Merge pull request #139 from ably-forks/feature/iterator-at

Create a redblacktree iterator at a specific node

trees/redblacktree/iterator.go

@@ -28,6 +28,11 @@ func (tree *Tree) Iterator() Iterator {
 	return Iterator{tree: tree, node: nil, position: begin}
 }
 
+// IteratorAt returns a stateful iterator whose elements are key/value pairs that is initialised at a particular node.
+func (tree *Tree) IteratorAt(node *Node) Iterator {
+	return Iterator{tree: tree, node: node, position: between}
+}
+
 // Next moves the iterator to the next element and returns true if there was a next element in the container.
 // If Next() returns true, then next element's key and value can be retrieved by Key() and Value().
 // If Next() was called for the first time, then it will point the iterator to the first element if it exists.