/// <summary>
/// Run until next yield, program termination, or completion of scheduled tasklets.
/// </summary>
public async Task Tick()
{
// Queue flip because unblocked tasks might unblock further tasks.
// TODO: Clear and flip pre-allocated lists instead of constructing a new one each time.
var oldUnblocked = unblocked;
unblocked = new List <ScheduledTaskRecord>();
oldUnblocked.AddRange(yielded);
yielded.Clear();
foreach (var continued in oldUnblocked)
{
currentTask = null;
currentTask = continued;
active.Add(currentTask);
var theContinuation = currentTask.Continuation;
await theContinuation.Continue();
currentTask = null;
}
lastScheduled = null;
oldUnblocked.Clear();
var oldActiveFrames = active;
active = new List <ScheduledTaskRecord>();
foreach (var scheduled in oldActiveFrames)
{
lastScheduled = scheduled;
// Currently, we won't bump into these exception escape clauses since we'll bomb out from the checks run after every
// active task above, but we're keeping them here for later when we try to make the scheduler more resiliant against
// rogue scripts and keep running.
//
// We need to check the call stack because we have started scheduling functions. Those return from themselves and
// fully nuke their call stacks unlike root programs.
if (lastScheduled.Frame.EscapedDotNetException != null)
{
// We want to rethrow while retaining the original stack trace.
// https://stackoverflow.com/questions/57383/how-to-rethrow-innerexception-without-losing-stack-trace-in-c
scheduled.SubmitterReceipt.NotifyEscapedException(ExceptionDispatchInfo.Capture(lastScheduled.Frame.EscapedDotNetException));
}
else if (interpreter.ExceptionEscaped(lastScheduled.Frame))
{
scheduled.SubmitterReceipt.NotifyEscapedException(ExceptionDispatchInfo.Capture(new EscapedPyException(lastScheduled.Frame.CurrentException)));
}
else if (lastScheduled.Frame.callStack.Count == 0)
{
// Executed a return statement and that nuked the whole stack. This code is done!
scheduled.SubmitterReceipt.NotifyCompleted();
}
else if (lastScheduled.Frame.BlockStack.Count == 0 &&
lastScheduled.Frame.Cursor >= lastScheduled.Frame.CodeBytes.Bytes.Length)
{
scheduled.SubmitterReceipt.NotifyCompleted();
}
else
{
active.Add(lastScheduled);
}
}
++TickCount;
}