SignalGate.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / cdf / src / System.Runtime.DurableInstancing / System / Runtime / SignalGate.cs / 1305376 / SignalGate.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// Copyright (c) Microsoft Corporation.  All rights reserved.
//-----------------------------------------------------------------------------

namespace System.Runtime 
{
    using System; 
    using System.Threading; 

    [Fx.Tag.SynchronizationPrimitive(Fx.Tag.BlocksUsing.NonBlocking)] 
    class SignalGate
    {
        [Fx.Tag.SynchronizationObject(Blocking=false, Kind=Fx.Tag.SynchronizationKind.InterlockedNoSpin)]
        int state; 

        public SignalGate() 
        { 
        }
 
        internal bool IsLocked
        {
            get
            { 
                return this.state == GateState.Locked;
            } 
        } 

        internal bool IsSignalled 
        {
            get
            {
                return this.state == GateState.Signalled; 
            }
        } 
 
        // Returns true if this brings the gate to the Signalled state.
        // Transitions - Locked -> SignalPending | Completed before it was unlocked 
        //               Unlocked -> Signaled
        public bool Signal()
        {
            int lastState = this.state; 
            if (lastState == GateState.Locked)
            { 
                lastState = Interlocked.CompareExchange(ref this.state, GateState.SignalPending, GateState.Locked); 
            }
            if (lastState == GateState.Unlocked) 
            {
                this.state = GateState.Signalled;
                return true;
            } 

            if (lastState != GateState.Locked) 
            { 
                ThrowInvalidSignalGateState();
            } 
            return false;
        }

        // Returns true if this brings the gate to the Signalled state. 
        // Transitions - SignalPending -> Signaled | return the AsyncResult since the callback already
        //                                         | completed and provided the result on its thread 
        //               Locked -> Unlocked 
        public bool Unlock()
        { 
            int lastState = this.state;
            if (lastState == GateState.Locked)
            {
                lastState = Interlocked.CompareExchange(ref this.state, GateState.Unlocked, GateState.Locked); 
            }
            if (lastState == GateState.SignalPending) 
            { 
                this.state = GateState.Signalled;
                return true; 
            }

            if (lastState != GateState.Locked)
            { 
                ThrowInvalidSignalGateState();
            } 
            return false; 
        }
 
        // This is factored out to allow Signal and Unlock to be inlined.
        void ThrowInvalidSignalGateState()
        {
            throw Fx.Exception.AsError(new InvalidOperationException(SRCore.InvalidSemaphoreExit)); 
        }
 
        static class GateState 
        {
            public const int Locked = 0; 
            public const int SignalPending = 1;
            public const int Unlocked = 2;
            public const int Signalled = 3;
        } 
    }
 
    [Fx.Tag.SynchronizationPrimitive(Fx.Tag.BlocksUsing.NonBlocking)] 
    class SignalGate : SignalGate
    { 
        T result;

        public SignalGate()
            : base() 
        {
        } 
 
        public bool Signal(T result)
        { 
            this.result = result;
            return Signal();
        }
 
        public bool Unlock(out T result)
        { 
            if (Unlock()) 
            {
                result = this.result; 
                return true;
            }

            result = default(T); 
            return false;
        } 
    } 
}

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

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