private Stack checkInStackFrames()
{
// this is the first time we checked in
if (stackULEs == null)
{
stackULEs = new Stack();
for (savedTopOfStack = topOfStack;
savedTopOfStack != null;
savedTopOfStack = savedTopOfStack.Caller)
savedTopOfStack.DoCheckIn();
savedTopOfStack = topOfStack;
return null;
}
object zmULE = null;
if (savedTopOfStack != null)
zmULE = savedTopOfStack.DoCheckIn();
// small optimization when no changes was made in the
// current transition
if (stackULEs.Count == 0 && zmULE == null)
{
Debug.Assert(savedTopOfStack == topOfStack);
return null;
}
// the result
Stack resStack = stackULEs;
stackULEs = new Stack();
ZingMethod stackFrame = topOfStack;
// move newly pushed frames away from the result, save
// them temporarily in stackULEs; while doing that, we
// checkIn every newly pushed node
while (resStack.Count > 0 && resStack.Peek() is UndoPush)
{
//object sfULE =
// this would be the first time we check in these
// freshly pushed nodes. so we discard their undo log
// entries
stackFrame.DoCheckIn();
stackULEs.Push(resStack.Pop());
stackFrame = stackFrame.Caller;
}
// everything below should be UndoPop's or UndoResetLastFunctionCompleted,
// and if anything is to be saved, it should be right there at stackFrame
Debug.Assert(resStack.Count == 0 || resStack.Peek() is UndoPop
|| resStack.Peek() is UndoResetLastFunctionCompleted);
Debug.Assert(savedTopOfStack == stackFrame);
// insert zmULE between UndoPop objects and UndoPush
// objects
if (zmULE != null)
resStack.Push(new UndoUpdate(this, zmULE));
// move undoPush objects back into the result
while (stackULEs.Count > 0)
resStack.Push(stackULEs.Pop());
savedTopOfStack = topOfStack;
return resStack;
}
