mirror of
https://github.com/onyx-and-iris/vbantxt.git
synced 2026-03-07 02:29:17 +00:00
96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
package vbantxt
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"fmt"
|
|
|
|
"github.com/charmbracelet/log"
|
|
)
|
|
|
|
const (
|
|
vbanProtocolTxt = 0x40
|
|
vbanTxtUtf8 = 0x10
|
|
streamNameSz = 16
|
|
headerSz = 4 + 1 + 1 + 1 + 1 + 16 + 4
|
|
)
|
|
|
|
// BpsOpts defines the available baud rate options.
|
|
var BpsOpts = []int{
|
|
0, 110, 150, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 31250,
|
|
38400, 57600, 115200, 128000, 230400, 250000, 256000, 460800, 921600,
|
|
1000000, 1500000, 2000000, 3000000,
|
|
}
|
|
|
|
type packet struct {
|
|
streamname [streamNameSz]byte
|
|
bpsIndex uint8
|
|
channel uint8
|
|
framecounter uint32
|
|
hbuf *bytes.Buffer
|
|
}
|
|
|
|
// newPacket creates a new packet with the given stream name and default values for other fields.
|
|
// It validates the stream name length and ensures the default baud rate is present in BpsOpts.
|
|
func newPacket(streamname string) (packet, error) {
|
|
if len(streamname) > streamNameSz {
|
|
return packet{}, fmt.Errorf(
|
|
"streamname too long: %d chars, max %d",
|
|
len(streamname),
|
|
streamNameSz,
|
|
)
|
|
}
|
|
|
|
var streamnameBuf [streamNameSz]byte
|
|
copy(streamnameBuf[:], streamname)
|
|
|
|
bpsIndex := indexOf(BpsOpts, 256000)
|
|
if bpsIndex == -1 {
|
|
return packet{}, fmt.Errorf("default baud rate 256000 not found in BpsOpts")
|
|
}
|
|
|
|
return packet{
|
|
streamname: streamnameBuf,
|
|
bpsIndex: uint8(bpsIndex),
|
|
channel: 0,
|
|
framecounter: 0,
|
|
hbuf: bytes.NewBuffer(make([]byte, 0, headerSz)),
|
|
}, nil
|
|
}
|
|
|
|
// sr defines the samplerate for the request.
|
|
func (p *packet) sr() byte {
|
|
return byte(p.bpsIndex | vbanProtocolTxt)
|
|
}
|
|
|
|
// nbc defines the channel of the request.
|
|
func (p *packet) nbc() byte {
|
|
return byte(p.channel)
|
|
}
|
|
|
|
// header returns a fully formed packet header.
|
|
func (p *packet) header() []byte {
|
|
p.hbuf.Reset()
|
|
p.hbuf.WriteString("VBAN")
|
|
p.hbuf.WriteByte(p.sr())
|
|
p.hbuf.WriteByte(byte(0))
|
|
p.hbuf.WriteByte(p.nbc())
|
|
p.hbuf.WriteByte(byte(vbanTxtUtf8))
|
|
p.hbuf.Write(p.streamname[:])
|
|
|
|
var frameBytes [4]byte
|
|
binary.LittleEndian.PutUint32(frameBytes[:], p.framecounter)
|
|
p.hbuf.Write(frameBytes[:])
|
|
|
|
return p.hbuf.Bytes()
|
|
}
|
|
|
|
// bumpFrameCounter increments the frame counter by 1.
|
|
// The uint32 will safely wrap to 0 after reaching max value (4,294,967,295),
|
|
// which is expected behaviour for network protocol sequence numbers.
|
|
func (p *packet) bumpFrameCounter() {
|
|
p.framecounter++
|
|
|
|
log.Debugf("framecounter: %d", p.framecounter)
|
|
}
|