gpio: fix data race in ButtonDriver (hybridgroup#1027)

README.md

@@ -284,7 +284,7 @@ a shared set of drivers provided using the `gobot/drivers/gpio` package:
   - HC-SR04 Ultrasonic Ranging Module
   - HD44780 LCD controller
   - LED
-  - Makey Button
+  - Makey Button (by using driver for Button)
   - MAX7219 LED Dot Matrix
   - Motor
   - Proximity Infra Red (PIR) Motion Sensor

drivers/gpio/README.md

@@ -26,7 +26,7 @@ Gobot has a extensible system for connecting to hardware devices. The following
 - HC-SR04 Ultrasonic Ranging Module
 - HD44780 LCD controller
 - LED
-- Makey Button
+- Makey Button (by using driver for Button)
 - MAX7219 LED Dot Matrix
 - Motor
 - Proximity Infra Red (PIR) Motion Sensor

drivers/gpio/button_driver.go

@@ -8,14 +8,13 @@ import (
 
 // ButtonDriver Represents a digital Button
 type ButtonDriver struct {
-	Active       bool
-	DefaultState int
+	*Driver
+	gobot.Eventer
 	pin          string
-	name         string
+	active       bool
+	defaultState int
 	halt         chan bool
 	interval     time.Duration
-	connection   DigitalReader
-	gobot.Eventer
 }
 
 // NewButtonDriver returns a new ButtonDriver with a polling interval of
@@ -26,15 +25,16 @@ type ButtonDriver struct {
 //	time.Duration: Interval at which the ButtonDriver is polled for new information
 func NewButtonDriver(a DigitalReader, pin string, v ...time.Duration) *ButtonDriver {
 	b := &ButtonDriver{
-		name:         gobot.DefaultName("Button"),
-		connection:   a,
-		pin:          pin,
-		Active:       false,
-		DefaultState: 0,
+		Driver:       NewDriver(a.(gobot.Connection), "Button"),
 		Eventer:      gobot.NewEventer(),
+		pin:          pin,
+		active:       false,
+		defaultState: 0,
 		interval:     10 * time.Millisecond,
 		halt:         make(chan bool),
 	}
+	b.afterStart = b.initialize
+	b.beforeHalt = b.shutdown
 
 	if len(v) > 0 {
 		b.interval = v[0]
@@ -47,18 +47,39 @@ func NewButtonDriver(a DigitalReader, pin string, v ...time.Duration) *ButtonDri
 	return b
 }
 
-// Start starts the ButtonDriver and polls the state of the button at the given interval.
+// Pin returns the ButtonDrivers pin
+func (b *ButtonDriver) Pin() string { return b.pin }
+
+// Active gets the current state
+func (b *ButtonDriver) Active() bool {
+	// ensure that read and write can not interfere
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+
+	return b.active
+}
+
+// SetDefaultState for the next start.
+func (b *ButtonDriver) SetDefaultState(s int) {
+	// ensure that read and write can not interfere
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+
+	b.defaultState = s
+}
+
+// initialize the ButtonDriver and polls the state of the button at the given interval.
 //
 // Emits the Events:
 //
 //	Push int - On button push
 //	Release int - On button release
 //	Error error - On button error
-func (b *ButtonDriver) Start() (err error) {
-	state := b.DefaultState
+func (b *ButtonDriver) initialize() (err error) {
+	state := b.defaultState
 	go func() {
 		for {
-			newValue, err := b.connection.DigitalRead(b.Pin())
+			newValue, err := b.connection.(DigitalReader).DigitalRead(b.Pin())
 			if err != nil {
 				b.Publish(Error, err)
 			} else if newValue != state && newValue != -1 {
@@ -75,30 +96,21 @@ func (b *ButtonDriver) Start() (err error) {
 	return
 }
 
-// Halt stops polling the button for new information
-func (b *ButtonDriver) Halt() (err error) {
+func (b *ButtonDriver) shutdown() (err error) {
 	b.halt <- true
-	return
+	return nil
 }
 
-// Name returns the ButtonDrivers name
-func (b *ButtonDriver) Name() string { return b.name }
-
-// SetName sets the ButtonDrivers name
-func (b *ButtonDriver) SetName(n string) { b.name = n }
-
-// Pin returns the ButtonDrivers pin
-func (b *ButtonDriver) Pin() string { return b.pin }
-
-// Connection returns the ButtonDrivers Connection
-func (b *ButtonDriver) Connection() gobot.Connection { return b.connection.(gobot.Connection) }
-
 func (b *ButtonDriver) update(newValue int) {
-	if newValue != b.DefaultState {
-		b.Active = true
+	// ensure that read and write can not interfere
+	b.mutex.Lock()
+	defer b.mutex.Unlock()
+
+	if newValue != b.defaultState {
+		b.active = true
 		b.Publish(ButtonPush, newValue)
 	} else {
-		b.Active = false
+		b.active = false
 		b.Publish(ButtonRelease, newValue)
 	}
 }