Improve errors and fix nil pointer

fastboot/FastbootDevice.go

@@ -26,16 +26,20 @@ var Error = struct {
 	DeviceNotFound error
 }{
 	VarNotFound:    errors.New("variable not found"),
-	DeviceNotFound: gousb.ErrorNotFound,
+	DeviceNotFound: errors.New("device not found"),
 }
 
 type FastbootDevice struct {
-	Serial string
-	Device *gousb.Device
+	Device  *gousb.Device
+	Context *gousb.Context
+	In      *gousb.InEndpoint
+	Out     *gousb.OutEndpoint
+	Unclaim func()
 }
 
-func FindDevices(ctx *gousb.Context) ([]FastbootDevice, error) {
-	var fastbootDevices []FastbootDevice
+func FindDevices() ([]*FastbootDevice, error) {
+	ctx := gousb.NewContext()
+	var fastbootDevices []*FastbootDevice
 	devs, err := ctx.OpenDevices(func(desc *gousb.DeviceDesc) bool {
 		for _, cfg := range desc.Configs {
 			for _, ifc := range cfg.Interfaces {
@@ -44,101 +48,81 @@ func FindDevices(ctx *gousb.Context) ([]FastbootDevice, error) {
 				}
 			}
 		}
-		return false
+		return true
 	})
 
-	if err != nil {
+	if err != nil && len(devs) == 0 {
 		return nil, err
 	}
 
 	for _, dev := range devs {
-		serial, err := dev.SerialNumber()
+		intf, done, err := dev.DefaultInterface()
 		if err != nil {
 			continue
 		}
-		fastbootDevices = append(fastbootDevices, FastbootDevice{Serial: serial, Device: dev})
+		inEndpoint, err := intf.InEndpoint(0x81)
+		if err != nil {
+			continue
+		}
+		outEndpoint, err := intf.OutEndpoint(0x01)
+		if err != nil {
+			continue
+		}
+		fastbootDevices = append(fastbootDevices, &FastbootDevice{
+			Device:  dev,
+			Context: ctx,
+			In:      inEndpoint,
+			Out:     outEndpoint,
+			Unclaim: done,
+		})
 	}
 
 	return fastbootDevices, nil
 }
 
-func FindDevice(ctx *gousb.Context, serial string) (FastbootDevice, error) {
-	var fastbootDevice FastbootDevice
-	devs, err := ctx.OpenDevices(func(desc *gousb.DeviceDesc) bool {
-		for _, cfg := range desc.Configs {
-			for _, ifc := range cfg.Interfaces {
-				for _, alt := range ifc.AltSettings {
-					return alt.Protocol == 0x03 && alt.Class == 0xff && alt.SubClass == 0x42
-				}
-			}
-		}
-		return false
-	})
+func FindDevice(serial string) (*FastbootDevice, error) {
+	devs, err := FindDevices()
 
 	if err != nil {
-		return fastbootDevice, err
+		return &FastbootDevice{}, err
 	}
 
 	for _, dev := range devs {
-		serialNumber, err := dev.SerialNumber()
-		if err != nil {
+		s, e := dev.Device.SerialNumber()
+		if e != nil {
 			continue
 		}
-		if serial != serialNumber {
+		if serial != s {
 			continue
 		}
-		return FastbootDevice{Serial: serial, Device: dev}, nil
+		return dev, nil
 	}
 
-	return fastbootDevice, Error.DeviceNotFound
+	return &FastbootDevice{}, Error.DeviceNotFound
+}
+
+func (d *FastbootDevice) Close() {
+	d.Unclaim()
+	d.Device.Close()
+	d.Context.Close()
 }
 
 func (d *FastbootDevice) Send(data []byte) error {
-	intf, done, err := d.Device.DefaultInterface()
-	if err != nil {
-		return nil
-	}
-	defer done()
-
-	outEndpoint, err := intf.OutEndpoint(0x01)
-	if err != nil {
-		return nil
-	}
-
-	_, err = outEndpoint.Write(data)
+	_, err := d.Out.Write(data)
 	return err
 }
 
 func (d *FastbootDevice) GetMaxPacketSize() (int, error) {
-	intf, done, err := d.Device.DefaultInterface()
-	if err != nil {
-		return 0, err
-	}
-	defer done()
-
-	outEndpoint, err := intf.OutEndpoint(0x01)
-	if err != nil {
-		return 0, err
-	}
-
-	return outEndpoint.Desc.MaxPacketSize, nil
+	return d.Out.Desc.MaxPacketSize, nil
 }
 
 func (d *FastbootDevice) Recv() (FastbootResponseStatus, []byte, error) {
-	intf, done, err := d.Device.DefaultInterface()
-	if err != nil {
-		return Status.FAIL, nil, err
-	}
-	defer done()
-
-	inEndpoint, err := intf.InEndpoint(0x81)
-	if err != nil {
-		return Status.FAIL, nil, err
-	}
-
 	var data []byte
-	buf := make([]byte, inEndpoint.Desc.MaxPacketSize)
-	n, _ := inEndpoint.Read(buf)
+	buf := make([]byte, d.In.Desc.MaxPacketSize)
+	n, err := d.In.Read(buf)
+	if err != nil {
+		return Status.FAIL, []byte{}, err
+	}
 	data = append(data, buf[:n]...)
 	var status FastbootResponseStatus
 	switch string(data[:4]) {
@@ -154,8 +138,11 @@ func (d *FastbootDevice) Recv() (FastbootResponseStatus, []byte, error) {
 	return status, data[4:], nil
 }
 
-func (d *FastbootDevice) GerVar(variable string) (string, error) {
-	d.Send([]byte(fmt.Sprintf("getvar:%s", variable)))
+func (d *FastbootDevice) GetVar(variable string) (string, error) {
+	err := d.Send([]byte(fmt.Sprintf("getvar:%s", variable)))
+	if err != nil {
+		return "", err
+	}
 	status, resp, err := d.Recv()
 	if status == Status.FAIL {
 		err = Error.VarNotFound