module BinData::Int

def pack_directive(nbits, endian, signed)
  nwords = nbits / bits_per_word(nbits)
  directives = { 8 => "C", 16 => "S", 32 => "L", 64 => "Q" }
  d = directives[bits_per_word(nbits)]
  d += ((endian == :big) ? ">" : "<") unless d == "C"
  if signed == :signed && directives.key?(nbits)
    (d * nwords).downcase
  else
    d * nwords
  end
end