darwin: prefer sync.Map over map + Mutex

adapter_darwin.go

@@ -10,8 +10,6 @@ import (
 
 // Adapter is a connection to BLE devices.
 type Adapter struct {
-	sync.Mutex
-
 	cmd *centralManagerDelegate
 	pmd *peripheralManagerDelegate
 
@@ -21,7 +19,10 @@ type Adapter struct {
 	peripheralFoundHandler func(*Adapter, ScanResult)
 	scanChan               chan error
 	poweredChan            chan error
-	connectChan            map[string](chan cbgo.Peripheral)
+
+	// connectChan is a mapping of peripheralId -> chan cbgo.Peripheral,
+	// used to allow multiple callers to call Connect concurrently.
+	connectChan sync.Map
 
 	connectHandler func(device Addresser, connected bool)
 }
@@ -32,7 +33,7 @@ type Adapter struct {
 var DefaultAdapter = &Adapter{
 	cm:          cbgo.NewCentralManager(nil),
 	pm:          cbgo.NewPeripheralManager(nil),
-	connectChan: make(map[string]chan cbgo.Peripheral),
+	connectChan: sync.Map{},
 
 	connectHandler: func(device Addresser, connected bool) {
 		return
@@ -101,13 +102,17 @@ func (cmd *centralManagerDelegate) DidDiscoverPeripheral(cmgr cbgo.CentralManage
 
 // DidConnectPeripheral when peripheral is connected.
 func (cmd *centralManagerDelegate) DidConnectPeripheral(cmgr cbgo.CentralManager, prph cbgo.Peripheral) {
-	cmd.a.Lock()
-	defer cmd.a.Unlock()
+	id := prph.Identifier().String()
 
-	// Ignore this peripheral if we don't have a chan set up for it.
-	if ch, ok := cmd.a.connectChan[prph.Identifier().String()]; ok {
+	// Check if we have a chan allocated for this peripheral, and remove it
+	// from the map if so (it's single-use, will be garbage collected after
+	// receiver receives the peripheral).
+	//
+	// If we don't have a chan allocated, the receiving side timed out, so
+	// ignore this connection.
+	if ch, ok := cmd.a.connectChan.LoadAndDelete(id); ok {
 		// Unblock now that we're connected.
-		ch <- prph
+		ch.(chan cbgo.Peripheral) <- prph
 	}
 }
 

gap_darwin.go

@@ -106,18 +106,11 @@ func (a *Adapter) Connect(address Addresser, params ConnectionParams) (*Device,
 		return nil, fmt.Errorf("Connect failed: no peer with address: %s", adr.UUID.String())
 	}
 
-	prphCh := make(chan cbgo.Peripheral)
 	id := prphs[0].Identifier().String()
+	prphCh := make(chan cbgo.Peripheral)
 
-	a.Lock()
-	a.connectChan[id] = prphCh
-	a.Unlock()
-
-	defer func() {
-		a.Lock()
-		defer a.Unlock()
-		delete(a.connectChan, id)
-	}()
+	a.connectChan.Store(id, prphCh)
+	defer a.connectChan.Delete(id)
 
 	a.cm.Connect(prphs[0], nil)