def signed_bit_fields(&block)
      ("\x80".."\xff").each do |c|
        yield c
        yield c << c # x2
        yield c << c # x4
        yield c << c # x8
      end
    end
def signed_bit_fields(&block)
      ("\x80".."\xff").each do |c|
        yield c
        yield c << c # x2
        yield c << c # x4
        yield c << c # x8
      end
    end
The range of signed bit-fields.

 @yield [bitfield]
   The given block will be passed each bit-field.

 @yieldparam [String] bitfield
   A signed bit-field (8bit - 64bit).