Added (b *bus) HasSubscriber() for checking if a bus has any subscriber

bus.go

@@ -11,7 +11,8 @@ import (
 type Bus struct {
 	rwc ReadWriteCloser
 
-	handler []Handler
+	handler    []Handler
+	disconnect chan bool
 }
 
 // NewBusForInterfaceWithName returns a bus from the network interface with name ifaceName.
@@ -32,25 +33,30 @@ func NewBusForInterfaceWithName(ifaceName string) (*Bus, error) {
 // NewBus returns a new CAN bus.
 func NewBus(rwc ReadWriteCloser) *Bus {
 	return &Bus{
-		rwc:     rwc,
-		handler: make([]Handler, 0),
+		rwc:        rwc,
+		handler:    make([]Handler, 0),
+		disconnect: make(chan bool, 1),
 	}
 }
 
 // ConnectAndPublish starts handling CAN frames to publish them to handlers.
 func (b *Bus) ConnectAndPublish() error {
 	for {
-		err := b.publishNextFrame()
-		if err != nil {
-			return err
+		select {
+		case <-b.disconnect:
+			return nil
+		default:
+			err := b.publishNextFrame()
+			if err != nil {
+				return err
+			}
 		}
 	}
-
-	return nil
 }
 
 // Disconnect stops handling CAN frames.
 func (b *Bus) Disconnect() error {
+	b.disconnect <- true
 	return b.rwc.Close()
 }
 
@@ -75,6 +81,10 @@ func (b *Bus) Unsubscribe(handler Handler) {
 	}
 }
 
+func (b *Bus) HasSubscriber() bool {
+	return len(b.handler) > 0
+}
+
 // Publish publishes a frame on the bus.
 //
 // Frames publishes with the Publish methods are not received by handlers.

bus_test.go

@@ -75,3 +75,66 @@ func TestUnsubscribe(t *testing.T) {
 		t.Fatal(x)
 	}
 }
+
+func TestHasHandler(t *testing.T) {
+	rwc := NewEchoReadWriteCloser()
+	bus := NewBus(rwc)
+
+	if bus.HasSubscriber() != false {
+		t.Fatal("bus should not have subscriber on creation")
+	}
+
+	handler := newTestHandler()
+	bus.Subscribe(handler)
+	if bus.HasSubscriber() != true {
+		t.Fatal("bus should have subscriber after subscription")
+	}
+
+	bus.Unsubscribe(handler)
+	if bus.HasSubscriber() != false {
+		t.Fatal("bus should not have subscriber after subscriber unsubscribed")
+	}
+}
+
+func TestDisconnect(t *testing.T) {
+	rwc := NewEchoReadWriteCloser()
+	bus := NewBus(rwc)
+
+	connectAndPublishReturns := make(chan bool)
+
+	go func() {
+		bus.ConnectAndPublish()
+		connectAndPublishReturns <- true
+	}()
+	//Should make ConnectAndPublish return
+	bus.Disconnect()
+	// if it doesn't we're stuck on 1
+	timeout := time.After(100 * time.Millisecond)
+	select {
+	case <-timeout:
+		t.Fatal("bus.Disconnect does not abort ConnectAndPublish loop")
+	case <-connectAndPublishReturns:
+		//Success
+		return
+	}
+}
+
+func TestDisconnectWhenConnectAndPublishedNotCalled(t *testing.T) {
+	rwc := NewEchoReadWriteCloser()
+	bus := NewBus(rwc)
+
+	disconnected := make(chan bool)
+
+	go func() {
+		bus.Disconnect()
+		disconnected <- true
+	}()
+
+	timeout := time.After(100 * time.Millisecond)
+	select {
+	case <-timeout:
+		t.Fatal("bus.Disconnect() blocks when bus.ConnectAndPublish() not called")
+	case <-disconnected:
+		return
+	}
+}

cmd/candump.go

@@ -6,11 +6,12 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/brutella/can"
 	"log"
 	"net"
 	"os"
 	"os/signal"
+
+	"github.com/dockstavarvet/can"
 )
 
 var i = flag.String("if", "", "network interface name")

go.mod

@@ -1,3 +1,5 @@
-module github.com/brutella/can
+module github.com/dockstavarvet/can
+
+go 1.15
 
 require golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06

go.sum

@@ -1,2 +1,3 @@
+github.com/dockstavarvet/can v0.0.4/go.mod h1:jpF3R1Y7uEyvJmdl9Jo5bs2jp7+EB+AnrCrfHQmmJm4=
 golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06 h1:0oC8rFnE+74kEmuHZ46F6KHsMr5Gx2gUQPuNz28iQZM=
 golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=