mono/mcs/class/System.Threading.Tasks.Dataflow/System.Threading.Tasks.Dataflow/BroadcastBlock.cs

// BroadcastBlock.cs
//
// Copyright (c) 2011 Jérémie "garuma" Laval
//
// 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.
//
//

using System.Collections.Generic;
using System.Collections.Concurrent;

namespace System.Threading.Tasks.Dataflow {
	public sealed class BroadcastBlock<T> : IPropagatorBlock<T, T>, IReceivableSourceBlock<T> {
		static readonly DataflowBlockOptions defaultOptions = new DataflowBlockOptions ();

		readonly CompletionHelper compHelper;
		readonly BlockingCollection<T> messageQueue = new BlockingCollection<T> ();
		readonly MessageBox<T> messageBox;
		readonly MessageVault<T> vault;
		readonly DataflowBlockOptions dataflowBlockOptions;
		readonly Func<T, T> cloner;
		readonly MessageOutgoingQueue<T> outgoing;
		readonly TargetBuffer<T> targets = new TargetBuffer<T> ();
		DataflowMessageHeader headers = DataflowMessageHeader.NewValid ();

		public BroadcastBlock (Func<T, T> cloner) : this (cloner, defaultOptions)
		{

		}

		public BroadcastBlock (Func<T, T> cloner, DataflowBlockOptions dataflowBlockOptions)
		{
			if (dataflowBlockOptions == null)
				throw new ArgumentNullException ("dataflowBlockOptions");

			this.cloner = cloner;
			this.dataflowBlockOptions = dataflowBlockOptions;
			this.compHelper = CompletionHelper.GetNew (dataflowBlockOptions);
			this.messageBox = new PassingMessageBox<T> (this, messageQueue, compHelper,
				() => outgoing.IsCompleted, BroadcastProcess, dataflowBlockOptions);
			this.outgoing = new MessageOutgoingQueue<T> (this, compHelper,
				() => messageQueue.IsCompleted, () => messageBox.DecreaseCount (),
				dataflowBlockOptions);
			this.vault = new MessageVault<T> ();
		}

		public DataflowMessageStatus OfferMessage (DataflowMessageHeader messageHeader,
		                                           T messageValue,
		                                           ISourceBlock<T> source,
		                                           bool consumeToAccept)
		{
			return messageBox.OfferMessage (messageHeader, messageValue, source, consumeToAccept);
		}

		public IDisposable LinkTo (ITargetBlock<T> target, DataflowLinkOptions linkOptions)
		{
			return targets.AddTarget (target, false); // TODO
		}

		public T ConsumeMessage (DataflowMessageHeader messageHeader, ITargetBlock<T> target, out bool messageConsumed)
		{
			return cloner(vault.ConsumeMessage (messageHeader, target, out messageConsumed));
		}

		public void ReleaseReservation (DataflowMessageHeader messageHeader, ITargetBlock<T> target)
		{
			vault.ReleaseReservation (messageHeader, target);
		}

		public bool ReserveMessage (DataflowMessageHeader messageHeader, ITargetBlock<T> target)
		{
			return vault.ReserveMessage (messageHeader, target);
		}

		public bool TryReceive (Predicate<T> filter, out T item)
		{
			return outgoing.TryReceive (filter, out item);
		}

		public bool TryReceiveAll (out IList<T> items)
		{
			return outgoing.TryReceiveAll (out items);
		}

		void BroadcastProcess ()
		{
			T input;

			if (!messageQueue.TryTake (out input) || targets.Current == null)
				return;

			foreach (var target in targets) {
				DataflowMessageHeader header = headers.Increment ();
				if (cloner != null)
					vault.StoreMessage (header, input);
				target.OfferMessage (header, input, this, cloner != null);
				// TODO: verify if it's the correct semantic
				T save = input;
				if (!messageQueue.TryTake (out input))
					input = save;
			}
		}

		public void Complete ()
		{
			messageBox.Complete ();
		}

		public void Fault (Exception ex)
		{
			compHelper.RequestFault (ex);
		}

		public Task Completion {
			get {
				return compHelper.Completion;
			}
		}

		public override string ToString ()
		{
			return NameHelper.GetName (this, dataflowBlockOptions);
		}
	}
}