decoder.go
func NewDecoderSize(reg Registry, maxSize uint64, r io.Reader) Decoder {
	var buf []byte
	return decoder{reg, maxSize, bytes.NewBuffer(buf), bufio.NewReader(r)}
}
func NewDecoderSize(reg Registry, maxSize uint64, r io.Reader) Decoder {
	var buf []byte
	return decoder{reg, maxSize, bytes.NewBuffer(buf), bufio.NewReader(r)}
}
// NewDecoderSize creates a new Decoder using a type Registry, a max size and an io.Reader.