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gpsd.go
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gpsd.go
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package gpsd
import (
"bufio"
"encoding/json"
"errors"
"fmt"
"io"
"net"
"time"
)
// DefaultAddress of gpsd (localhost:2947)
const DefaultAddress = "localhost:2947"
// Filter is a gpsd entry filter function
type Filter func(interface{})
// Session represents a connection to gpsd
type Session struct {
socket net.Conn
reader *bufio.Reader
filters map[string][]Filter
}
// Mode describes status of a TPV report
type Mode byte
const (
// NoValueSeen indicates no data has been received yet
NoValueSeen Mode = 0
// NoFix indicates fix has not been required yet
NoFix Mode = 1
// Mode2D represents quality of the fix
Mode2D Mode = 2
// Mode3D represents quality of the fix
Mode3D Mode = 3
)
type gpsdReport struct {
Class string `json:"class"`
}
// TPVReport is a Time-Position-Velocity report
type TPVReport struct {
Class string `json:"class"`
Tag string `json:"tag"`
Device string `json:"device"`
Mode Mode `json:"mode"`
Time time.Time `json:"time"`
Ept float64 `json:"ept"`
Lat float64 `json:"lat"`
Lon float64 `json:"lon"`
Alt float64 `json:"alt"`
Epx float64 `json:"epx"`
Epy float64 `json:"epy"`
Epv float64 `json:"epv"`
Track float64 `json:"track"`
Speed float64 `json:"speed"`
Climb float64 `json:"climb"`
Epd float64 `json:"epd"`
Eps float64 `json:"eps"`
Epc float64 `json:"epc"`
Eph float64 `json:"eph"`
}
// SKYReport reports sky view of GPS satellites
type SKYReport struct {
Class string `json:"class"`
Tag string `json:"tag"`
Device string `json:"device"`
Time time.Time `json:"time"`
Xdop float64 `json:"xdop"`
Ydop float64 `json:"ydop"`
Vdop float64 `json:"vdop"`
Tdop float64 `json:"tdop"`
Hdop float64 `json:"hdop"`
Pdop float64 `json:"pdop"`
Gdop float64 `json:"gdop"`
Satellites []Satellite `json:"satellites"`
}
// GSTReport is pseudorange noise report
type GSTReport struct {
Class string `json:"class"`
Tag string `json:"tag"`
Device string `json:"device"`
Time time.Time `json:"time"`
Rms float64 `json:"rms"`
Major float64 `json:"major"`
Minor float64 `json:"minor"`
Orient float64 `json:"orient"`
Lat float64 `json:"lat"`
Lon float64 `json:"lon"`
Alt float64 `json:"alt"`
}
// ATTReport reports vehicle-attitude from the digital compass or the gyroscope
type ATTReport struct {
Class string `json:"class"`
Tag string `json:"tag"`
Device string `json:"device"`
Time time.Time `json:"time"`
Heading float64 `json:"heading"`
MagSt string `json:"mag_st"`
Pitch float64 `json:"pitch"`
PitchSt string `json:"pitch_st"`
Yaw float64 `json:"yaw"`
YawSt string `json:"yaw_st"`
Roll float64 `json:"roll"`
RollSt string `json:"roll_st"`
Dip float64 `json:"dip"`
MagLen float64 `json:"mag_len"`
MagX float64 `json:"mag_x"`
MagY float64 `json:"mag_y"`
MagZ float64 `json:"mag_z"`
AccLen float64 `json:"acc_len"`
AccX float64 `json:"acc_x"`
AccY float64 `json:"acc_y"`
AccZ float64 `json:"acc_z"`
GyroX float64 `json:"gyro_x"`
GyroY float64 `json:"gyro_y"`
Depth float64 `json:"depth"`
Temperature float64 `json:"temperature"`
}
// VERSIONReport returns version details of gpsd client
type VERSIONReport struct {
Class string `json:"class"`
Release string `json:"release"`
Rev string `json:"rev"`
ProtoMajor int `json:"proto_major"`
ProtoMinor int `json:"proto_minor"`
Remote string `json:"remote"`
}
// DEVICESReport lists all devices connected to the system
type DEVICESReport struct {
Class string `json:"class"`
Devices []DEVICEReport `json:"devices"`
Remote string `json:"remote"`
}
// DEVICEReport reports a state of a particular device
type DEVICEReport struct {
Class string `json:"class"`
Path string `json:"path"`
Activated string `json:"activated"`
Flags int `json:"flags"`
Driver string `json:"driver"`
Subtype string `json:"subtype"`
Bps int `json:"bps"`
Parity string `json:"parity"`
Stopbits string `json:"stopbits"`
Native int `json:"native"`
Cycle float64 `json:"cycle"`
Mincycle float64 `json:"mincycle"`
}
// PPSReport is triggered on each pulse-per-second strobe from a device
type PPSReport struct {
Class string `json:"class"`
Device string `json:"device"`
RealSec float64 `json:"real_sec"`
RealMusec float64 `json:"real_musec"`
ClockSec float64 `json:"clock_sec"`
ClockMusec float64 `json:"clock_musec"`
}
// TOFFReport is triggered on each PPS strobe from a device
type TOFFReport struct {
Class string `json:"class"`
Device string `json:"device"`
RealSec float64 `json:"real_sec"`
RealNSec float64 `json:"real_nsec"`
ClockSec float64 `json:"clock_sec"`
ClockNSec float64 `json:"clock_nsec"`
}
// ERRORReport is an error response
type ERRORReport struct {
Class string `json:"class"`
Message string `json:"message"`
}
// Satellite describes a location of a GPS satellite
type Satellite struct {
PRN float64 `json:"PRN"`
Az float64 `json:"az"`
El float64 `json:"el"`
Ss float64 `json:"ss"`
Used bool `json:"used"`
GnssId float64 `json:"gnssid"`
SvId float64 `json:"svid"`
Health float64 `json:"health"`
}
// Dial opens a new connection to GPSD.
func Dial(address string) (*Session, error) {
return dialCommon(net.Dial("tcp4", address))
}
// DialTimeout opens a new connection to GPSD with a timeout.
func DialTimeout(address string, to time.Duration) (*Session, error) {
return dialCommon(net.DialTimeout("tcp4", address, to))
}
func dialCommon(c net.Conn, err error) (session *Session, e error) {
session = new(Session)
session.socket = c
if err != nil {
return nil, err
}
session.reader = bufio.NewReader(session.socket)
session.reader.ReadString('\n')
session.filters = make(map[string][]Filter)
return
}
// Watch starts watching GPSD reports in a new goroutine.
//
// Example:
//
// gps := gpsd.Dial(gpsd.DEFAULT_ADDRESS)
// done := gpsd.Watch()
// <- done
func (s *Session) Watch() (done chan bool) {
fmt.Fprintf(s.socket, "?WATCH={\"enable\":true,\"json\":true}")
done = make(chan bool)
go watch(done, s)
return
}
// SendCommand sends a command to GPSD
func (s *Session) SendCommand(command string) {
fmt.Fprintf(s.socket, "?"+command+";")
}
// AddFilter attaches a function which will be called for all
// GPSD reports with the given class. Callback functions have type Filter.
//
// Example:
//
// gps := gpsd.Init(gpsd.DEFAULT_ADDRESS)
// gps.AddFilter("TPV", func (r interface{}) {
// report := r.(*gpsd.TPVReport)
// fmt.Println(report.Time, report.Lat, report.Lon)
// })
// done := gps.Watch()
// <- done
func (s *Session) AddFilter(class string, f Filter) {
s.filters[class] = append(s.filters[class], f)
}
func (s *Session) deliverReport(class string, report interface{}) {
for _, f := range s.filters[class] {
f(report)
}
}
// Close closes the connection to GPSD
func (s *Session) Close() error {
if s.socket == nil {
return errors.New("gpsd socket is alerady closed")
}
if err := s.socket.Close(); err != nil {
return err
}
s.socket = nil
return nil
}
func watch(done chan bool, s *Session) {
// We're not using a JSON decoder because we first need to inspect
// the JSON string to determine it's "class"
for {
if line, err := s.reader.ReadString('\n'); err == nil {
var reportPeek gpsdReport
lineBytes := []byte(line)
if err = json.Unmarshal(lineBytes, &reportPeek); err == nil {
if len(s.filters[reportPeek.Class]) == 0 {
continue
}
if report, err2 := unmarshalReport(reportPeek.Class, lineBytes); err2 == nil {
s.deliverReport(reportPeek.Class, report)
} else {
fmt.Println("JSON parsing error 2:", err)
}
} else {
fmt.Println("JSON parsing error:", err)
}
} else {
if !errors.Is(err, net.ErrClosed) {
fmt.Println("Stream reader error (is gpsd running?):", err)
}
if errors.Is(err, io.EOF) || errors.Is(err, net.ErrClosed) {
break
}
}
}
done <- true
}
func unmarshalReport(class string, bytes []byte) (interface{}, error) {
var err error
switch class {
case "TPV":
var r *TPVReport
err = json.Unmarshal(bytes, &r)
return r, err
case "SKY":
var r *SKYReport
err = json.Unmarshal(bytes, &r)
return r, err
case "GST":
var r *GSTReport
err = json.Unmarshal(bytes, &r)
return r, err
case "ATT":
var r *ATTReport
err = json.Unmarshal(bytes, &r)
return r, err
case "VERSION":
var r *VERSIONReport
err = json.Unmarshal(bytes, &r)
return r, err
case "DEVICES":
var r *DEVICESReport
err = json.Unmarshal(bytes, &r)
return r, err
case "PPS":
var r *PPSReport
err = json.Unmarshal(bytes, &r)
return r, err
case "TOFF":
var r *TOFFReport
err = json.Unmarshal(bytes, &r)
return r, err
case "ERROR":
var r *ERRORReport
err = json.Unmarshal(bytes, &r)
return r, err
}
return nil, err
}