/// <summary>
/// Subscribes the observer to this subject and
/// relays the live items or replays the terminal
/// event to it.
/// </summary>
/// <param name="observer">The observer to dispatch signals to.</param>
public void Subscribe(ISignalObserver <T> observer)
{
ValidationHelper.RequireNonNullRef(observer, nameof(observer));
var parent = new PublishDisposable(observer, this);
observer.OnSubscribe(parent);
if (Add(parent))
{
if (parent.IsDisposed())
{
Remove(parent);
}
}
else
{
var ex = error;
if (ex != ExceptionHelper.TERMINATED)
{
parent.OnError(ex);
}
else
{
parent.OnCompleted();
}
}
}
void Remove(PublishDisposable inner)
{
for (; ;)
{
var a = Volatile.Read(ref observers);
var n = a.Length;
if (n == 0)
{
break;
}
int j = Array.IndexOf(a, inner);
if (j < 0)
{
break;
}
var b = default(PublishDisposable[]);
if (n == 1)
{
if (refCount)
{
if (Interlocked.CompareExchange(ref observers, Terminated, a) == a)
{
DisposableHelper.Dispose(ref upstream);
break;
}
continue;
}
b = Empty;
}
else
{
b = new PublishDisposable[n - 1];
Array.Copy(a, 0, b, 0, j);
Array.Copy(a, j + 1, b, j, n - j - 1);
}
if (Interlocked.CompareExchange(ref observers, b, a) == a)
{
break;
}
}
}
bool Add(PublishDisposable inner)
{
for (; ;)
{
var a = Volatile.Read(ref observers);
if (a == Terminated)
{
return(false);
}
var n = a.Length;
var b = new PublishDisposable[n + 1];
Array.Copy(a, 0, b, 0, n);
b[n] = inner;
if (Interlocked.CompareExchange(ref observers, b, a) == a)
{
return(true);
}
}
}