartCache.remove(key) != null){
removedAssets ++;
//System.out.println("WeakRefAssetCache: The asset " + ref.assetKey + " was purged from the cache");
}
}
if (removedAssets >= 1) {
logger.log(Level.FINE, "WeakRefAssetCache: {0} assets were purged from the cache.", removedAssets);
}
}
public <T> void addToCache(AssetKey<T> originalKey, T obj) {
// Make room for new asset
removeCollectedAssets();
CloneableSmartAsset asset = (CloneableSmartAsset) obj;
// No circular references, since the original asset is
// strongly referenced, we don't want the key strongly referenced.
asset.setKey(null);
// Start tracking the collection of originalKey
// (this adds the KeyRef to the ReferenceQueue)
KeyRef ref = new KeyRef(originalKey, refQueue);
// Place the asset in the cache, but use a clone of
// the original key.
smartCache.put(ref.clonedKey, new AssetRef(asset, originalKey));
// Push the original key used to load the asset
// so that it can be set on the clone later
ArrayList<AssetKey> loadStack = assetLoadStack.get();
loadStack.add(originalKey);
}
public <T> void registerAssetClone(AssetKey<T> key, T clone) {
ArrayList<AssetKey> loadStack = assetLoadStack.get();
((CloneableSmartAsset)clone).setKey(loadStack.remove(loadStack.size() - 1));
}
public void notifyNoAssetClone() {
ArrayList<AssetKey> loadStack = assetLoadStack.get();
loadStack.remove(loadStack.size() - 1);
}
public <T> T getFromCache(AssetKey<T> key) {
AssetRef smartInfo = smartCache.get(key);
if (smartInfo == null) {
return null;
} else {
// NOTE: Optimization so that registerAssetClone()
// can check this and determine that the asset clone
// belongs to the asset retrieved here.
AssetKey keyForTheClone = smartInfo.get();
if (keyForTheClone == null){
// The asset was JUST collected by GC
// (between here and smartCache.get)
return null;
}
// Prevent original key from getting collected
// while an asset is loaded for it.
ArrayList<AssetKey> loadStack = assetLoadStack.get();
loadStack.add(keyForTheClone);
return (T) smartInfo.asset;
}
}
public boolean deleteFromCache(AssetKey key) {
ArrayList<AssetKey> loadStack = assetLoadStack.get();
if (!loadStack.isEmpty()){
throw new UnsupportedOperationException("Cache cannot be modified"
+ "while assets are being loaded");
}
return smartCache.remove(key) != null;
}
public void clearCache() {
ArrayList<AssetKey> loadStack = assetLoadStack.get();
if (!loadStack.isEmpty()){
throw new UnsupportedOperationException("Cache cannot be modified"
+ "while assets are being loaded");
}
smartCache.clear();
}
}