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/* 
 * Copyright 2015 Terracotta, Inc., a Software AG company.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.terracotta.offheapstore;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.terracotta.offheapstore.paging.PageSource;
import org.terracotta.offheapstore.storage.StorageEngine;

/**
 * A concurrent-read, exclusive-write off-heap clock cache.
 * 

* This cache uses one of the unused bits in the off-heap entry's status value to * store the clock data. This clock data is racily to updated during read * operations. Since clock eviction data resides in the hash-map's table, it is * correctly copied across during table resize operations. *

* The cache uses a regular {@code ReentrantReadWriteLock} to provide read/write * exclusion/sharing properties. * * @param the type of keys maintained by this map * @param the type of mapped values * * @author Chris Dennis */ public class ReadWriteLockedOffHeapClockCache extends AbstractOffHeapClockCache { private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true); public ReadWriteLockedOffHeapClockCache(PageSource source, StorageEngine storageEngine) { super(source, storageEngine); } public ReadWriteLockedOffHeapClockCache(PageSource source, boolean tableAllocationsSteal, StorageEngine storageEngine) { super(source, tableAllocationsSteal, storageEngine); } public ReadWriteLockedOffHeapClockCache(PageSource source, StorageEngine storageEngine, int tableSize) { super(source, storageEngine, tableSize); } public ReadWriteLockedOffHeapClockCache(PageSource source, boolean tableAllocationsSteal, StorageEngine storageEngine, int tableSize) { super(source, tableAllocationsSteal, storageEngine, tableSize); } @Override public Lock readLock() { return lock.readLock(); } @Override public Lock writeLock() { return lock.writeLock(); } @Override public ReentrantReadWriteLock getLock() { return lock; } }





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