public SetIteratorResult MoveNext(XPathNavigator nestedNavigator) {
int order;
switch (this.state) {
case IteratorState.InitLeft:
// Fetched node from left iterator, now get initial node from right iterator
this.navLeft = nestedNavigator;
this.state = IteratorState.NeedRight;
return SetIteratorResult.InitRightIterator;
case IteratorState.NeedLeft:
this.navLeft = nestedNavigator;
break;
case IteratorState.NeedRight:
this.navRight = nestedNavigator;
break;
case IteratorState.NeedLeftAndRight:
// After fetching left node, still need right node
this.navLeft = nestedNavigator;
this.state = IteratorState.NeedRight;
return SetIteratorResult.NeedRightNode;
case IteratorState.HaveCurrent:
// Just returned left node as current, so fetch new left and right nodes
Debug.Assert(nestedNavigator == null, "null is passed to MoveNext after IteratorState.HaveCurrent has been returned.");
this.state = IteratorState.NeedLeftAndRight;
return SetIteratorResult.NeedLeftNode;
}
if (this.navLeft == null || this.navRight == null) {
// No more nodes from either left or right iterator (or both), so iteration is complete
return SetIteratorResult.NoMoreNodes;
}
// Intersect left and right sets
order = this.runtime.ComparePosition(this.navLeft, this.navRight);
if (order < 0) {
// If navLeft is positioned to a node that is before navRight, skip left node
this.state = IteratorState.NeedLeft;
return SetIteratorResult.NeedLeftNode;
}
else if (order > 0) {
// If navLeft is positioned to a node that is after navRight, so skip right node
this.state = IteratorState.NeedRight;
return SetIteratorResult.NeedRightNode;
}
// Otherwise, navLeft is positioned to the same node as navRight, so found one item in the intersection
this.state = IteratorState.HaveCurrent;
return SetIteratorResult.HaveCurrentNode;
}
