/// <summary>
/// Subscribes the first observer to this subject and
/// starts replaying/relaying signals. All future
/// observers receive an InvalidOperationException.
/// </summary>
/// <param name="observer">The observer to subscribe with.</param>
public void Subscribe(ISignalObserver <T> observer)
{
ValidationHelper.RequireNonNullRef(observer, nameof(observer));
if (Interlocked.CompareExchange(ref once, 1, 0) == 0)
{
var inner = new MonocastDisposable(observer, this);
observer.OnSubscribe(inner);
if (Interlocked.CompareExchange(ref this.observer, inner, null) == null)
{
if (inner.IsDisposed())
{
this.observer = null;
}
else
{
Drain();
}
}
}
else
{
DisposableHelper.Error(observer, new InvalidOperationException("MonocastSubject allows at most one observer"));
}
}
void DrainFused(MonocastDisposable observer)
{
var ex = Volatile.Read(ref error);
if (!queue.IsEmpty())
{
observer.OnNext(default(T));
}
if (ex != null)
{
if (ex == ExceptionHelper.TERMINATED)
{
observer.OnCompleted();
}
else
{
observer.OnError(ex);
}
this.observer = null;
}
}
void DrainNormal(MonocastDisposable observer)
{
for (; ;)
{
if (observer.IsDisposed())
{
queue.Clear();
break;
}
else
{
var ex = Volatile.Read(ref error);
var v = queue.TryPoll(out var success);
var empty = !success;
if (ex != null && empty)
{
if (ex == ExceptionHelper.TERMINATED)
{
observer.OnCompleted();
}
else
{
observer.OnError(ex);
}
this.observer = null;
break;
}
if (empty)
{
break;
}
observer.OnNext(v);
}
}
}
void Remove(MonocastDisposable inner)
{
Interlocked.CompareExchange(ref observer, null, inner);
Terminate();
Dispose();
}
