# File lib/sup/mbox/ssh-file.rb, line 129
  def gets
    return nil if eof?
    @buf_mutex.synchronize do
      make_buf_include @offset
      expand_buf_forward while @buf.index("\n", @offset).nil? && @buf.endd < size
      returning(@buf[@offset .. (@buf.index("\n", @offset) || -1)]) { |line| @offset += line.length }
    end
  end