MeteorLight/listener/aps1/aps1.go

package aps1

import (
	"bytes"
	"encoding/binary"
	"encoding/json"
	"errors"
	"git.gammaspectra.live/S.O.N.G/Kirika/audio/packetizer"
	"git.gammaspectra.live/S.O.N.G/MeteorLight/listener"
	"git.gammaspectra.live/S.O.N.G/MeteorLight/queue/metadata"
	"sync/atomic"
)

type Listener struct {
	information         listener.Information
	started             atomic.Bool
	streamStartOffset   int64
	streamSamplesBuffer int64

	writer      listener.WriterFunc
	waiter      chan struct{}
	offsetStart bool
	headerBytes []byte
}

func NewListener(info listener.Information, writer listener.WriterFunc, samplesToBuffer int64, offsetStart bool, channels, sampleRate int, mimeType string) (*Listener, map[string]string) {
	headers := make(map[string]string)
	headers["x-audio-packet-stream"] = "1"
	headers["content-type"] = "application/x-audio-packet-stream"

	headerBytes := new(bytes.Buffer)

	_ = binary.Write(headerBytes, binary.LittleEndian, int64(channels))
	_ = binary.Write(headerBytes, binary.LittleEndian, int64(sampleRate))
	_ = binary.Write(headerBytes, binary.LittleEndian, int32(len(mimeType)))
	headerBytes.Write([]byte(mimeType))

	return &Listener{
		information:         info,
		writer:              writer,
		offsetStart:         offsetStart,
		streamSamplesBuffer: samplesToBuffer,
		streamStartOffset:   -1,
		headerBytes:         headerBytes.Bytes(),
		waiter:              make(chan struct{}),
	}, headers
}

func (l *Listener) Wait() {
	<-l.waiter
}

func (l *Listener) Identifier() string {
	return l.information.Identifier
}

func (l *Listener) Information() *listener.Information {
	return &l.information
}

func (l *Listener) HasStarted() bool {
	return l.started.Load()
}

func (l *Listener) Start(packets []packetizer.Packet) error {
	if l.started.Swap(true) {
		return nil
	}

	if err := l.writer((&packetStreamFrame{
		Type:              Header,
		Category:          0,
		StartSampleNumber: 0,
		DurationInSamples: 0,
		Data:              l.headerBytes,
	}).Encode()); err != nil {
		return err
	}

	if len(packets) > 0 {
		sampleBufferMin := packets[len(packets)-1].GetStartSampleNumber() - l.streamSamplesBuffer
		for _, p := range packets {
			if p.KeepMode() != packetizer.Discard || p.GetEndSampleNumber() >= sampleBufferMin {
				if err := l.Write(p); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func (l *Listener) Write(packet packetizer.Packet) error {
	if metadataPacket, ok := packet.(*metadata.Packet); ok {

		queueInfoBuf := make([]byte, binary.MaxVarintLen64)
		n := binary.PutVarint(queueInfoBuf, int64(metadataPacket.TrackEntry.Identifier))

		if err := l.writer((&packetStreamFrame{
			Type:              TrackIdentifier,
			Category:          packet.Category(),
			StartSampleNumber: packet.GetStartSampleNumber(),
			DurationInSamples: packet.GetEndSampleNumber() - packet.GetStartSampleNumber(),
			Data:              queueInfoBuf[:n],
		}).Encode()); err != nil {
			return err
		}

		if metadataBytes, err := json.Marshal(metadataPacket.TrackEntry.Metadata); err == nil {

			if err := l.writer((&packetStreamFrame{
				Type:              TrackMetadata,
				Category:          packet.Category(),
				StartSampleNumber: packet.GetStartSampleNumber(),
				DurationInSamples: packet.GetEndSampleNumber() - packet.GetStartSampleNumber(),
				Data:              metadataBytes,
			}).Encode()); err != nil {
				return err
			}
		}
		return nil
	}

	var frameType PacketStreamType
	switch packet.KeepMode() {
	case packetizer.KeepLast:
		frameType = DataKeepLast
	case packetizer.Keep:
		frameType = DataKeep
	case packetizer.GroupKeep:
		frameType = DataGroupKeep
	case packetizer.GroupDiscard:
		frameType = DataGroupDiscard
	case packetizer.Discard:
		frameType = DataDiscard
	default:
		return errors.New("unknown KeepMode")
	}

	return l.writer((&packetStreamFrame{
		Type:              frameType,
		Category:          packet.Category(),
		StartSampleNumber: packet.GetStartSampleNumber(),
		DurationInSamples: packet.GetEndSampleNumber() - packet.GetStartSampleNumber(),
		Data:              packet.GetData(),
	}).Encode())
}

func (l *Listener) Close() {
	_ = l.writer(nil)
	close(l.waiter)
}

type PacketStreamType uint64

// PacketStreamType The order of these fields is important and set on-wire protocol
const (
	Header = PacketStreamType(iota)
	DataKeepLast
	DataKeep
	DataGroupKeep
	DataGroupDiscard
	DataDiscard
	TrackIdentifier
	TrackMetadata
)

type packetStreamFrame struct {
	Type              PacketStreamType
	Category          int64
	StartSampleNumber int64
	DurationInSamples int64
	//automatically filled based on Data
	//Size              uint64
	Data []byte
}

func (p *packetStreamFrame) Encode() []byte {
	buf := new(bytes.Buffer)

	varBuf := make([]byte, binary.MaxVarintLen64)

	n := binary.PutUvarint(varBuf, uint64(p.Type))
	buf.Write(varBuf[:n])

	n = binary.PutUvarint(varBuf, uint64(p.Category))
	buf.Write(varBuf[:n])

	n = binary.PutVarint(varBuf, p.StartSampleNumber)
	buf.Write(varBuf[:n])

	n = binary.PutVarint(varBuf, p.DurationInSamples)
	buf.Write(varBuf[:n])

	n = binary.PutUvarint(varBuf, uint64(len(p.Data)))
	buf.Write(varBuf[:n])

	buf.Write(p.Data)

	return buf.Bytes()
}