osc-go/pkg/osc/osc.go

package osc

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"math"
	"strings"
)

type OSCArg struct {
	Type  string
	Value any
}

type OSCMessage struct {
	Address string
	Args    []OSCArg
}

func stringToOSCBytes(rawString string) []byte {
	var sb strings.Builder

	sb.WriteString(rawString)
	sb.WriteString("\u0000")

	padLength := 4 - (len(sb.String()) % 4)
	if padLength < 4 {
		for i := 0; i < padLength; i++ {
			sb.WriteString("\u0000")
		}
	}

	return []byte(sb.String())
}

func integerToOSCBytes(number int32) []byte {
	var buf bytes.Buffer
	err := binary.Write(&buf, binary.BigEndian, number)
	if err != nil {
		panic(err)
	}
	return buf.Bytes()
}

func floatToOSCBytes(number float32) []byte {
	var buf bytes.Buffer
	err := binary.Write(&buf, binary.BigEndian, number)
	if err != nil {
		panic(err)
	}
	return buf.Bytes()
}

func byteArrayToOSCBytes(bytes []byte) []byte {
	oscBytes := []byte{}

	bytesSize := len(bytes)
	oscBytes = append(oscBytes, integerToOSCBytes(int32(bytesSize))...)
	oscBytes = append(oscBytes, bytes...)

	padLength := 4 - (bytesSize % 4)
	if padLength < 4 {
		for i := 0; i < padLength; i++ {
			oscBytes = append(oscBytes, 0)
		}
	}

	return oscBytes
}

func argsToBuffer(args []OSCArg) []byte {
	//TODO(jwetzell): add error handling
	var argBuffers = []byte{}

	for _, arg := range args {
		switch oscType := arg.Type; oscType {
		case "s":
			if value, ok := arg.Value.(string); ok {
				argBuffers = append(argBuffers, stringToOSCBytes(value)...)
			} else {
				fmt.Println("OSC arg had string type but non-string value.")
			}
		case "i":
			if value, ok := arg.Value.(int32); ok {
				argBuffers = append(argBuffers, integerToOSCBytes(value)...)
			} else {
				fmt.Println("OSC arg had integer type but non-integer value.")
			}
		case "f":
			if value, ok := arg.Value.(float32); ok {
				argBuffers = append(argBuffers, floatToOSCBytes(value)...)
			} else {
				fmt.Println("OSC arg had float type but non-float value.")
			}
		case "b":
			if value, ok := arg.Value.([]byte); ok {
				argBuffers = append(argBuffers, byteArrayToOSCBytes(value)...)
			} else {
				fmt.Println("OSC arg had blob type but non-blob value.")
			}
		default:
			fmt.Printf("unhandled osc type: %s.\n")
		}
	}
	return argBuffers
}

func ToBytes(message OSCMessage) []byte {
	oscBuffer := []byte{}

	oscBuffer = append(oscBuffer, stringToOSCBytes(message.Address)...)

	var sb strings.Builder

	sb.WriteString(",")

	for _, arg := range message.Args {
		sb.WriteString(arg.Type)
	}

	oscBuffer = append(oscBuffer, stringToOSCBytes(sb.String())...)
	oscBuffer = append(oscBuffer, argsToBuffer(message.Args)...)

	return oscBuffer
}

func readOSCString(bytes []byte) (string, []byte) {
	//TODO(jwetzell): add error handling
	oscString := ""
	stringFinished := false
	stringEndIndex := 0
	remainingBytes := []byte{}

	for index, byteIn := range bytes {
		if !stringFinished {
			if byteIn == 0 {
				oscString = string(bytes[0:index])
				stringEndIndex = index + 1
				break
			}
		}
	}

	stringPadding := 4 - (stringEndIndex % 4)

	if stringPadding < 4 {
		stringEndIndex = stringEndIndex + stringPadding
	}

	remainingBytes = bytes[stringEndIndex:]

	return oscString, remainingBytes
}

func readOSCInt(bytes []byte) (int32, []byte, error) {
	if len(bytes) < 4 {
		return 0, bytes, errors.New("int data must be at least 4 bytes large")
	}
	bits := binary.BigEndian.Uint32(bytes[0:4])
	return int32(bits), bytes[4:], nil
}

func readOSCFloat(bytes []byte) (float32, []byte, error) {
	if len(bytes) < 4 {
		return 0, bytes, errors.New("float data must be at least 4 bytes large")
	}
	bits := binary.BigEndian.Uint32(bytes[0:4])
	return math.Float32frombits(bits), bytes[4:], nil
}

func readOSCBlob(bytes []byte) ([]byte, []byte, error) {
	blobLength, remainingBytes, err := readOSCInt(bytes)

	if err != nil {
		return []byte{}, bytes, errors.New("problem reading blob data size")
	}

	if len(remainingBytes) < int(blobLength) {
		return []byte{}, bytes, errors.New("blob data specified a size larger than the remaining message data")
	}

	blobLengthPadding := 4 - (blobLength % 4)
	blobEnd := 4 + blobLength

	if blobLengthPadding < 4 {
		blobEnd = blobEnd + blobLengthPadding
	}
	return bytes[4 : 4+blobLength], bytes[blobEnd:], nil
}

func readOSCArg(bytes []byte, oscType string) (OSCArg, []byte, error) {
	var readArgError error

	oscArg := OSCArg{}
	oscArg.Type = oscType

	remainingBytes := []byte{}
	//TODO(jwetzell): add error handling
	switch oscType {
	case "s":
		argString, bytesLeft := readOSCString(bytes)
		oscArg.Value = argString
		remainingBytes = bytesLeft
	case "i":
		argInt, bytesLeft, error := readOSCInt(bytes)
		if error != nil {
			readArgError = error
		}
		oscArg.Value = argInt
		remainingBytes = bytesLeft
	case "f":
		argFloat, bytesLeft, error := readOSCFloat(bytes)
		if error != nil {
			readArgError = error
		}
		oscArg.Value = argFloat
		remainingBytes = bytesLeft
	case "b":
		argBytes, bytesLeft, error := readOSCBlob(bytes)
		if error != nil {
			readArgError = error
		}
		oscArg.Value = argBytes
		remainingBytes = bytesLeft
	default:
		fmt.Printf("unsupported osc type: %s\n", oscType)
		readArgError = errors.New("unsupported osc type: " + oscType)
	}
	return oscArg, remainingBytes, readArgError
}

func FromBytes(bytes []byte) (OSCMessage, error) {
	//TODO(jwetzell): add Message and Bundle support
	address, typeAndArgBytes := readOSCString(bytes)

	oscMessage := OSCMessage{
		Address: address,
		Args:    []OSCArg{},
	}

	typeString, argBytes := readOSCString(typeAndArgBytes)

	for index, oscType := range typeString {
		if index == 0 {
			if oscType != ',' {
				return OSCMessage{}, errors.New("type string is malformed")
			}
		} else {
			oscArg, remainingBytes, error := readOSCArg(argBytes, string(oscType))
			if error != nil {
				return oscMessage, error
			}
			argBytes = remainingBytes
			oscMessage.Args = append(oscMessage.Args, oscArg)
		}
	}

	return oscMessage, nil
}