usrpserv/usrp/proto.go

package usrp

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"time"
)

func NewFrame() Frame {
	var frame Frame
	frame.Time = time.Now()
	return frame
}

func (f *Frame) Init(buff []byte, n int) error {
	if err := IsValid(buff); err != nil {
		return err
	}
	/* Can't initialize existing frame */
	if f.Metadata == METADATA {
		return errors.New("frame is already initialized")
	}
	f.Metadata = int8(buff[23])
	if f.Metadata == METADATA {
		fmt.Println("meta data")
		callLen := buff[33]
		f.Callsign = string(buff[46 : 46+callLen])
	}
	f.Seq = binary.LittleEndian.Uint32(buff[4:9])
	return nil
}

func IsValid(buff []byte) error {
	if bytes.Compare(buff[0:4], []byte{'U', 'S', 'R', 'P'}) != 0 {
		return errors.New("not a valid USRP packet")
	}
	return nil
}

func (f *Frame) Parse(buff []byte, n int) error {
	if err := IsValid(buff); err != nil {
		return err
	}
	f.Seq = binary.BigEndian.Uint32(buff[4:9])
	if len(buff[32:n]) > 320 {
		return errors.New("too many bytes")
	}
	f.PTT = int8(buff[15])
	copy(f.PCM.Data[:], buff[32:])
	return nil
}