/* 
 * Copyright (c) 2006 Stiftung Deutsches Elektronen-Synchroton, 
 * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY.
 *
 * THIS SOFTWARE IS PROVIDED UNDER THIS LICENSE ON AN "../AS IS" BASIS. 
 * WITHOUT WARRANTY OF ANY KIND, EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED 
 * TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR PARTICULAR PURPOSE AND 
 * NON-INFRINGEMENT. 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. SHOULD THE SOFTWARE PROVE DEFECTIVE 
 * IN ANY RESPECT, THE USER ASSUMES THE COST OF ANY NECESSARY SERVICING, REPAIR OR 
 * CORRECTION. THIS DISCLAIMER OF WARRANTY CONSTITUTES AN ESSENTIAL PART OF THIS LICENSE. 
 * NO USE OF ANY SOFTWARE IS AUTHORIZED HEREUNDER EXCEPT UNDER THIS DISCLAIMER.
 * DESY HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, 
 * OR MODIFICATIONS.
 * THE FULL LICENSE SPECIFYING FOR THE SOFTWARE THE REDISTRIBUTION, MODIFICATION, 
 * USAGE AND OTHER RIGHTS AND OBLIGATIONS IS INCLUDED WITH THE DISTRIBUTION OF THIS 
 * PROJECT IN THE FILE LICENSE.HTML. IF THE LICENSE IS NOT INCLUDED YOU MAY FIND A COPY 
 * AT HTTP://WWW.DESY.DE/LEGAL/LICENSE.HTM
 */
package org.csstudio.platform.internal.simpledal.local;

import java.util.concurrent.ConcurrentHashMap;
import org.csstudio.platform.model.pvs.IProcessVariableAddress;
import org.csstudio.platform.model.pvs.ValueType;

public final class LocalChannelPool {
	/**
	 * Contains all active channels.
	 */
	private ConcurrentHashMap<IProcessVariableAddress, LocalChannel> _channels;

	/**
	 * The singleton instance.
	 */
	private static LocalChannelPool _instance;

	/**
	 * Constructor.
	 */
	private LocalChannelPool() {
		_channels = new ConcurrentHashMap<IProcessVariableAddress, LocalChannel>();
	}

	/**
	 * Gets the singleton instance.
	 * 
	 * @return the singleton instance
	 */
	public static synchronized LocalChannelPool getInstance() {
		if (_instance == null) {
			_instance = new LocalChannelPool();
		}

		return _instance;
	}

	/**
	 * {@inheritDoc}
	 */
	public synchronized LocalChannel getChannel(
			final IProcessVariableAddress processVariable, ValueType valueType) {
		assert processVariable != null;

		LocalChannel channel = _channels.get(processVariable);

		if (channel == null) {
			channel = new LocalChannel(processVariable);
			_channels.put(processVariable, channel);
		}

		return channel;
	}
}