CountdownEvent.cs

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// CountdownEvent.cs
//
// Authors:
//    Marek Safar  <marek.safar@gmail.com>
//
// Copyright (c) 2008 Jérémie "Garuma" Laval
// Copyright 2011 Xamarin Inc (http://www.xamarin.com).
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//

#if NET_4_0

namespace System.Threading
{
    [System.Diagnostics.DebuggerDisplayAttribute ("Initial Count={InitialCount}, Current Count={CurrentCount}")]
    public class CountdownEvent : IDisposable
    {
        int initialCount;
        int initial;
        ManualResetEventSlim evt;
        
        public CountdownEvent (int initialCount)
        {
            if (initialCount < 0)
                throw new ArgumentOutOfRangeException ("initialCount");

            evt = new ManualResetEventSlim (initialCount == 0);
            this.initial = this.initialCount = initialCount;
        }

        public int CurrentCount {
            get {
                return initialCount;
            }
        }
        
        public int InitialCount {
            get {
                return initial;
            }
        }
            
        public bool IsSet {
            get {
                return initialCount == 0;
            }
        }
        
        public WaitHandle WaitHandle {
            get {
                return evt.WaitHandle;
            }
        }
        
        public bool Signal ()
        {
            return Signal (1);
        }
        
        public bool Signal (int signalCount)
        {
            if (signalCount <= 0)
                throw new ArgumentOutOfRangeException ("signalCount");

            CheckDisposed ();

            int newValue;
            if (!ApplyOperation (-signalCount, out newValue))
                throw new InvalidOperationException ("The event is already set");
            
            if (newValue == 0) {
                evt.Set ();
                return true;
            }
            
            return false;
        }
        
        public void AddCount ()
        {
            AddCount (1);
        }
        
        public void AddCount (int signalCount)
        {
            if (!TryAddCount (signalCount))
                throw new InvalidOperationException ("The event is already signaled and cannot be incremented");
        }
        
        public bool TryAddCount ()
        {
            return TryAddCount (1);
        }
        
        public bool TryAddCount (int signalCount)
        {   
            if (signalCount <= 0)
                throw new ArgumentOutOfRangeException ("signalCount");

            CheckDisposed ();

            int temp;
            return ApplyOperation (signalCount, out temp);
        }
        
        bool ApplyOperation (int num, out int newValue)
        {
            int oldCount;
            
            do {
                oldCount = initialCount;
                if (oldCount == 0) {
                    newValue = 0;
                    return false;
                }
                
                newValue = oldCount + num;

                if (newValue < 0)
                    return false;
            } while (Interlocked.CompareExchange (ref initialCount, newValue, oldCount) != oldCount);
            
            return true;
        }
        
        public void Wait ()
        {
            evt.Wait ();
        }
        
        public void Wait (CancellationToken cancellationToken)
        {
            evt.Wait (cancellationToken);
        }
        
        public bool Wait (int millisecondsTimeout)
        {
            return evt.Wait (millisecondsTimeout);
        }
        
        public bool Wait(TimeSpan timeout)
        {
            return evt.Wait (timeout);
        }
        
        public bool Wait (int millisecondsTimeout, CancellationToken cancellationToken)
        {
            return evt.Wait (millisecondsTimeout, cancellationToken);
        }
        
        public bool Wait(TimeSpan timeout, CancellationToken cancellationToken)
        {
            return evt.Wait (timeout, cancellationToken);
        }

        public void Reset ()
        {
            Reset (initial);
        }
        
        public void Reset (int count)
        {
            if (count < 0)
                throw new ArgumentOutOfRangeException ("count");

            CheckDisposed ();

            initialCount = initial = count;
            if (count == 0)
                evt.Set ();
            else
                evt.Reset ();
        }
        
        public void Dispose ()
        {
            Dispose (true);
        }
        
        protected virtual void Dispose (bool disposing)
        {
            if (disposing)
                evt.Dispose ();
        }

        void CheckDisposed ()
        {
            if (evt.disposed.Value)
                throw new ObjectDisposedException ("CountdownEvent");
        }
    }
}
#endif