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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
#if !NO_PERF
using System.Reactive.Disposables;
using System.Threading;
namespace System.Reactive.Subjects
{
/// <summary>
/// Represents an object that is both an observable sequence as well as an observer.
/// Each notification is broadcasted to all subscribed observers.
/// </summary>
/// <typeparam name="T">The type of the elements processed by the subject.</typeparam>
public sealed class Subject<T> : ISubject<T>, IDisposable
{
private volatile IObserver<T> _observer;
/// <summary>
/// Creates a subject.
/// </summary>
public Subject()
{
_observer = NopObserver<T>.Instance;
}
/// <summary>
/// Indicates whether the subject has observers subscribed to it.
/// </summary>
public bool HasObservers
{
get
{
return _observer != NopObserver<T>.Instance && !(_observer is DoneObserver<T>) && _observer != DisposedObserver<T>.Instance;
}
}
/// <summary>
/// Notifies all subscribed observers about the end of the sequence.
/// </summary>
public void OnCompleted()
{
var oldObserver = default(IObserver<T>);
var newObserver = DoneObserver<T>.Completed;
do
{
oldObserver = _observer;
if (oldObserver == DisposedObserver<T>.Instance || oldObserver is DoneObserver<T>)
break;
#pragma warning disable 0420
} while (Interlocked.CompareExchange(ref _observer, newObserver, oldObserver) != oldObserver);
#pragma warning restore 0420
oldObserver.OnCompleted();
}
/// <summary>
/// Notifies all subscribed observers about the specified exception.
/// </summary>
/// <param name="error">The exception to send to all currently subscribed observers.</param>
/// <exception cref="ArgumentNullException"><paramref name="error"/> is null.</exception>
public void OnError(Exception error)
{
if (error == null)
throw new ArgumentNullException("error");
var oldObserver = default(IObserver<T>);
var newObserver = new DoneObserver<T> { Exception = error };
do
{
oldObserver = _observer;
if (oldObserver == DisposedObserver<T>.Instance || oldObserver is DoneObserver<T>)
break;
#pragma warning disable 0420
} while (Interlocked.CompareExchange(ref _observer, newObserver, oldObserver) != oldObserver);
#pragma warning restore 0420
oldObserver.OnError(error);
}
/// <summary>
/// Notifies all subscribed observers about the arrival of the specified element in the sequence.
/// </summary>
/// <param name="value">The value to send to all currently subscribed observers.</param>
public void OnNext(T value)
{
_observer.OnNext(value);
}
/// <summary>
/// Subscribes an observer to the subject.
/// </summary>
/// <param name="observer">Observer to subscribe to the subject.</param>
/// <returns>Disposable object that can be used to unsubscribe the observer from the subject.</returns>
/// <exception cref="ArgumentNullException"><paramref name="observer"/> is null.</exception>
public IDisposable Subscribe(IObserver<T> observer)
{
if (observer == null)
throw new ArgumentNullException("observer");
var oldObserver = default(IObserver<T>);
var newObserver = default(IObserver<T>);
do
{
oldObserver = _observer;
if (oldObserver == DisposedObserver<T>.Instance)
{
throw new ObjectDisposedException("");
}
if (oldObserver == DoneObserver<T>.Completed)
{
observer.OnCompleted();
return Disposable.Empty;
}
var done = oldObserver as DoneObserver<T>;
if (done != null)
{
observer.OnError(done.Exception);
return Disposable.Empty;
}
if (oldObserver == NopObserver<T>.Instance)
{
newObserver = observer;
}
else
{
var obs = oldObserver as Observer<T>;
if (obs != null)
{
newObserver = obs.Add(observer);
}
else
{
newObserver = new Observer<T>(new ImmutableList<IObserver<T>>(new[] { oldObserver, observer }));
}
}
#pragma warning disable 0420
} while (Interlocked.CompareExchange(ref _observer, newObserver, oldObserver) != oldObserver);
#pragma warning restore 0420
return new Subscription(this, observer);
}
class Subscription : IDisposable
{
private Subject<T> _subject;
private IObserver<T> _observer;
public Subscription(Subject<T> subject, IObserver<T> observer)
{
_subject = subject;
_observer = observer;
}
public void Dispose()
{
var observer = Interlocked.Exchange(ref _observer, null);
if (observer == null)
return;
_subject.Unsubscribe(observer);
_subject = null;
}
}
private void Unsubscribe(IObserver<T> observer)
{
var oldObserver = default(IObserver<T>);
var newObserver = default(IObserver<T>);
do
{
oldObserver = _observer;
if (oldObserver == DisposedObserver<T>.Instance || oldObserver is DoneObserver<T>)
return;
var obs = oldObserver as Observer<T>;
if (obs != null)
{
newObserver = obs.Remove(observer);
}
else
{
if (oldObserver != observer)
return;
newObserver = NopObserver<T>.Instance;
}
#pragma warning disable 0420
} while (Interlocked.CompareExchange(ref _observer, newObserver, oldObserver) != oldObserver);
#pragma warning restore 0420
}
/// <summary>
/// Releases all resources used by the current instance of the <see cref="System.Reactive.Subjects.Subject<T>"/> class and unsubscribes all observers.
/// </summary>
public void Dispose()
{
_observer = DisposedObserver<T>.Instance;
}
}
}
#else
using System.Reactive.Disposables;
using System.Threading;
namespace System.Reactive.Subjects
{
/// <summary>
/// Represents an object that is both an observable sequence as well as an observer.
/// Each notification is broadcasted to all subscribed observers.
/// </summary>
/// <typeparam name="T">The type of the elements processed by the subject.</typeparam>
public sealed class Subject<T> : ISubject<T>, IDisposable
{
bool isDisposed;
bool isStopped;
ImmutableList<IObserver<T>> observers;
object gate = new object();
Exception exception;
/// <summary>
/// Creates a subject.
/// </summary>
public Subject()
{
observers = new ImmutableList<IObserver<T>>();
}
/// <summary>
/// Notifies all subscribed observers about the end of the sequence.
/// </summary>
public void OnCompleted()
{
var os = default(IObserver<T>[]);
lock (gate)
{
CheckDisposed();
if (!isStopped)
{
os = observers.Data;
observers = new ImmutableList<IObserver<T>>();
isStopped = true;
}
}
if (os != null)
foreach (var o in os)
o.OnCompleted();
}
/// <summary>
/// Notifies all subscribed observers with the exception.
/// </summary>
/// <param name="error">The exception to send to all subscribed observers.</param>
/// <exception cref="ArgumentNullException"><paramref name="error"/> is null.</exception>
public void OnError(Exception error)
{
if (error == null)
throw new ArgumentNullException("error");
var os = default(IObserver<T>[]);
lock (gate)
{
CheckDisposed();
if (!isStopped)
{
os = observers.Data;
observers = new ImmutableList<IObserver<T>>();
isStopped = true;
exception = error;
}
}
if (os != null)
foreach (var o in os)
o.OnError(error);
}
/// <summary>
/// Notifies all subscribed observers with the value.
/// </summary>
/// <param name="value">The value to send to all subscribed observers.</param>
public void OnNext(T value)
{
var os = default(IObserver<T>[]);
lock (gate)
{
CheckDisposed();
if (!isStopped)
{
os = observers.Data;
}
}
if (os != null)
foreach (var o in os)
o.OnNext(value);
}
/// <summary>
/// Subscribes an observer to the subject.
/// </summary>
/// <param name="observer">Observer to subscribe to the subject.</param>
/// <remarks>IDisposable object that can be used to unsubscribe the observer from the subject.</remarks>
/// <exception cref="ArgumentNullException"><paramref name="observer"/> is null.</exception>
public IDisposable Subscribe(IObserver<T> observer)
{
if (observer == null)
throw new ArgumentNullException("observer");
lock (gate)
{
CheckDisposed();
if (!isStopped)
{
observers = observers.Add(observer);
return new Subscription(this, observer);
}
else if (exception != null)
{
observer.OnError(exception);
return Disposable.Empty;
}
else
{
observer.OnCompleted();
return Disposable.Empty;
}
}
}
void Unsubscribe(IObserver<T> observer)
{
lock (gate)
{
if (observers != null)
observers = observers.Remove(observer);
}
}
class Subscription : IDisposable
{
Subject<T> subject;
IObserver<T> observer;
public Subscription(Subject<T> subject, IObserver<T> observer)
{
this.subject = subject;
this.observer = observer;
}
public void Dispose()
{
var o = Interlocked.Exchange<IObserver<T>>(ref observer, null);
if (o != null)
{
subject.Unsubscribe(o);
subject = null;
}
}
}
void CheckDisposed()
{
if (isDisposed)
throw new ObjectDisposedException(string.Empty);
}
/// <summary>
/// Unsubscribe all observers and release resources.
/// </summary>
public void Dispose()
{
lock (gate)
{
isDisposed = true;
observers = null;
}
}
}
}
#endif
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