func (s *Span) write(w *typed.WriteBuffer) error {
	w.WriteUint64(s.spanID)
	w.WriteUint64(s.parentID)
	w.WriteUint64(s.traceID)
	w.WriteSingleByte(s.flags)
	return w.Err()
}

func writeHeaders(w *typed.WriteBuffer, headers map[string]string) {
	w.WriteSingleByte(byte(len(headers))) // number of headers
	for k, v := range headers {
		w.WriteLen8String(k)
		w.WriteLen8String(v)
	}
}

// newWritableChunk creates a new writable chunk around a checksum and a buffer to hold data
func newWritableChunk(checksum Checksum, contents *typed.WriteBuffer) *writableChunk {
	return &writableChunk{
		size:     0,
		sizeRef:  contents.DeferUint16(),
		checksum: checksum,
		contents: contents,
	}
}

func writeHeaders(wb *typed.WriteBuffer, form http.Header) {
	numHeadersDeferred := wb.DeferUint16()
	numHeaders := uint16(0)
	for k, values := range form {
		for _, v := range values {
			wb.WriteLen16String(k)
			wb.WriteLen16String(v)
			numHeaders++
		}
	}
	numHeadersDeferred.Update(numHeaders)
}

func (f *Frame) write(msg message) error {
	var wbuf typed.WriteBuffer
	wbuf.Wrap(f.Payload[:])
	if err := msg.write(&wbuf); err != nil {
		return err
	}

	f.Header.ID = msg.ID()
	f.Header.messageType = msg.messageType()
	f.Header.SetPayloadSize(uint16(wbuf.BytesWritten()))
	return nil
}

// WriteOut writes the frame to the given io.Writer
func (f *Frame) WriteOut(w io.Writer) error {
	var wbuf typed.WriteBuffer
	wbuf.Wrap(f.headerBuffer)

	if err := f.Header.write(&wbuf); err != nil {
		return err
	}

	fullFrame := f.buffer[:f.Header.FrameSize()]
	if _, err := w.Write(fullFrame); err != nil {
		return err
	}

	return nil
}

func (m *initMessage) write(w *typed.WriteBuffer) error {
	w.WriteUint16(m.Version)
	w.WriteUint16(uint16(len(m.initParams)))

	for k, v := range m.initParams {
		w.WriteLen16String(k)
		w.WriteLen16String(v)
	}

	return w.Err()
}

func (fh *FrameHeader) write(w *typed.WriteBuffer) error {
	w.WriteUint16(fh.size)
	w.WriteSingleByte(byte(fh.messageType))
	w.WriteSingleByte(fh.reserved1)
	w.WriteUint32(fh.ID)
	w.WriteBytes(fh.reserved[:])
	return w.Err()
}

func writeVarintString(wb *typed.WriteBuffer, s string) {
	wb.WriteUvarint(uint64(len(s)))
	wb.WriteString(s)
}