AsyncResultNoResult.cs :  » Business-Application » 32feet.NET » InTheHand » Net » C# / CSharp Open Source

/******************************************************************************
Module:  AsyncResultNoResult.cs
Notices: Written by Jeffrey Richter
******************************************************************************/

using System;
using System.Threading;
using System.Diagnostics;


///////////////////////////////////////////////////////////////////////////////
namespace InTheHand.Net{

    //[DebuggerNonUserCode] // alanjmcf
    internal class AsyncResultNoResult : IAsyncResult
    {
       // Fields set at construction which never change while operation is pending
       private readonly AsyncCallback m_AsyncCallback;
       private readonly Object m_AsyncState;

       // Field set at construction which do change after operation completes
       private const Int32 c_StatePending = 0;
       private const Int32 c_StateCompletedSynchronously = 1;
       private const Int32 c_StateCompletedAsynchronously = 2;
       private Int32 m_CompletedState = c_StatePending;

       // Field that may or may not get set depending on usage
       private ManualResetEvent m_AsyncWaitHandle;

       // Fields set when operation completes
       private Exception m_exception;

       public AsyncResultNoResult(AsyncCallback asyncCallback, Object state)
       {
          m_AsyncCallback = asyncCallback;
          m_AsyncState = state;
       }

       //[DebuggerNonUserCode] // alanjmcf
       //[Obsolete("temp Call with: Boolean callbackOnNewThread")]
       public void SetAsCompleted(Exception exception, Boolean completedSynchronously)
       {
          AsyncResultCompletion x;
          if (completedSynchronously) x = AsyncResultCompletion.IsSync;
          else x = AsyncResultCompletion.IsAsync;
          SetAsCompleted(exception, x);
       }

       //[DebuggerStepThrough] // alanjmcf
       public void SetAsCompleted(Exception exception, AsyncResultCompletion completion)
       {
          bool completedSynchronously = completion == AsyncResultCompletion.IsSync;
          // Passing null for exception means no error occurred; this is the common case
          m_exception = exception;

          // The m_CompletedState field MUST be set prior calling the callback
          Int32 prevState = Interlocked.Exchange(ref m_CompletedState,
             completedSynchronously ? c_StateCompletedSynchronously : c_StateCompletedAsynchronously);
          if (prevState != c_StatePending)
             throw new InvalidOperationException("You can set a result only once");

          // If the event exists, set it
          if (m_AsyncWaitHandle != null) m_AsyncWaitHandle.Set();

          // If a callback method was set, call it
          if (m_AsyncCallback != null) {
             if (completion != AsyncResultCompletion.MakeAsync)
                 m_AsyncCallback(this);
             else
                ThreadPool.QueueUserWorkItem(CallbackRunner);
          }
       }

       void CallbackRunner(object state)
       {
           m_AsyncCallback(this);
       }

       [DebuggerNonUserCode] // alanjmcf
       public void EndInvoke()
       {
          // This method assumes that only 1 thread calls EndInvoke for this object
          if (!IsCompleted)
          {
             // If the operation isn't done, wait for it
             AsyncWaitHandle.WaitOne();
             AsyncWaitHandle.Close();
             m_AsyncWaitHandle = null;  // Allow early GC
          }

          // Operation is done: if an exception occured, throw it
          if (m_exception != null) throw m_exception;
       }

       #region Implementation of IAsyncResult
       public Object AsyncState { get { return m_AsyncState; } }

       public Boolean CompletedSynchronously
       {
          get { return m_CompletedState == c_StateCompletedSynchronously; }
       }

       public WaitHandle AsyncWaitHandle
       {
          get
          {
             if (m_AsyncWaitHandle == null)
             {
                Boolean done = IsCompleted;
                ManualResetEvent mre = new ManualResetEvent(done);
                if (Interlocked.CompareExchange(ref m_AsyncWaitHandle, mre, null) != null)
                {
                   // Another thread created this object's event; dispose the event we just created
                   mre.Close();
                }
                else
                {
                   if (!done && IsCompleted)
                   {
                      // If the operation wasn't done when we created 
                      // the event but now it is done, set the event
                      m_AsyncWaitHandle.Set();
                   }
                }
             }
             return m_AsyncWaitHandle;
          }
       }

       public Boolean IsCompleted
       {
          get { return m_CompletedState != c_StatePending; }
       }
       #endregion
    }


    // alanjmcf
    [DebuggerNonUserCode] // alanjmcf
    internal class AsyncNoResult<TParams> : AsyncResultNoResult
    {
        TParams m_args;

        public AsyncNoResult(AsyncCallback asyncCallback, Object state, TParams args)
            : base(asyncCallback, state)
        {
            m_args = args;
        }

        public TParams BeginParameters { get { return m_args; } }
    }

}
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