bit0  = 0x80
		len7  = int64(125)
		len16 = int64(^(uint16(0)))
		len64 = int64(^(uint64(0)) >> 1)
	)

	bts := ww.tmp[:]
	if f.Header.Fin {
		bts[0] |= bit0
	}
	bts[0] |= f.Header.Rsv << 4
	bts[0] |= byte(f.Header.OpCode)

	var n int
	switch {
	case f.Header.Length <= len7:
		bts[1] = byte(f.Header.Length)
		n = 2

	case f.Header.Length <= len16:
		bts[1] = 126