Method Decode

decode.go:43–80

Decode takes a single chunk of data and decodes it. Chunk expected to be validated (see Validate) before.

(chunk string)

// Decode takes a single chunk of data and decodes it.
// Chunk expected to be validated (see Validate) before.
func (d *Decoder) Decode(chunk string) error {
	idx := strings.IndexByte(chunk, '|') // expected to be validated before
	if idx == -1 {
		return fmt.Errorf("invalid frame: \"%s\"", chunk)
	}

	header := chunk[:idx]
	// continuous QR reading often sends the same chunk in a row, skip it
	if d.isCached(header) {
		return nil
	}

	var (
		blockCode       int64
		chunkLen, total int
	)
	_, err := fmt.Sscanf(header, "%d/%d/%d", &blockCode, &chunkLen, &total)
	if err != nil {
		return fmt.Errorf("invalid header: %v (%s)", err, header)
	}

	payload := chunk[idx+1:]
	lubyBlock := fountain.LTBlock{
		BlockCode: blockCode,
		Data:      []byte(payload),
	}

	if d.fd == nil {
		d.total = total
		d.chunkLen = chunkLen
		numChunks := numberOfChunks(d.total, d.chunkLen)
		d.codec = fountain.NewLubyCodec(numChunks, rand.New(fountain.NewMersenneTwister(200)), solitonDistribution(numChunks))
		d.fd = d.codec.NewDecoder(total)
	}
	d.completed = d.fd.AddBlocks([]fountain.LTBlock{lubyBlock})

	return nil
}

// Validate checks if a given chunk of data is a valid txqr protocol packet.
func (d *Decoder) Validate(chunk string) error {