littleendian_as_big_endian_hex.nim

func tohexBE[T: uint8 or uint16 or uint32 or uint64](x: T): string =

  let bytes = cast[array[T.sizeof, byte]](x)

  result = ""
  for i in countdown(T.sizeof - 1, 0):
    result.add toHex(bytes[i])

func tohexBE(x: MpUintImpl): string =

  const size = size_mpuintimpl(x) div 8

  let bytes = cast[array[size, byte]](x)
  result = ""
  for i in countdown(size - 1, 0):
    result.add toHex(bytes[i])