class Concurrent::Collection::AtomicReferenceMapBackend

def clear
  return self unless current_table = table
  current_table_size = current_table.size
  deleted_count = i = 0
  while i < current_table_size
    if !(node = current_table.volatile_get(i))
      i += 1
    elsif (node_hash = node.hash) == MOVED
      current_table      = node.key
      current_table_size = current_table.size
    elsif Node.locked_hash?(node_hash)
      decrement_size(deleted_count) # opportunistically update count
      deleted_count = 0
      node.try_await_lock(current_table, i)
    else
      current_table.try_lock_via_hash(i, node, node_hash) do
        begin
          deleted_count += 1 if NULL != node.value # recheck under lock
          node.value = nil
        end while node = node.next
        current_table.volatile_set(i, nil)
        i += 1
      end
    end
  end
  decrement_size(deleted_count)
  self
end