ThreadNeutralSemaphore.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / System.Runtime.DurableInstancing / System / Runtime / ThreadNeutralSemaphore.cs / 1305376 / ThreadNeutralSemaphore.cs
                        
                        
                            //------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------

namespace System.Runtime 
{
    using System.Collections.Generic; 
    using System.Threading; 
    using System.Globalization;
    using System.Diagnostics.CodeAnalysis; 
    using System.Diagnostics;

    [Fx.Tag.SynchronizationPrimitive(Fx.Tag.BlocksUsing.PrivatePrimitive,
        SupportsAsync = true, ReleaseMethod = "Exit")] 
    class ThreadNeutralSemaphore
    { 
#if DEBUG 
        StackTrace exitStack;
#endif 

        static Action enteredAsyncCallback;

        bool aborted; 
        Func abortedExceptionGenerator;
        int count; 
        int maxCount; 

        [Fx.Tag.SynchronizationObject(Blocking = false)] 
        object ThisLock = new object();

        [Fx.Tag.SynchronizationObject]
        Queue waiters; 

        public ThreadNeutralSemaphore(int maxCount) 
            : this(maxCount, null) 
        {
        } 

        public ThreadNeutralSemaphore(int maxCount, Func abortedExceptionGenerator)
        {
            Fx.Assert(maxCount > 0, "maxCount must be positive"); 
            this.maxCount = maxCount;
            this.abortedExceptionGenerator = abortedExceptionGenerator; 
        } 

        static Action EnteredAsyncCallback 
        {
            get
            {
                if (enteredAsyncCallback == null) 
                {
                    enteredAsyncCallback = new Action(OnEnteredAsync); 
                } 

                return enteredAsyncCallback; 
            }
        }

        Queue Waiters 
        {
            get 
            { 
                if (this.waiters == null)
                { 
                    this.waiters = new Queue();
                }

                return this.waiters; 
            }
        } 
 
        public bool EnterAsync(TimeSpan timeout, FastAsyncCallback callback, object state)
        { 
            Fx.Assert(callback != null, "must have a non-null call back for async purposes");

            AsyncWaitHandle waiter = null;
 
            lock (this.ThisLock)
            { 
                if (this.aborted) 
                {
                    throw Fx.Exception.AsError(CreateObjectAbortedException()); 
                }

                if (this.count < this.maxCount)
                { 
                    this.count++;
                    return true; 
                } 

                waiter = new AsyncWaitHandle(); 
                this.Waiters.Enqueue(waiter);
            }

            return waiter.WaitAsync(EnteredAsyncCallback, new EnterAsyncData(this, waiter, callback, state), timeout); 
        }
 
        static void OnEnteredAsync(object state, TimeoutException exception) 
        {
            EnterAsyncData data = (EnterAsyncData)state; 
            ThreadNeutralSemaphore thisPtr = data.Semaphore;
            Exception exceptionToPropagate = exception;

            if (exception != null) 
            {
                if (!thisPtr.RemoveWaiter(data.Waiter)) 
                { 
                    // The timeout ----d with Exit and exit won.
                    // We've successfully entered. 
                    exceptionToPropagate = null;
                }
            }
 
            Fx.Assert(!thisPtr.waiters.Contains(data.Waiter), "The waiter should have been removed already.");
 
            if (thisPtr.aborted) 
            {
                exceptionToPropagate = thisPtr.CreateObjectAbortedException(); 
            }

            data.Callback(data.State, exceptionToPropagate);
        } 

        public bool TryEnter() 
        { 
            lock (this.ThisLock)
            { 
                if (this.count < this.maxCount)
                {
                    this.count++;
                    return true; 
                }
 
                return false; 
            }
        } 

        [Fx.Tag.Blocking(CancelMethod = "Abort")]
        public void Enter(TimeSpan timeout)
        { 
            if (!TryEnter(timeout))
            { 
                throw Fx.Exception.AsError(CreateEnterTimedOutException(timeout)); 
            }
        } 

        [Fx.Tag.Blocking(CancelMethod = "Abort")]
        public bool TryEnter(TimeSpan timeout)
        { 
            AsyncWaitHandle waiter = EnterCore();
 
            if (waiter != null) 
            {
                bool timedOut = !waiter.Wait(timeout); 

                if (this.aborted)
                {
                    throw Fx.Exception.AsError(CreateObjectAbortedException()); 
                }
 
                if (timedOut && !RemoveWaiter(waiter)) 
                {
                    // The timeout ----d with Exit and exit won. 
                    // We've successfully entered.

                    timedOut = false;
                } 

 
                return !timedOut; 
            }
 
            return true;
        }

        internal static TimeoutException CreateEnterTimedOutException(TimeSpan timeout) 
        {
            return new TimeoutException(SRCore.LockTimeoutExceptionMessage(timeout)); 
        } 

        Exception CreateObjectAbortedException() 
        {
            if (this.abortedExceptionGenerator != null)
            {
                return this.abortedExceptionGenerator(); 
            }
            else 
            { 
                return new OperationCanceledException(SRCore.ThreadNeutralSemaphoreAborted);
            } 
        }

        // remove a waiter from our queue. Returns true if successful. Used to implement timeouts.
        bool RemoveWaiter(AsyncWaitHandle waiter) 
        {
            bool removed = false; 
 
            lock (this.ThisLock)
            { 
                for (int i = this.Waiters.Count; i > 0; i--)
                {
                    AsyncWaitHandle temp = this.Waiters.Dequeue();
                    if (object.ReferenceEquals(temp, waiter)) 
                    {
                        removed = true; 
                    } 
                    else
                    { 
                        this.Waiters.Enqueue(temp);
                    }
                }
            } 

            return removed; 
        } 

        AsyncWaitHandle EnterCore() 
        {
            AsyncWaitHandle waiter;

            lock (this.ThisLock) 
            {
                if (this.aborted) 
                { 
                    throw Fx.Exception.AsError(CreateObjectAbortedException());
                } 

                if (this.count < this.maxCount)
                {
                    this.count++; 
                    return null;
                } 
 
                waiter = new AsyncWaitHandle();
                this.Waiters.Enqueue(waiter); 
            }

            return waiter;
        } 

        public int Exit() 
        { 
            AsyncWaitHandle waiter;
 
            int remainingCount = -1;
            lock (this.ThisLock)
            {
                if (this.aborted) 
                {
                    return remainingCount; 
                } 

                if (this.count == 0) 
                {
                    string message = SRCore.InvalidSemaphoreExit;

#if DEBUG 
                    if (!Fx.FastDebug && exitStack != null)
                    { 
                        string originalStack = exitStack.ToString().Replace("\r\n", "\r\n    "); 
                        message = string.Format(CultureInfo.InvariantCulture,
                            "Object synchronization method was called from an unsynchronized block of code. Previous Exit(): {0}", originalStack); 
                    }
#endif

                    throw Fx.Exception.AsError(new SynchronizationLockException(message)); 
                }
 
                if (this.waiters == null || this.waiters.Count == 0) 
                {
                    this.count--; 

#if DEBUG
                    if (!Fx.FastDebug && this.count == 0)
                    { 
                        exitStack = new StackTrace();
                    } 
#endif 

                    return this.count; 
                }

                waiter = this.waiters.Dequeue();
                remainingCount = this.count; 
            }
 
            waiter.Set(); 
            return remainingCount;
        } 

        // Abort the ThreadNeutralSemaphore object.
        public void Abort()
        { 
            lock (this.ThisLock)
            { 
                if (this.aborted) 
                {
                    return; 
                }

                this.aborted = true;
 
                if (this.waiters != null)
                { 
                    while (this.waiters.Count > 0) 
                    {
                        AsyncWaitHandle waiter = this.waiters.Dequeue(); 
                        waiter.Set();
                    }
                }
            } 
        }
 
        class EnterAsyncData 
        {
            public EnterAsyncData(ThreadNeutralSemaphore semaphore, AsyncWaitHandle waiter, FastAsyncCallback callback, object state) 
            {
                this.Waiter = waiter;
                this.Semaphore = semaphore;
                this.Callback = callback; 
                this.State = state;
            } 
 
            public ThreadNeutralSemaphore Semaphore
            { 
                get;
                set;
            }
 
            public AsyncWaitHandle Waiter
            { 
                get; 
                set;
            } 

            public FastAsyncCallback Callback
            {
                get; 
                set;
            } 
 
            public object State
            { 
                get;
                set;
            }
        } 
    }
} 

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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