class Sanitize

def traverse(node, &block)
  block.call(node)
  child = node.child
  while child do
    prev = child.previous_sibling
    traverse(child, &block)
    if child.parent != node
      # The child was unlinked or reparented, so traverse the previous node's
      # next sibling, or the parent's first child if there is no previous
      # node.
      child = prev ? prev.next_sibling : node.child
    else
      child = child.next_sibling
    end
  end
end