private void CallbackWrapper(object state)
{
DispatcherItem item = (DispatcherItem)state;
SendOrPostCallback userCallback = item.UserCallback;
object userContext = item.UserContext;
try
{
userCallback(userContext);
}
catch (Exception excp)
{
_Dispatcher.SetLastException(excp);
_Dispatcher.Logger.Log(excp);
}
_Dispatcher.DecOutstanding();
// now dispatch any waiting items
ProcessNode(item);
}
private void ProcessNode(DispatcherItem completedItem)
{
long threadsInTree = IncThreadsInTree();
try
{
if (completedItem != null)
{
// completed item cleanup
DecThreadsInTree();
long debugN = Interlocked.Decrement(ref _ThisNodeRunning);
Debug.Assert(debugN == 0);
_Parent?.DecChildrenRunning();
completedItem = null;
}
bool looping = true;
while (looping)
{
looping = false;
// ensure that at least one pass through the dequeuing logic occurs
_Queue.Locked((queue) =>
{
// we have the queue
// we can dispatch the head of the queue if:
// a) the item is for this level, AND this tree is not running;
// or b) the item is for a lower level, AND this node is not running.
if (queue.Count > 0)
{
DispatcherItem workItem = queue.Peek();
Debug.Assert(workItem.Level >= _Level);
if ((workItem.Level == _Level) &&
(Interlocked.Add(ref _ThisNodeRunning, 0) == 0) &&
(Interlocked.Add(ref _ChildrenRunning, 0) == 0))
{
// item is for this level
// dispatch it to the threadpool
queue.Dequeue();
long debugN = Interlocked.Increment(ref _ThisNodeRunning);
Debug.Assert(debugN == 1);
IncThreadsInTree();
ThreadPool.QueueUserWorkItem(CallbackWrapper, workItem);
}
if ((workItem.Level > _Level) &&
(Interlocked.Add(ref _ThisNodeRunning, 0) == 0))
{
// item is for lower level
// enqueue it to the child
queue.Dequeue();
Interlocked.Increment(ref _ChildrenRunning);
DispatcherNode childNode = workItem.NodeList[_Level + 1];
childNode.Enqueue(workItem);
// dequeue next
looping = true;
}
}
});
} // while looping
}
finally
{
threadsInTree = DecThreadsInTree();
}
if ((threadsInTree == 0) && (_Parent != null))
{
// we are the last thread in this tree - handoff to parent
ThreadPool.QueueUserWorkItem(_Parent.AsyncProcessNode, null);
}
}
internal void Enqueue(DispatcherItem item)
{
_Queue.Locked((queue) => queue.Enqueue(item));
ThreadPool.QueueUserWorkItem(AsyncProcessNode, null);
}