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Ehcache is an open source, standards-based cache used to boost performance, offload the database and simplify scalability. Ehcache is robust, proven and full-featured and this has made it the most widely-used Java-based cache.

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/**
 *  Copyright Terracotta, Inc.
 *
 *  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 net.sf.ehcache.concurrent;

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

/**
 * A simple ReadWriteLock synchronizer.
 *
 * @author Alex Snaps
 */
public class ReadWriteLockSync implements Sync {

    private final ReentrantReadWriteLock rrwl;

    /**
     * default constructor.
     */
    public ReadWriteLockSync() {
        this(new ReentrantReadWriteLock());
    }

    /**
     * Constructor.
     * @param lock
     */
    public ReadWriteLockSync(ReentrantReadWriteLock lock) {
        this.rrwl = lock;
    }
    /**
     * {@inheritDoc}
     */
    public void lock(final LockType type) {
        getLock(type).lock();
    }

    /**
     * {@inheritDoc}
     */
    public boolean tryLock(final LockType type, final long msec) throws InterruptedException {
        return getLock(type).tryLock(msec, TimeUnit.MILLISECONDS);
    }

    /**
     * {@inheritDoc}
     */
    public void unlock(final LockType type) {
        getLock(type).unlock();
    }

    private Lock getLock(final LockType type) {
        switch (type) {
            case READ:
                return rrwl.readLock();
            case WRITE:
                return rrwl.writeLock();
            default:
                throw new IllegalArgumentException("We don't support any other lock type than READ or WRITE!");
        }
    }

    /**
     * Gets the {@code ReadWriteLock} backing this sync.
     * 
     * @return the backing {@code ReadWriteLock}
     */
    public ReadWriteLock getReadWriteLock() {
      return rrwl;
    }
    
    /**
     * {@inheritDoc}
     */
    public boolean isHeldByCurrentThread(LockType type) {
        switch (type) {
            case READ:
                throw new UnsupportedOperationException("Querying of read lock is not supported.");
            case WRITE:
                return rrwl.isWriteLockedByCurrentThread();
            default:
                throw new IllegalArgumentException("We don't support any other lock type than READ or WRITE!");
        }
    }
}