// writeFrame writes frame binary representation into w.
func (ww *wsWriter) writeFrame(w io.Writer, f ws.Frame) error {
	const (
		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 {