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/*
* The MIT License
*
* Copyright (c) 2009 The Broad Institute
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package htsjdk.samtools.util;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* LRU collection class for managing objects that place some resource burden such that not too many of them
* can existing in the VM at one time, but they can be reconstructed ias necessary.
* Original motivation was for an LRU cache of FileOutputStreams.
*
* @author [email protected]
*/
public class ResourceLimitedMap {
private static final float hashTableLoadFactor = 0.75f;
private final LinkedHashMap map;
private final int cacheSize;
private final ResourceLimitedMapFunctor functor;
/**
* Create LRU cache
* @param cacheSize Max number of objects to be stored in the cache.
* @param functor Encapsulates methods for creating a new object if it isn't in the cache, and
* for finalizing an object that is getting LRU'ed out of the cache.
*/
public ResourceLimitedMap(final int cacheSize, final ResourceLimitedMapFunctor functor) {
this.cacheSize = cacheSize;
this.functor = functor;
// Make hash table big enough so that it never gets resized.
final int hashTableCapacity = (int)Math.ceil(cacheSize / hashTableLoadFactor) + 1;
// Created LinkedHashMap in LRU mode
map = new LinkedHashMap(hashTableCapacity, hashTableLoadFactor, true) {
@Override protected boolean removeEldestEntry (final Map.Entry eldest) {
if (size() > ResourceLimitedMap.this.cacheSize) {
ResourceLimitedMap.this.functor.finalizeValue(eldest.getKey(), eldest.getValue());
return true;
} else {
return false;
}
}
};
}
/**
* Return an existing value, or create a new one if necessary. If creating a new one and the
* cache is full, the eldest object is pushed out of the cache.
* @param key Key of desired value.
* @return Either existing value, or new value created from key and inserted into map.
*/
public Value get(final Key key) {
if (!map.containsKey(key)) {
map.put(key, functor.makeValue(key));
}
return map.get(key);
}
public Value remove(final Key key) {
return map.remove(key);
}
/**
* Determine if the map contains the given key. Note that even if the map does not contain
* the key, get(key) will return a value, because one will be created.
* @param key
* @return true if the map currently contains the given key. It is unknown whether the map
* may have contained the key in the past.
*/
public boolean containsKey(final Key key) {
return map.containsKey(key);
}
/**
* Remove all the values from the map, and call functory.finalizeValue() on each of them.
*/
public void finalizeAll() {
for (final Map.Entry entry : map.entrySet()) {
functor.finalizeValue(entry.getKey(), entry.getValue());
}
map.clear();
}
}
