add basic start on artnet decoding

README.md

@@ -0,0 +1,2 @@
+# Art-Net
+Pure GoLang implementation of the [Art-Net protocol](https://art-net.org.uk). View the [specification here](https://art-net.org.uk/downloads/art-net.pdf).

artnet.go

@@ -0,0 +1,62 @@
+package artnet
+
+import "fmt"
+
+var (
+	OpPoll             uint16 = 0x2000
+	OpPollReply        uint16 = 0x2100
+	OpDiagData         uint16 = 0x2300
+	OpCommand          uint16 = 0x2400
+	OpDataRequest      uint16 = 0x2700
+	OpDataReply        uint16 = 0x2800
+	OpOutput           uint16 = 0x5000
+	OpDmx              uint16 = 0x5000
+	OpNzs              uint16 = 0x5100
+	OpSync             uint16 = 0x5200
+	OpAddress          uint16 = 0x6000
+	OpInput            uint16 = 0x7000
+	OpTodRequest       uint16 = 0x8000
+	OpTodData          uint16 = 0x8100
+	OpTodControl       uint16 = 0x8200
+	OpRdm              uint16 = 0x8300
+	OpRdmSub           uint16 = 0x8400
+	OpVideoSetup       uint16 = 0xa010
+	OpVideoPalette     uint16 = 0xa020
+	OpVideoData        uint16 = 0xa040
+	OpMacMaster        uint16 = 0xf000
+	OpMacSlave         uint16 = 0xf100
+	OpFirmwareMaster   uint16 = 0xf200
+	OpFirmwareReply    uint16 = 0xf300
+	OpFileTnMaster     uint16 = 0xf400
+	OpFileFnMaster     uint16 = 0xf500
+	OpFileFnReply      uint16 = 0xf600
+	OpIpProg           uint16 = 0xf800
+	OpIpProgReply      uint16 = 0xf900
+	OpMedia            uint16 = 0x9000
+	OpMediaPatch       uint16 = 0x9100
+	OpMediaControl     uint16 = 0x9200
+	OpMediaContrlReply uint16 = 0x9300
+	OpTimeCode         uint16 = 0x9700
+	OpTimeSync         uint16 = 0x9800
+	OpTrigger          uint16 = 0x9900
+	OpDirectory        uint16 = 0x9a00
+	OpDirectoryReply   uint16 = 0x9b00
+)
+
+func Decode(bytes []byte) (ArtNetPacket, error) {
+	header, err := NewHeader(bytes)
+	if err != nil {
+		return nil, err
+	}
+	switch header.OpCode {
+	case OpPoll:
+		return NewArtPoll(header, bytes)
+	case OpCommand:
+		return NewArtCommand(header, bytes)
+	case OpDmx:
+		return NewArtDmx(header, bytes)
+	default:
+		return nil, fmt.Errorf("unhandled opcode: %#x", header.OpCode)
+
+	}
+}

command.go

@@ -0,0 +1,43 @@
+package artnet
+
+import (
+	"errors"
+)
+
+type ArtCommand struct {
+	Header    *ArtNetHeader
+	EstaManHi uint8
+	EstaManLo uint8
+	Length    uint16
+	Data      string
+}
+
+func NewArtCommand(header *ArtNetHeader, data []byte) (*ArtCommand, error) {
+	artCommand := ArtCommand{
+		Header: header,
+	}
+
+	if len(data) < 18 {
+		return nil, errors.New("ArtCommand packet must be at least 14 bytes long")
+	}
+	offset := 12
+
+	artCommand.EstaManHi = data[offset]
+	artCommand.EstaManLo = data[offset+1]
+
+	artCommand.Length = uint16(data[offset+2])<<8 + uint16(data[offset+3])
+
+	commandDataOffset := offset + 4
+
+	if len(data[commandDataOffset:]) < int(artCommand.Length) {
+		return nil, errors.New("ArtCommand packet length mismatch")
+	}
+
+	artCommand.Data = string(data[commandDataOffset : commandDataOffset+int(artCommand.Length)-1])
+
+	return &artCommand, nil
+}
+
+func (ap *ArtCommand) GetOpCode() uint16 {
+	return ap.Header.OpCode
+}

dmx.go

@@ -0,0 +1,49 @@
+package artnet
+
+import (
+	"errors"
+)
+
+type ArtDmx struct {
+	Header   *ArtNetHeader
+	Sequence uint8
+	Physical uint8
+	SubUni   uint8
+	Net      uint8
+	Length   uint16
+	Data     []uint8
+}
+
+func NewArtDmx(header *ArtNetHeader, data []byte) (*ArtDmx, error) {
+	artDmx := ArtDmx{
+		Header: header,
+	}
+
+	if len(data) < 18 {
+		return nil, errors.New("ArtDmx packet must be at least 14 bytes long")
+	}
+	offset := 12
+
+	artDmx.Sequence = data[offset]
+	artDmx.Physical = data[offset+1]
+	artDmx.SubUni = data[offset+2]
+	artDmx.Net = data[offset+3]
+
+	artDmx.Length = uint16(data[offset+4])<<8 + uint16(data[offset+5])
+
+	dmxDataOffset := offset + 6
+
+	if len(data[dmxDataOffset:]) < int(artDmx.Length) {
+		return nil, errors.New("ArtDmx packet length mismatch")
+	}
+
+	artDmx.Data = make([]uint8, artDmx.Length)
+
+	copy(artDmx.Data, data[dmxDataOffset:dmxDataOffset+int(artDmx.Length)])
+
+	return &artDmx, nil
+}
+
+func (ap *ArtDmx) GetOpCode() uint16 {
+	return ap.Header.OpCode
+}

go.mod

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+module github.com/jwetzell/artnet-go
+
+go 1.23.1

packet.go

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+package artnet
+
+import (
+	"encoding/binary"
+	"errors"
+	"slices"
+)
+
+type ArtNetPacket interface {
+	GetOpCode() uint16
+}
+
+var ArtNetID []uint8 = []uint8{'A', 'r', 't', '-', 'N', 'e', 't', 0x00}
+
+type ArtNetHeader struct {
+	ID        []uint8
+	OpCode    uint16
+	ProtVerHi uint8
+	ProtVerLo uint8
+}
+
+func NewHeader(data []byte) (*ArtNetHeader, error) {
+	if len(data) < 12 {
+		return nil, errors.New("header must be at least 12 bytes")
+	}
+
+	if !slices.Equal(ArtNetID, data[0:8]) {
+		return nil, errors.New("header id does not match Art-Net ID")
+	}
+
+	return &ArtNetHeader{
+		OpCode:    binary.LittleEndian.Uint16(data[8:10]),
+		ProtVerHi: data[10],
+		ProtVerLo: data[11],
+	}, nil
+
+}

poll.go

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+package artnet
+
+import (
+	"errors"
+)
+
+type ArtPoll struct {
+	Header          *ArtNetHeader
+	Flags           uint8
+	DiagPriority    uint8
+	AddressTopHi    uint8
+	AddressTopLo    uint8
+	AddressBottomHi uint8
+	AddressBottomLo uint8
+	EstaManHi       uint8
+	EstaManLo       uint8
+	OemHi           uint8
+	OemLo           uint8
+}
+
+func NewArtPoll(header *ArtNetHeader, data []byte) (*ArtPoll, error) {
+	artPoll := ArtPoll{
+		Header: header,
+	}
+
+	if len(data) < 14 {
+		return nil, errors.New("ArtPoll packet must be at least 14 bytes long")
+	}
+	offset := 12
+	artPoll.Flags = data[offset]
+	artPoll.DiagPriority = data[offset+1]
+
+	//TODO(jwetzell): unpack extended poll fields
+
+	return &artPoll, nil
+}
+
+func (ap *ArtPoll) GetOpCode() uint16 {
+	return ap.Header.OpCode
+}