using System;
using System.Threading;

namespace org.budnhead
{
	/**
	 * ConsumerProducerLock
	 * 
	 * Lock a Resource for one producer, mutliple consumers (read-only)
	 * 
	 * Producer Lock:			Producer will receive and hold lock if no other producer is active
	 * Producer Exclusive Lock:	Producer will receive and hold lock, while no consumers are active
	 * Consumer Lock:			Consumers will get lock while no Producer Exclusive Lock is held
	 * 
	 **/

	public class ConsumerProducerLock
	{
		Object		producer;
		Object		producerExclusiveLock;
		Object		consumerLock;

		Int32		consumers;

		bool		producerIsExclusive;

		public ConsumerProducerLock(){
			producer = new object();
			producerExclusiveLock = new object();
			consumerLock = new object();

			consumers = 0;
		}

		public void ConsumerEnter(){
			Monitor.Enter(producerExclusiveLock);
			Monitor.Enter(consumerLock);
			consumers ++;
			Monitor.Exit(consumerLock);
			Monitor.Exit(producerExclusiveLock);
		}
		public void ConsumerExit(){
			Monitor.Enter(producerExclusiveLock);
			Monitor.Enter(consumerLock);
			consumers --;
			if (consumers == 0){
				Monitor.Pulse(producerExclusiveLock);
			}
			Monitor.Exit(consumerLock);
			Monitor.Exit(producerExclusiveLock);
		}

		public void ProducerEnter(){
			Monitor.Enter(producer);
		}
		public void ProducerExit(){
			Monitor.Exit(producer);
			if (Monitor.IsEntered(producerExclusiveLock)){
				Monitor.Exit(producerExclusiveLock);
			}
		}

		public void producerExclusive(){
			Monitor.Enter(producerExclusiveLock);
			if (consumers > 0){
				Monitor.Wait(producerExclusiveLock);
			}
		}

	}
}