public void Subscribe(ISignalObserver <T> observer)
{
var ccd = new CacheConsumerDisposable(observer, this, head);
observer.OnSubscribe(ccd);
Add(ccd);
if (ccd.IsDisposed())
{
Remove(ccd);
return;
}
if (Volatile.Read(ref once) == 0 && Interlocked.CompareExchange(ref once, 1, 0) == 0)
{
cancel?.Invoke(this);
source.Subscribe(this);
}
Drain(ccd);
}
void Drain(CacheConsumerDisposable ccd)
{
if (Interlocked.Increment(ref ccd.wip) != 1)
{
return;
}
var missed = 1;
var downstream = ccd.downstream;
for (; ;)
{
var i = ccd.index;
var n = ccd.node;
var o = ccd.offset;
if (n != null)
{
var a = n.items;
var cap = a.Length;
for (; ;)
{
if (ccd.IsDisposed())
{
n = null;
break;
}
var ex = Volatile.Read(ref terminated);
var s = Volatile.Read(ref size);
bool empty = i == s;
if (ex != null && empty)
{
if (ex == ExceptionHelper.TERMINATED)
{
downstream.OnCompleted();
}
else
{
downstream.OnError(ex);
}
n = null;
break;
}
if (empty)
{
break;
}
if (o == cap)
{
var b = n.next;
n = b;
a = b.items;
o = 0;
}
var v = a[o];
downstream.OnNext(v);
i++;
o++;
}
ccd.index = i;
ccd.node = n;
ccd.offset = o;
}
missed = Interlocked.Add(ref ccd.wip, -missed);
if (missed == 0)
{
break;
}
}
}