1 files changed, 1002 insertions, 0 deletions

diff --git a/ThirdParty/SmartThreadPool/WorkItem.cs b/ThirdParty/SmartThreadPool/WorkItem.cs
new file mode 100644
index 0000000..edb8ac0
--- /dev/null
+++ b/ThirdParty/SmartThreadPool/WorkItem.cs
@@ -0,0 +1,1002 @@
+using System;
+using System.Threading;
+using System.Diagnostics;
+
+namespace Amib.Threading.Internal
+{
+    /// <summary>
+    /// Holds a callback delegate and the state for that delegate.
+    /// </summary>
+    public partial class WorkItem : IHasWorkItemPriority
+    {
+        #region WorkItemState enum
+
+        /// <summary>
+        /// Indicates the state of the work item in the thread pool
+        /// </summary>
+        private enum WorkItemState
+        {
+            InQueue = 0,    // Nexts: InProgress, Canceled
+            InProgress = 1,    // Nexts: Completed, Canceled
+            Completed = 2,    // Stays Completed
+            Canceled = 3,    // Stays Canceled
+        }
+
+        private static bool IsValidStatesTransition(WorkItemState currentState, WorkItemState nextState)
+        {
+            bool valid = false;
+
+            switch (currentState)
+            {
+                case WorkItemState.InQueue:
+                    valid = (WorkItemState.InProgress == nextState) || (WorkItemState.Canceled == nextState);
+                    break;
+                case WorkItemState.InProgress:
+                    valid = (WorkItemState.Completed == nextState) || (WorkItemState.Canceled == nextState);
+                    break;
+                case WorkItemState.Completed:
+                case WorkItemState.Canceled:
+                    // Cannot be changed
+                    break;
+                default:
+                    // Unknown state
+                    Debug.Assert(false);
+                    break;
+            }
+
+            return valid;
+        }
+
+        #endregion
+
+        #region Fields
+
+        /// <summary>
+        /// Callback delegate for the callback.
+        /// </summary>
+        private readonly WorkItemCallback _callback;
+
+        /// <summary>
+        /// State with which to call the callback delegate.
+        /// </summary>
+        private object _state;
+
+#if !(_WINDOWS_CE) && !(_SILVERLIGHT) && !(WINDOWS_PHONE)
+        /// <summary>
+        /// Stores the caller's context
+        /// </summary>
+        private readonly CallerThreadContext _callerContext;
+#endif
+        /// <summary>
+        /// Holds the result of the mehtod
+        /// </summary>
+        private object _result;
+
+        /// <summary>
+        /// Hold the exception if the method threw it
+        /// </summary>
+        private Exception _exception;
+
+        /// <summary>
+        /// Hold the state of the work item
+        /// </summary>
+        private WorkItemState _workItemState;
+
+        /// <summary>
+        /// A ManualResetEvent to indicate that the result is ready
+        /// </summary>
+        private ManualResetEvent _workItemCompleted;
+
+        /// <summary>
+        /// A reference count to the _workItemCompleted.
+        /// When it reaches to zero _workItemCompleted is Closed
+        /// </summary>
+        private int _workItemCompletedRefCount;
+
+        /// <summary>
+        /// Represents the result state of the work item
+        /// </summary>
+        private readonly WorkItemResult _workItemResult;
+
+        /// <summary>
+        /// Work item info
+        /// </summary>
+        private readonly WorkItemInfo _workItemInfo;
+
+        /// <summary>
+        /// Called when the WorkItem starts
+        /// </summary>
+        private event WorkItemStateCallback _workItemStartedEvent;
+
+        /// <summary>
+        /// Called when the WorkItem completes
+        /// </summary>
+        private event WorkItemStateCallback _workItemCompletedEvent;
+
+        /// <summary>
+        /// A reference to an object that indicates whatever the
+        /// WorkItemsGroup has been canceled
+        /// </summary>
+        private CanceledWorkItemsGroup _canceledWorkItemsGroup = CanceledWorkItemsGroup.NotCanceledWorkItemsGroup;
+
+        /// <summary>
+        /// A reference to an object that indicates whatever the
+        /// SmartThreadPool has been canceled
+        /// </summary>
+        private CanceledWorkItemsGroup _canceledSmartThreadPool = CanceledWorkItemsGroup.NotCanceledWorkItemsGroup;
+
+        /// <summary>
+        /// The work item group this work item belong to.
+        /// </summary>
+        private readonly IWorkItemsGroup _workItemsGroup;
+
+        /// <summary>
+        /// The thread that executes this workitem.
+        /// This field is available for the period when the work item is executed, before and after it is null.
+        /// </summary>
+        private Thread _executingThread;
+
+        /// <summary>
+        /// The absulote time when the work item will be timeout
+        /// </summary>
+        private long _expirationTime;
+
+        #region Performance Counter fields
+
+
+
+
+        /// <summary>
+        /// Stores how long the work item waited on the stp queue
+        /// </summary>
+        private Stopwatch _waitingOnQueueStopwatch;
+
+        /// <summary>
+        /// Stores how much time it took the work item to execute after it went out of the queue
+        /// </summary>
+        private Stopwatch _processingStopwatch;
+
+        #endregion
+
+        #endregion
+
+        #region Properties
+
+        public TimeSpan WaitingTime
+        {
+            get
+            {
+                return _waitingOnQueueStopwatch.Elapsed;
+            }
+        }
+
+        public TimeSpan ProcessTime
+        {
+            get
+            {
+                return _processingStopwatch.Elapsed;
+            }
+        }
+
+        internal WorkItemInfo WorkItemInfo
+        {
+            get
+            {
+                return _workItemInfo;
+            }
+        }
+
+        #endregion
+
+        #region Construction
+
+        /// <summary>
+        /// Initialize the callback holding object.
+        /// </summary>
+        /// <param name="workItemsGroup">The workItemGroup of the workitem</param>
+        /// <param name="workItemInfo">The WorkItemInfo of te workitem</param>
+        /// <param name="callback">Callback delegate for the callback.</param>
+        /// <param name="state">State with which to call the callback delegate.</param>
+        ///
+        /// We assume that the WorkItem object is created within the thread
+        /// that meant to run the callback
+        public WorkItem(
+            IWorkItemsGroup workItemsGroup,
+            WorkItemInfo workItemInfo,
+            WorkItemCallback callback,
+            object state)
+        {
+            _workItemsGroup = workItemsGroup;
+            _workItemInfo = workItemInfo;
+
+#if !(_WINDOWS_CE) && !(_SILVERLIGHT) && !(WINDOWS_PHONE)
+            if (_workItemInfo.UseCallerCallContext || _workItemInfo.UseCallerHttpContext)
+            {
+                _callerContext = CallerThreadContext.Capture(_workItemInfo.UseCallerCallContext, _workItemInfo.UseCallerHttpContext);
+            }
+#endif
+
+            _callback = callback;
+            _state = state;
+            _workItemResult = new WorkItemResult(this);
+            Initialize();
+        }
+
+        internal void Initialize()
+        {
+            // The _workItemState is changed directly instead of using the SetWorkItemState
+            // method since we don't want to go throught IsValidStateTransition.
+            _workItemState = WorkItemState.InQueue;
+
+            _workItemCompleted = null;
+            _workItemCompletedRefCount = 0;
+            _waitingOnQueueStopwatch = new Stopwatch();
+            _processingStopwatch = new Stopwatch();
+            _expirationTime =
+                _workItemInfo.Timeout > 0 ?
+                DateTime.UtcNow.Ticks + _workItemInfo.Timeout * TimeSpan.TicksPerMillisecond :
+                long.MaxValue;
+        }
+
+        internal bool WasQueuedBy(IWorkItemsGroup workItemsGroup)
+        {
+            return (workItemsGroup == _workItemsGroup);
+        }
+
+
+        #endregion
+
+        #region Methods
+
+        internal CanceledWorkItemsGroup CanceledWorkItemsGroup
+        {
+            get { return _canceledWorkItemsGroup; }
+            set { _canceledWorkItemsGroup = value; }
+        }
+
+        internal CanceledWorkItemsGroup CanceledSmartThreadPool
+        {
+            get { return _canceledSmartThreadPool; }
+            set { _canceledSmartThreadPool = value; }
+        }
+
+        /// <summary>
+        /// Change the state of the work item to in progress if it wasn't canceled.
+        /// </summary>
+        /// <returns>
+        /// Return true on success or false in case the work item was canceled.
+        /// If the work item needs to run a post execute then the method will return true.
+        /// </returns>
+        public bool StartingWorkItem()
+        {
+            _waitingOnQueueStopwatch.Stop();
+            _processingStopwatch.Start();
+
+            lock (this)
+            {
+                if (IsCanceled)
+                {
+                    bool result = false;
+                    if ((_workItemInfo.PostExecuteWorkItemCallback != null) &&
+                        ((_workItemInfo.CallToPostExecute & CallToPostExecute.WhenWorkItemCanceled) == CallToPostExecute.WhenWorkItemCanceled))
+                    {
+                        result = true;
+                    }
+
+                    return result;
+                }
+
+                Debug.Assert(WorkItemState.InQueue == GetWorkItemState());
+
+                // No need for a lock yet, only after the state has changed to InProgress
+                _executingThread = Thread.CurrentThread;
+
+                SetWorkItemState(WorkItemState.InProgress);
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Execute the work item and the post execute
+        /// </summary>
+        public void Execute()
+        {
+            CallToPostExecute currentCallToPostExecute = 0;
+
+            // Execute the work item if we are in the correct state
+            switch (GetWorkItemState())
+            {
+                case WorkItemState.InProgress:
+                    currentCallToPostExecute |= CallToPostExecute.WhenWorkItemNotCanceled;
+                    ExecuteWorkItem();
+                    break;
+                case WorkItemState.Canceled:
+                    currentCallToPostExecute |= CallToPostExecute.WhenWorkItemCanceled;
+                    break;
+                default:
+                    Debug.Assert(false);
+                    throw new NotSupportedException();
+            }
+
+            // Run the post execute as needed
+            if ((currentCallToPostExecute & _workItemInfo.CallToPostExecute) != 0)
+            {
+                PostExecute();
+            }
+
+            _processingStopwatch.Stop();
+        }
+
+        internal void FireWorkItemCompleted()
+        {
+            try
+            {
+                if (null != _workItemCompletedEvent)
+                {
+                    _workItemCompletedEvent(this);
+                }
+            }
+            catch // Suppress exceptions
+            { }
+        }
+
+        internal void FireWorkItemStarted()
+        {
+            try
+            {
+                if (null != _workItemStartedEvent)
+                {
+                    _workItemStartedEvent(this);
+                }
+            }
+            catch // Suppress exceptions
+            { }
+        }
+
+        /// <summary>
+        /// Execute the work item
+        /// </summary>
+        private void ExecuteWorkItem()
+        {
+
+#if !(_WINDOWS_CE) && !(_SILVERLIGHT) && !(WINDOWS_PHONE)
+            CallerThreadContext ctc = null;
+            if (null != _callerContext)
+            {
+                ctc = CallerThreadContext.Capture(_callerContext.CapturedCallContext, _callerContext.CapturedHttpContext);
+                CallerThreadContext.Apply(_callerContext);
+            }
+#endif
+
+            Exception exception = null;
+            object result = null;
+
+            try
+            {
+                try
+                {
+                    result = _callback(_state);
+                }
+                catch (Exception e)
+                {
+                    // Save the exception so we can rethrow it later
+                    exception = e;
+                }
+
+                // Remove the value of the execution thread, so it will be impossible to cancel the work item,
+                // since it is already completed.
+                // Cancelling a work item that already completed may cause the abortion of the next work item!!!
+                Thread executionThread = Interlocked.CompareExchange(ref _executingThread, null, _executingThread);
+
+                if (null == executionThread)
+                {
+                    // Oops! we are going to be aborted..., Wait here so we can catch the ThreadAbortException
+                    Thread.Sleep(60 * 1000);
+
+                    // If after 1 minute this thread was not aborted then let it continue working.
+                }
+            }
+            // We must treat the ThreadAbortException or else it will be stored in the exception variable
+            catch (ThreadAbortException tae)
+            {
+                tae.GetHashCode();
+                // Check if the work item was cancelled
+                // If we got a ThreadAbortException and the STP is not shutting down, it means the
+                // work items was cancelled.
+                if (!SmartThreadPool.CurrentThreadEntry.AssociatedSmartThreadPool.IsShuttingdown)
+                {
+#if !(_WINDOWS_CE) && !(_SILVERLIGHT) && !(WINDOWS_PHONE)
+                    Thread.ResetAbort();
+#endif
+                }
+            }
+
+#if !(_WINDOWS_CE) && !(_SILVERLIGHT) && !(WINDOWS_PHONE)
+            if (null != _callerContext)
+            {
+                CallerThreadContext.Apply(ctc);
+            }
+#endif
+
+            if (!SmartThreadPool.IsWorkItemCanceled)
+            {
+                SetResult(result, exception);
+            }
+        }
+
+        /// <summary>
+        /// Runs the post execute callback
+        /// </summary>
+        private void PostExecute()
+        {
+            if (null != _workItemInfo.PostExecuteWorkItemCallback)
+            {
+                try
+                {
+                    _workItemInfo.PostExecuteWorkItemCallback(_workItemResult);
+                }
+                catch (Exception e)
+                {
+                    Debug.Assert(null != e);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Set the result of the work item to return
+        /// </summary>
+        /// <param name="result">The result of the work item</param>
+        /// <param name="exception">The exception that was throw while the workitem executed, null
+        /// if there was no exception.</param>
+        internal void SetResult(object result, Exception exception)
+        {
+            _result = result;
+            _exception = exception;
+            SignalComplete(false);
+        }
+
+        /// <summary>
+        /// Returns the work item result
+        /// </summary>
+        /// <returns>The work item result</returns>
+        internal IWorkItemResult GetWorkItemResult()
+        {
+            return _workItemResult;
+        }
+
+        /// <summary>
+        /// Wait for all work items to complete
+        /// </summary>
+        /// <param name="waitableResults">Array of work item result objects</param>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or Timeout.Infinite (-1) to wait indefinitely.</param>
+        /// <param name="exitContext">
+        /// true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it; otherwise, false.
+        /// </param>
+        /// <param name="cancelWaitHandle">A cancel wait handle to interrupt the wait if needed</param>
+        /// <returns>
+        /// true when every work item in waitableResults has completed; otherwise false.
+        /// </returns>
+        internal static bool WaitAll(
+            IWaitableResult[] waitableResults,
+            int millisecondsTimeout,
+            bool exitContext,
+            WaitHandle cancelWaitHandle)
+        {
+            if (0 == waitableResults.Length)
+            {
+                return true;
+            }
+
+            bool success;
+            WaitHandle[] waitHandles = new WaitHandle[waitableResults.Length];
+            GetWaitHandles(waitableResults, waitHandles);
+
+            if ((null == cancelWaitHandle) && (waitHandles.Length <= 64))
+            {
+                success = STPEventWaitHandle.WaitAll(waitHandles, millisecondsTimeout, exitContext);
+            }
+            else
+            {
+                success = true;
+                int millisecondsLeft = millisecondsTimeout;
+                Stopwatch stopwatch = Stopwatch.StartNew();
+
+                WaitHandle[] whs;
+                if (null != cancelWaitHandle)
+                {
+                    whs = new WaitHandle[] { null, cancelWaitHandle };
+                }
+                else
+                {
+                    whs = new WaitHandle[] { null };
+                }
+
+                bool waitInfinitely = (Timeout.Infinite == millisecondsTimeout);
+                // Iterate over the wait handles and wait for each one to complete.
+                // We cannot use WaitHandle.WaitAll directly, because the cancelWaitHandle
+                // won't affect it.
+                // Each iteration we update the time left for the timeout.
+                for (int i = 0; i < waitableResults.Length; ++i)
+                {
+                    // WaitAny don't work with negative numbers
+                    if (!waitInfinitely && (millisecondsLeft < 0))
+                    {
+                        success = false;
+                        break;
+                    }
+
+                    whs[0] = waitHandles[i];
+                    int result = STPEventWaitHandle.WaitAny(whs, millisecondsLeft, exitContext);
+                    if ((result > 0) || (STPEventWaitHandle.WaitTimeout == result))
+                    {
+                        success = false;
+                        break;
+                    }
+
+                    if (!waitInfinitely)
+                    {
+                        // Update the time left to wait
+                        millisecondsLeft = millisecondsTimeout - (int)stopwatch.ElapsedMilliseconds;
+                    }
+                }
+            }
+            // Release the wait handles
+            ReleaseWaitHandles(waitableResults);
+
+            return success;
+        }
+
+        /// <summary>
+        /// Waits for any of the work items in the specified array to complete, cancel, or timeout
+        /// </summary>
+        /// <param name="waitableResults">Array of work item result objects</param>
+        /// <param name="millisecondsTimeout">The number of milliseconds to wait, or Timeout.Infinite (-1) to wait indefinitely.</param>
+        /// <param name="exitContext">
+        /// true to exit the synchronization domain for the context before the wait (if in a synchronized context), and reacquire it; otherwise, false.
+        /// </param>
+        /// <param name="cancelWaitHandle">A cancel wait handle to interrupt the wait if needed</param>
+        /// <returns>
+        /// The array index of the work item result that satisfied the wait, or WaitTimeout if no work item result satisfied the wait and a time interval equivalent to millisecondsTimeout has passed or the work item has been canceled.
+        /// </returns>
+        internal static int WaitAny(
+            IWaitableResult[] waitableResults,
+            int millisecondsTimeout,
+            bool exitContext,
+            WaitHandle cancelWaitHandle)
+        {
+            WaitHandle[] waitHandles;
+
+            if (null != cancelWaitHandle)
+            {
+                waitHandles = new WaitHandle[waitableResults.Length + 1];
+                GetWaitHandles(waitableResults, waitHandles);
+                waitHandles[waitableResults.Length] = cancelWaitHandle;
+            }
+            else
+            {
+                waitHandles = new WaitHandle[waitableResults.Length];
+                GetWaitHandles(waitableResults, waitHandles);
+            }
+
+            int result = STPEventWaitHandle.WaitAny(waitHandles, millisecondsTimeout, exitContext);
+
+            // Treat cancel as timeout
+            if (null != cancelWaitHandle)
+            {
+                if (result == waitableResults.Length)
+                {
+                    result = STPEventWaitHandle.WaitTimeout;
+                }
+            }
+
+            ReleaseWaitHandles(waitableResults);
+
+            return result;
+        }
+
+        /// <summary>
+        /// Fill an array of wait handles with the work items wait handles.
+        /// </summary>
+        /// <param name="waitableResults">An array of work item results</param>
+        /// <param name="waitHandles">An array of wait handles to fill</param>
+        private static void GetWaitHandles(
+            IWaitableResult[] waitableResults,
+            WaitHandle[] waitHandles)
+        {
+            for (int i = 0; i < waitableResults.Length; ++i)
+            {
+                WorkItemResult wir = waitableResults[i].GetWorkItemResult() as WorkItemResult;
+                Debug.Assert(null != wir, "All waitableResults must be WorkItemResult objects");
+
+                waitHandles[i] = wir.GetWorkItem().GetWaitHandle();
+            }
+        }
+
+        /// <summary>
+        /// Release the work items' wait handles
+        /// </summary>
+        /// <param name="waitableResults">An array of work item results</param>
+        private static void ReleaseWaitHandles(IWaitableResult[] waitableResults)
+        {
+            for (int i = 0; i < waitableResults.Length; ++i)
+            {
+                WorkItemResult wir = (WorkItemResult)waitableResults[i].GetWorkItemResult();
+
+                wir.GetWorkItem().ReleaseWaitHandle();
+            }
+        }
+
+        #endregion
+
+        #region Private Members
+
+        private WorkItemState GetWorkItemState()
+        {
+            lock (this)
+            {
+                if (WorkItemState.Completed == _workItemState)
+                {
+                    return _workItemState;
+                }
+
+                long nowTicks = DateTime.UtcNow.Ticks;
+
+                if (WorkItemState.Canceled != _workItemState && nowTicks > _expirationTime)
+                {
+                    _workItemState = WorkItemState.Canceled;
+                }
+
+                if (WorkItemState.InProgress == _workItemState)
+                {
+                    return _workItemState;
+                }
+
+                if (CanceledSmartThreadPool.IsCanceled || CanceledWorkItemsGroup.IsCanceled)
+                {
+                    return WorkItemState.Canceled;
+                }
+
+                return _workItemState;
+            }
+        }
+
+
+        /// <summary>
+        /// Sets the work item's state
+        /// </summary>
+        /// <param name="workItemState">The state to set the work item to</param>
+        private void SetWorkItemState(WorkItemState workItemState)
+        {
+            lock (this)
+            {
+                if (IsValidStatesTransition(_workItemState, workItemState))
+                {
+                    _workItemState = workItemState;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Signals that work item has been completed or canceled
+        /// </summary>
+        /// <param name="canceled">Indicates that the work item has been canceled</param>
+        private void SignalComplete(bool canceled)
+        {
+            SetWorkItemState(canceled ? WorkItemState.Canceled : WorkItemState.Completed);
+            lock (this)
+            {
+                // If someone is waiting then signal.
+                if (null != _workItemCompleted)
+                {
+                    _workItemCompleted.Set();
+                }
+            }
+        }
+
+        internal void WorkItemIsQueued()
+        {
+            _waitingOnQueueStopwatch.Start();
+        }
+
+        #endregion
+
+        #region Members exposed by WorkItemResult
+
+        /// <summary>
+        /// Cancel the work item if it didn't start running yet.
+        /// </summary>
+        /// <returns>Returns true on success or false if the work item is in progress or already completed</returns>
+        private bool Cancel(bool abortExecution)
+        {
+#if (_WINDOWS_CE)
+            if(abortExecution)
+            {
+                throw new ArgumentOutOfRangeException("abortExecution", "WindowsCE doesn't support this feature");
+            }
+#endif
+            bool success = false;
+            bool signalComplete = false;
+
+            lock (this)
+            {
+                switch (GetWorkItemState())
+                {
+                    case WorkItemState.Canceled:
+                        //Debug.WriteLine("Work item already canceled");
+                        if (abortExecution)
+                        {
+                            Thread executionThread = Interlocked.CompareExchange(ref _executingThread, null, _executingThread);
+                            if (null != executionThread)
+                            {
+                                executionThread.Abort(); // "Cancel"
+                                // No need to signalComplete, because we already cancelled this work item
+                                // so it already signaled its completion.
+                                //signalComplete = true;
+                            }
+                        }
+                        success = true;
+                        break;
+                    case WorkItemState.Completed:
+                        //Debug.WriteLine("Work item cannot be canceled");
+                        break;
+                    case WorkItemState.InProgress:
+                        if (abortExecution)
+                        {
+                            Thread executionThread = Interlocked.CompareExchange(ref _executingThread, null, _executingThread);
+                            if (null != executionThread)
+                            {
+                                executionThread.Abort(); // "Cancel"
+                                success = true;
+                                signalComplete = true;
+                            }
+                        }
+                        else
+                        {
+                            // **************************
+                            // Stock SmartThreadPool 2.2.3 sets these to true and relies on the thread to check the
+                            // WorkItem cancellation status.  However, OpenSimulator uses a different mechanism to notify
+                            // scripts of co-operative termination and the abort code also relies on this method
+                            // returning false in order to implement a small wait.
+                            //
+                            // Therefore, as was the case previously with STP, we will not signal successful cancellation
+                            // here.  It's possible that OpenSimulator code could be changed in the future to remove
+                            // the need for this change.
+                            // **************************
+                            success = false;
+                            signalComplete = false;
+                        }
+                        break;
+                    case WorkItemState.InQueue:
+                        // Signal to the wait for completion that the work
+                        // item has been completed (canceled). There is no
+                        // reason to wait for it to get out of the queue
+                        signalComplete = true;
+                        //Debug.WriteLine("Work item canceled");
+                        success = true;
+                        break;
+                }
+
+                if (signalComplete)
+                {
+                    SignalComplete(true);
+                }
+            }
+            return success;
+        }
+
+        /// <summary>
+        /// Get the result of the work item.
+        /// If the work item didn't run yet then the caller waits for the result, timeout, or cancel.
+        /// In case of error the method throws and exception
+        /// </summary>
+        /// <returns>The result of the work item</returns>
+        private object GetResult(
+            int millisecondsTimeout,
+            bool exitContext,
+            WaitHandle cancelWaitHandle)
+        {
+            Exception e;
+            object result = GetResult(millisecondsTimeout, exitContext, cancelWaitHandle, out e);
+            if (null != e)
+            {
+                throw new WorkItemResultException("The work item caused an excpetion, see the inner exception for details", e);
+            }
+            return result;
+        }
+
+        /// <summary>
+        /// Get the result of the work item.
+        /// If the work item didn't run yet then the caller waits for the result, timeout, or cancel.
+        /// In case of error the e argument is filled with the exception
+        /// </summary>
+        /// <returns>The result of the work item</returns>
+        private object GetResult(
+            int millisecondsTimeout,
+            bool exitContext,
+            WaitHandle cancelWaitHandle,
+            out Exception e)
+        {
+            e = null;
+
+            // Check for cancel
+            if (WorkItemState.Canceled == GetWorkItemState())
+            {
+                throw new WorkItemCancelException("Work item canceled");
+            }
+
+            // Check for completion
+            if (IsCompleted)
+            {
+                e = _exception;
+                return _result;
+            }
+
+            // If no cancelWaitHandle is provided
+            if (null == cancelWaitHandle)
+            {
+                WaitHandle wh = GetWaitHandle();
+
+                bool timeout = !STPEventWaitHandle.WaitOne(wh, millisecondsTimeout, exitContext);
+
+                ReleaseWaitHandle();
+
+                if (timeout)
+                {
+                    throw new WorkItemTimeoutException("Work item timeout");
+                }
+            }
+            else
+            {
+                WaitHandle wh = GetWaitHandle();
+                int result = STPEventWaitHandle.WaitAny(new WaitHandle[] { wh, cancelWaitHandle });
+                ReleaseWaitHandle();
+
+                switch (result)
+                {
+                    case 0:
+                        // The work item signaled
+                        // Note that the signal could be also as a result of canceling the
+                        // work item (not the get result)
+                        break;
+                    case 1:
+                    case STPEventWaitHandle.WaitTimeout:
+                        throw new WorkItemTimeoutException("Work item timeout");
+                    default:
+                        Debug.Assert(false);
+                        break;
+
+                }
+            }
+
+            // Check for cancel
+            if (WorkItemState.Canceled == GetWorkItemState())
+            {
+                throw new WorkItemCancelException("Work item canceled");
+            }
+
+            Debug.Assert(IsCompleted);
+
+            e = _exception;
+
+            // Return the result
+            return _result;
+        }
+
+        /// <summary>
+        /// A wait handle to wait for completion, cancel, or timeout
+        /// </summary>
+        private WaitHandle GetWaitHandle()
+        {
+            lock (this)
+            {
+                if (null == _workItemCompleted)
+                {
+                    _workItemCompleted = EventWaitHandleFactory.CreateManualResetEvent(IsCompleted);
+                }
+                ++_workItemCompletedRefCount;
+            }
+            return _workItemCompleted;
+        }
+
+        private void ReleaseWaitHandle()
+        {
+            lock (this)
+            {
+                if (null != _workItemCompleted)
+                {
+                    --_workItemCompletedRefCount;
+                    if (0 == _workItemCompletedRefCount)
+                    {
+                        _workItemCompleted.Close();
+                        _workItemCompleted = null;
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns true when the work item has completed or canceled
+        /// </summary>
+        private bool IsCompleted
+        {
+            get
+            {
+                lock (this)
+                {
+                    WorkItemState workItemState = GetWorkItemState();
+                    return ((workItemState == WorkItemState.Completed) ||
+                            (workItemState == WorkItemState.Canceled));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Returns true when the work item has canceled
+        /// </summary>
+        public bool IsCanceled
+        {
+            get
+            {
+                lock (this)
+                {
+                    return (GetWorkItemState() == WorkItemState.Canceled);
+                }
+            }
+        }
+
+        #endregion
+
+        #region IHasWorkItemPriority Members
+
+        /// <summary>
+        /// Returns the priority of the work item
+        /// </summary>
+        public WorkItemPriority WorkItemPriority
+        {
+            get
+            {
+                return _workItemInfo.WorkItemPriority;
+            }
+        }
+
+        #endregion
+
+        internal event WorkItemStateCallback OnWorkItemStarted
+        {
+            add
+            {
+                _workItemStartedEvent += value;
+            }
+            remove
+            {
+                _workItemStartedEvent -= value;
+            }
+        }
+
+        internal event WorkItemStateCallback OnWorkItemCompleted
+        {
+            add
+            {
+                _workItemCompletedEvent += value;
+            }
+            remove
+            {
+                _workItemCompletedEvent -= value;
+            }
+        }
+
+        public void DisposeOfState()
+        {
+            if (_workItemInfo.DisposeOfStateObjects)
+            {
+                IDisposable disp = _state as IDisposable;
+                if (null != disp)
+                {
+                    disp.Dispose();
+                    _state = null;
+                }
+            }
+        }
+    }
+}