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agwpe.go
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agwpe.go
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package agwpe
import (
"bytes"
"context"
"encoding/binary"
"errors"
"fmt"
"log"
"net"
"os"
"strconv"
"time"
)
var (
ErrTNCClosed = errors.New("TNC closed")
ErrPortClosed = errors.New("port closed")
)
type TNC struct {
conn net.Conn
demux *demux
}
func newTNC(conn net.Conn) *TNC {
t := &TNC{
conn: conn,
demux: newDemux(),
}
go t.run()
return t
}
func (t *TNC) run() {
defer debugf("TNC run() exited")
defer t.Close()
for {
var f frame
if err := t.read(&f); err != nil {
debugf("read failed: %v", err)
return
}
if !t.demux.Enqueue(f) {
return
}
}
}
func OpenTCP(addr string) (*TNC, error) {
conn, err := net.Dial("tcp", addr)
if err != nil {
return nil, err
}
return newTNC(conn), nil
}
func (t *TNC) Ping() error { _, err := t.Version(); return err }
func (t *TNC) Version() (string, error) {
resp := t.demux.NextFrame(kindVersionNumber)
t.write(versionNumberFrame())
select {
case <-time.After(3 * time.Second):
return "", fmt.Errorf("response timeout")
case f, ok := <-resp:
if !ok {
return "", ErrTNCClosed
}
if len(f.Data) != 8 {
return "", fmt.Errorf("'%c' frame with invalid data length", f.DataKind)
}
var v struct{ Major, _, Minor, _ uint16 }
binary.Read(bytes.NewReader(f.Data), binary.LittleEndian, &v)
return fmt.Sprintf("%d.%d", v.Major, v.Minor), nil
}
}
func (t *TNC) Close() error {
t.demux.Close()
return t.conn.Close()
}
func (t *TNC) RegisterPort(port int, mycall string) (*Port, error) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
p := newPort(t, uint8(port), mycall)
if err := p.register(ctx); err != nil {
t.Close()
return nil, err
}
return p, nil
}
func (t *TNC) write(f frame) error {
_, err := f.WriteTo(t.conn)
if err == nil && f.DataKind != kindOutstandingFramesForConn {
debugf("-> %v", f)
}
return err
}
func (t *TNC) read(f *frame) error {
_, err := f.ReadFrom(t.conn)
if err == nil && f.DataKind != kindOutstandingFramesForConn {
debugf("<- %v", *f)
}
return err
}
func debugf(s string, v ...interface{}) {
if t, _ := strconv.ParseBool(os.Getenv("AGWPE_DEBUG")); !t {
return
}
log.Printf(s, v...)
}