/source/library/Interlace/ReactorUtilities/BlockingThreadInvoker.cs

#region Using Directives and Copyright Notice



// Copyright (c) 2007-2010, Computer Consultancy Pty Ltd

// All rights reserved.

// 

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//     * Redistributions of source code must retain the above copyright

//       notice, this list of conditions and the following disclaimer.

//     * Redistributions in binary form must reproduce the above copyright

//       notice, this list of conditions and the following disclaimer in the

//       documentation and/or other materials provided with the distribution.

//     * Neither the name of the Computer Consultancy Pty Ltd nor the

//       names of its contributors may be used to endorse or promote products

//       derived from this software without specific prior written permission.

// 

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 

// ARE DISCLAIMED. IN NO EVENT SHALL COMPUTER CONSULTANCY PTY LTD BE LIABLE 

// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 

// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 

// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 

// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 

// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 

// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH

// DAMAGE.



using System;

using System.Collections.Generic;

using System.Text;

using System.Threading;

using System.Windows.Forms;



using Interlace.ReactorCore;

using Interlace.Utilities;



#endregion



namespace Interlace.ReactorUtilities

{

    /// <summary>

    /// An <see cref="IThreadInvoker"/> implementation that blocks. Great care should be taken

    /// when using this class; see the remarks.

    /// </summary>

    /// <remarks>

    /// This class should only be used for testing. There are a number of traps when using it.

    /// First, if the called method needs a running UI thread or reactor thread, a deadlock will 

    /// most likely occur. Also, the callbacks will fail as soon as this object is disposed, which

    /// may be too soon.

    /// </remarks>

    public class BlockingThreadInvoker : IDisposable, IThreadInvoker

    {

        AutoResetEvent _requestSignal;

        AutoResetEvent _responseSignal;



        object _requestLock = new object();

        Delegate _requestDelegate = null;

        object[] _requestArguments = null;



        object _responseResult = null;



        bool _disposed = false;



        public BlockingThreadInvoker()

        {

            _requestSignal = new AutoResetEvent(false);

            _responseSignal = new AutoResetEvent(false);

        }



        public void Dispose()

        {

            lock (_requestLock)

            {

                _disposed = true;

            }



            if (_requestSignal != null)

            {

                _requestSignal.Close();

                _requestSignal = null;

            }



            if (_responseSignal != null)

            {

                _responseSignal.Close();

                _responseSignal = null;

            }

        }



        object WaitOnInternal(DeferredObject deferred)

        {

            object result = null;

            Exception exception = null;

            bool completed = false;



            deferred.ObjectCompletion(

                delegate(object deferredResult)

                {

                    result = deferredResult;

                    completed = true;



                    return null;

                },

                delegate(DeferredFailure failure)

                {

                    exception = failure.Exception;

                    completed = true;



                    return null;

                }, null);



            while (!completed)

            {

                _requestSignal.WaitOne();



                _responseResult = _requestDelegate.DynamicInvoke(_requestArguments);



                _requestDelegate = null;

                _requestArguments = null;



                _responseSignal.Set();

            }



            if (exception != null)

            {

                throw new ApplicationException(

                    "An exception was thrown while running callbacks. Check InnerException for details.", exception);

            }



            return result;

        }



        public void WaitOn(VoidDeferred deferred)

        {

            WaitOnInternal(deferred);

        }



        public T WaitOn<T>(Deferred<T> deferred)

        {

            return (T)WaitOnInternal(deferred);

        }



        #region IThreadInvoker Members



        public object Invoke(Delegate method)

        {

            return Invoke(method, new object[] { });

        }



        public object Invoke(Delegate method, params object[] args)

        {

            lock (_requestLock)

            {

                if (_disposed) throw new InvalidOperationException(

                    "The blocking thread invoker has been disposed; invokes should not be made.");



                _requestDelegate = method;

                _requestArguments = args;



                _requestSignal.Set();



                _responseSignal.WaitOne();



                object result = _responseResult;

                _responseResult = null;



                return result;

            }

        }



        #endregion

    }

}