5746ccfb60
This is unnecessary because the values are passed by value in other cases, and can in some cases lead to more (heap or stack) allocation than is necessary.
308 lines
9 KiB
Go
308 lines
9 KiB
Go
//go:build !baremetal
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package bluetooth
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import (
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"errors"
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"sort"
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"strings"
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"time"
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"github.com/godbus/dbus/v5"
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)
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var (
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errDupNotif = errors.New("unclosed notifications")
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)
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// UUIDWrapper is a type alias for UUID so we ensure no conflicts with
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// struct method of the same name.
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type uuidWrapper = UUID
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// DeviceService is a BLE service on a connected peripheral device.
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type DeviceService struct {
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uuidWrapper
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adapter *Adapter
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servicePath string
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}
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// UUID returns the UUID for this DeviceService.
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func (s DeviceService) UUID() UUID {
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return s.uuidWrapper
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}
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// DiscoverServices starts a service discovery procedure. Pass a list of service
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// UUIDs you are interested in to this function. Either a slice of all services
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// is returned (of the same length as the requested UUIDs and in the same
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// order), or if some services could not be discovered an error is returned.
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//
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// Passing a nil slice of UUIDs will return a complete list of
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// services.
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//
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// On Linux with BlueZ, this just waits for the ServicesResolved signal (if
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// services haven't been resolved yet) and uses this list of cached services.
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func (d Device) DiscoverServices(uuids []UUID) ([]DeviceService, error) {
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start := time.Now()
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for {
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resolved, err := d.device.GetProperty("org.bluez.Device1.ServicesResolved")
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if err != nil {
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return nil, err
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}
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if resolved.Value().(bool) {
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break
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}
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// This is a terrible hack, but I couldn't find another way.
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// TODO: actually there is, by waiting for a property change event of
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// ServicesResolved.
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time.Sleep(10 * time.Millisecond)
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if time.Since(start) > 10*time.Second {
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return nil, errors.New("timeout on DiscoverServices")
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}
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}
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services := []DeviceService{}
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uuidServices := make(map[UUID]struct{})
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servicesFound := 0
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// Iterate through all objects managed by BlueZ, hoping to find the services
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// we're looking for.
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var list map[dbus.ObjectPath]map[string]map[string]dbus.Variant
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err := d.adapter.bluez.Call("org.freedesktop.DBus.ObjectManager.GetManagedObjects", 0).Store(&list)
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if err != nil {
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return nil, err
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}
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objects := make([]string, 0, len(list))
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for objectPath := range list {
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objects = append(objects, string(objectPath))
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}
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sort.Strings(objects)
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for _, objectPath := range objects {
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if !strings.HasPrefix(objectPath, string(d.device.Path())+"/service") {
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continue
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}
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properties, ok := list[dbus.ObjectPath(objectPath)]["org.bluez.GattService1"]
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if !ok {
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continue
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}
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serviceUUID, _ := ParseUUID(properties["UUID"].Value().(string))
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if len(uuids) > 0 {
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found := false
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for _, uuid := range uuids {
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if uuid == serviceUUID {
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// One of the services we're looking for.
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found = true
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break
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}
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}
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if !found {
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continue
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}
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}
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if _, ok := uuidServices[serviceUUID]; ok {
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// There is more than one service with the same UUID?
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// Don't overwrite it, to keep the servicesFound count correct.
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continue
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}
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ds := DeviceService{
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uuidWrapper: serviceUUID,
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adapter: d.adapter,
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servicePath: objectPath,
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}
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services = append(services, ds)
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servicesFound++
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uuidServices[serviceUUID] = struct{}{}
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}
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if servicesFound < len(uuids) {
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return nil, errors.New("bluetooth: could not find some services")
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}
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return services, nil
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}
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// DeviceCharacteristic is a BLE characteristic on a connected peripheral
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// device.
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type DeviceCharacteristic struct {
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uuidWrapper
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adapter *Adapter
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characteristic dbus.BusObject
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property chan *dbus.Signal // channel where notifications are reported
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propertiesChangedMatchOption dbus.MatchOption // the same value must be passed to RemoveMatchSignal
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}
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// UUID returns the UUID for this DeviceCharacteristic.
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func (c DeviceCharacteristic) UUID() UUID {
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return c.uuidWrapper
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}
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// DiscoverCharacteristics discovers characteristics in this service. Pass a
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// list of characteristic UUIDs you are interested in to this function. Either a
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// list of all requested services is returned, or if some services could not be
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// discovered an error is returned. If there is no error, the characteristics
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// slice has the same length as the UUID slice with characteristics in the same
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// order in the slice as in the requested UUID list.
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//
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// Passing a nil slice of UUIDs will return a complete
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// list of characteristics.
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func (s DeviceService) DiscoverCharacteristics(uuids []UUID) ([]DeviceCharacteristic, error) {
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var chars []DeviceCharacteristic
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if len(uuids) > 0 {
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// The caller wants to get a list of characteristics in a specific
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// order.
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chars = make([]DeviceCharacteristic, len(uuids))
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}
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// Iterate through all objects managed by BlueZ, hoping to find the
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// characteristic we're looking for.
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var list map[dbus.ObjectPath]map[string]map[string]dbus.Variant
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err := s.adapter.bluez.Call("org.freedesktop.DBus.ObjectManager.GetManagedObjects", 0).Store(&list)
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if err != nil {
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return nil, err
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}
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objects := make([]string, 0, len(list))
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for objectPath := range list {
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objects = append(objects, string(objectPath))
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}
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sort.Strings(objects)
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for _, objectPath := range objects {
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if !strings.HasPrefix(objectPath, s.servicePath+"/char") {
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continue
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}
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properties, ok := list[dbus.ObjectPath(objectPath)]["org.bluez.GattCharacteristic1"]
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if !ok {
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continue
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}
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cuuid, _ := ParseUUID(properties["UUID"].Value().(string))
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char := DeviceCharacteristic{
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uuidWrapper: cuuid,
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adapter: s.adapter,
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characteristic: s.adapter.bus.Object("org.bluez", dbus.ObjectPath(objectPath)),
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}
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if len(uuids) > 0 {
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// The caller wants to get a list of characteristics in a specific
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// order. Check whether this is one of those.
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for i, uuid := range uuids {
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if chars[i] != (DeviceCharacteristic{}) {
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// To support multiple identical characteristics, we need to
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// ignore the characteristics that are already found. See:
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// https://github.com/tinygo-org/bluetooth/issues/131
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continue
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}
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if cuuid == uuid {
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// one of the characteristics we're looking for.
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chars[i] = char
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break
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}
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}
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} else {
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// The caller wants to get all characteristics, in any order.
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chars = append(chars, char)
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}
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}
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// Check that we have found all characteristics.
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for _, char := range chars {
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if char == (DeviceCharacteristic{}) {
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return nil, errors.New("bluetooth: could not find some characteristics")
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}
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}
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return chars, nil
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}
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// WriteWithoutResponse replaces the characteristic value with a new value. The
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// call will return before all data has been written. A limited number of such
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// writes can be in flight at any given time. This call is also known as a
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// "write command" (as opposed to a write request).
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func (c DeviceCharacteristic) WriteWithoutResponse(p []byte) (n int, err error) {
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err = c.characteristic.Call("org.bluez.GattCharacteristic1.WriteValue", 0, p, map[string]dbus.Variant(nil)).Err
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if err != nil {
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return 0, err
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}
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return len(p), nil
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}
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// EnableNotifications enables notifications in the Client Characteristic
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// Configuration Descriptor (CCCD). This means that most peripherals will send a
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// notification with a new value every time the value of the characteristic
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// changes.
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//
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// Users may call EnableNotifications with a nil callback to disable notifications.
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func (c DeviceCharacteristic) EnableNotifications(callback func(buf []byte)) error {
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switch callback {
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default:
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if c.property != nil {
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return errDupNotif
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}
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// Start watching for changes in the Value property.
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c.property = make(chan *dbus.Signal)
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c.adapter.bus.Signal(c.property)
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c.propertiesChangedMatchOption = dbus.WithMatchInterface("org.freedesktop.DBus.Properties")
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c.adapter.bus.AddMatchSignal(c.propertiesChangedMatchOption)
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err := c.characteristic.Call("org.bluez.GattCharacteristic1.StartNotify", 0).Err
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if err != nil {
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return err
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}
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go func() {
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for sig := range c.property {
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if sig.Name == "org.freedesktop.DBus.Properties.PropertiesChanged" {
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interfaceName := sig.Body[0].(string)
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if interfaceName != "org.bluez.GattCharacteristic1" {
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continue
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}
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if sig.Path != c.characteristic.Path() {
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continue
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}
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changes := sig.Body[1].(map[string]dbus.Variant)
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if value, ok := changes["Value"].Value().([]byte); ok {
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callback(value)
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}
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}
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}
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}()
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return nil
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case nil:
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if c.property == nil {
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return nil
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}
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err := c.adapter.bus.RemoveMatchSignal(c.propertiesChangedMatchOption)
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c.adapter.bus.RemoveSignal(c.property)
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c.property = nil
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return err
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}
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}
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// GetMTU returns the MTU for the characteristic.
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func (c DeviceCharacteristic) GetMTU() (uint16, error) {
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mtu, err := c.characteristic.GetProperty("org.bluez.GattCharacteristic1.MTU")
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if err != nil {
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return uint16(0), err
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}
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return mtu.Value().(uint16), nil
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}
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// Read reads the current characteristic value.
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func (c DeviceCharacteristic) Read(data []byte) (int, error) {
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options := make(map[string]interface{})
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var result []byte
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err := c.characteristic.Call("org.bluez.GattCharacteristic1.ReadValue", 0, options).Store(&result)
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if err != nil {
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return 0, err
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}
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copy(data, result)
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return len(result), nil
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}
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