class BinData::IO::Write

def flushbits

To be called after all +writebits+ have been applied. 
def flushbits
  raise "Internal state error nbits = #{@wnbits}" if @wnbits >= 8
  if @wnbits > 0
    writebits(0, 8 - @wnbits, @wendian)
  end
end