gatts: implement write event for characteristics

adapter_sd.go

@@ -57,8 +57,9 @@ func init() {
 // Adapter is a dummy adapter: it represents the connection to the (only)
 // SoftDevice on the chip.
 type Adapter struct {
-	isDefault bool
-	handler   func(Event)
+	isDefault         bool
+	handler           func(Event)
+	charWriteHandlers []charWriteHandler
 }
 
 // DefaultAdapter is an adapter to the default Bluetooth stack on a given
@@ -123,6 +124,18 @@ func handleEvent() {
 		case C.BLE_GAP_EVT_DISCONNECTED:
 			handler(&DisconnectEvent{GAPEvent: gapEvent})
 		}
+	case id >= C.BLE_GATTS_EVT_BASE && id <= C.BLE_GATTS_EVT_LAST:
+		gattsEvent := eventBuf.evt.unionfield_gatts_evt()
+		switch id {
+		case C.BLE_GATTS_EVT_WRITE:
+			writeEvent := gattsEvent.params.unionfield_write()
+			len := writeEvent.len - writeEvent.offset
+			data := (*[255]byte)(unsafe.Pointer(&writeEvent.data[0]))[:len:len]
+			handler := DefaultAdapter.getCharWriteHandler(writeEvent.handle)
+			if handler != nil {
+				handler.callback(Connection(gattsEvent.conn_handle), int(writeEvent.offset), data)
+			}
+		}
 	}
 }
 

gatts.go

@@ -22,8 +22,9 @@ type Characteristic struct {
 type CharacteristicConfig struct {
 	Handle *Characteristic
 	UUID
-	Value []byte
-	Flags CharacteristicPermissions
+	Value      []byte
+	Flags      CharacteristicPermissions
+	WriteEvent func(client Connection, offset int, value []byte)
 }
 
 // Handle returns the numeric handle for this characteristic. This is used

gatts_sd.go

@@ -55,6 +55,36 @@ func (a *Adapter) AddService(service *Service) error {
 			char.Handle.handle = handles.value_handle
 			char.Handle.permissions = char.Flags
 		}
+		if char.Flags.Write() && char.WriteEvent != nil {
+			a.charWriteHandlers = append(a.charWriteHandlers, charWriteHandler{
+				handle:   handles.value_handle,
+				callback: char.WriteEvent,
+			})
+		}
 	}
 	return makeError(errCode)
 }
+
+// charWriteHandler contains a handler->callback mapping for characteristic
+// writes.
+type charWriteHandler struct {
+	handle   uint16
+	callback func(connection Connection, offset int, value []byte)
+}
+
+// getCharWriteHandler returns a characteristic write handler if one matches the
+// handle, or nil otherwise.
+func (a *Adapter) getCharWriteHandler(handle uint16) *charWriteHandler {
+	// Look through all handlers for a match.
+	// There is probably a way to do this more efficiently (with a hashmap for
+	// example) but the number of event handlers is likely low and improving
+	// this does not need an API change.
+	for i := range a.charWriteHandlers {
+		h := &a.charWriteHandlers[i]
+		if h.handle == handle {
+			// Handler found.
+			return h
+		}
+	}
+	return nil // not found
+}