0087e0549b
This is a breaking change, but I believe it is necessary for correctness. Because maps have an undefined iteration order, the actual advertised packet could change each time which I think is a bad thing. In addition to that, using a slice should be much more lightweight than using a map. I've also added some tests (that should have been there in the first place) and added some manufacturer data to the advertisement example. Furthermore, I've optimized the code that constructs manufacturer data for raw advertisement payloads, it should now be entirely free of heap allocations.
391 lines
13 KiB
Go
391 lines
13 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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"fmt"
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"strings"
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"sync/atomic"
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"github.com/godbus/dbus/v5"
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"github.com/godbus/dbus/v5/prop"
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)
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var errAdvertisementNotStarted = errors.New("bluetooth: stop advertisement that was not started")
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var errAdvertisementAlreadyStarted = errors.New("bluetooth: start advertisement that was already started")
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// Unique ID per advertisement (to generate a unique object path).
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var advertisementID uint64
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// Address contains a Bluetooth MAC address.
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type Address struct {
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MACAddress
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}
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// Advertisement encapsulates a single advertisement instance.
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type Advertisement struct {
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adapter *Adapter
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properties *prop.Properties
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path dbus.ObjectPath
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}
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// DefaultAdvertisement returns the default advertisement instance but does not
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// configure it.
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func (a *Adapter) DefaultAdvertisement() *Advertisement {
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if a.defaultAdvertisement == nil {
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a.defaultAdvertisement = &Advertisement{
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adapter: a,
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}
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}
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return a.defaultAdvertisement
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}
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// Configure this advertisement.
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//
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// On Linux with BlueZ, it is not possible to set the advertisement interval.
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func (a *Advertisement) Configure(options AdvertisementOptions) error {
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if a.properties != nil {
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panic("todo: configure advertisement a second time")
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}
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var serviceUUIDs []string
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for _, uuid := range options.ServiceUUIDs {
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serviceUUIDs = append(serviceUUIDs, uuid.String())
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}
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// Convert map[uint16][]byte to map[uint16]any because that's what BlueZ needs.
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manufacturerData := map[uint16]any{}
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for _, element := range options.ManufacturerData {
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manufacturerData[element.CompanyID] = element.Data
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}
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// Build an org.bluez.LEAdvertisement1 object, to be exported over DBus.
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// See:
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// https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/org.bluez.LEAdvertisement.rst
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id := atomic.AddUint64(&advertisementID, 1)
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a.path = dbus.ObjectPath(fmt.Sprintf("/org/tinygo/bluetooth/advertisement%d", id))
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propsSpec := map[string]map[string]*prop.Prop{
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"org.bluez.LEAdvertisement1": {
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"Type": {Value: "broadcast"},
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"ServiceUUIDs": {Value: serviceUUIDs},
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"ManufacturerData": {Value: manufacturerData},
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"LocalName": {Value: options.LocalName},
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// The documentation states:
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// > Timeout of the advertisement in seconds. This defines the
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// > lifetime of the advertisement.
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// however, the value 0 also works, and presumably means "no
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// timeout".
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"Timeout": {Value: uint16(0)},
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// TODO: MinInterval and MaxInterval (experimental as of BlueZ 5.71)
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},
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}
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props, err := prop.Export(a.adapter.bus, a.path, propsSpec)
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if err != nil {
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return err
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}
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a.properties = props
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return nil
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}
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// Start advertisement. May only be called after it has been configured.
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func (a *Advertisement) Start() error {
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// Register our advertisement object to start advertising.
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err := a.adapter.adapter.Call("org.bluez.LEAdvertisingManager1.RegisterAdvertisement", 0, a.path, map[string]interface{}{}).Err
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if err != nil {
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if err, ok := err.(dbus.Error); ok && err.Name == "org.bluez.Error.AlreadyExists" {
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return errAdvertisementAlreadyStarted
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}
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return fmt.Errorf("bluetooth: could not start advertisement: %w", err)
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}
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// Make us discoverable.
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err = a.adapter.adapter.SetProperty("org.bluez.Adapter1.Discoverable", dbus.MakeVariant(true))
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if err != nil {
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return fmt.Errorf("bluetooth: could not start advertisement: %w", err)
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}
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return nil
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}
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// Stop advertisement. May only be called after it has been started.
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func (a *Advertisement) Stop() error {
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err := a.adapter.adapter.Call("org.bluez.LEAdvertisingManager1.UnregisterAdvertisement", 0, a.path).Err
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if err != nil {
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if err, ok := err.(dbus.Error); ok && err.Name == "org.bluez.Error.DoesNotExist" {
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return errAdvertisementNotStarted
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}
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return fmt.Errorf("bluetooth: could not stop advertisement: %w", err)
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}
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return nil
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}
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// Scan starts a BLE scan. It is stopped by a call to StopScan. A common pattern
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// is to cancel the scan when a particular device has been found.
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//
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// On Linux with BlueZ, incoming packets cannot be observed directly. Instead,
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// existing devices are watched for property changes. This closely simulates the
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// behavior as if the actual packets were observed, but it has flaws: it is
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// possible some events are missed and perhaps even possible that some events
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// are duplicated.
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func (a *Adapter) Scan(callback func(*Adapter, ScanResult)) error {
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if a.scanCancelChan != nil {
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return errScanning
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}
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// Channel that will be closed when the scan is stopped.
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// Detecting whether the scan is stopped can be done by doing a non-blocking
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// read from it. If it succeeds, the scan is stopped.
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cancelChan := make(chan struct{})
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a.scanCancelChan = cancelChan
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// This appears to be necessary to receive any BLE discovery results at all.
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defer a.adapter.Call("org.bluez.Adapter1.SetDiscoveryFilter", 0)
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err := a.adapter.Call("org.bluez.Adapter1.SetDiscoveryFilter", 0, map[string]interface{}{
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"Transport": "le",
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}).Err
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if err != nil {
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return err
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}
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signal := make(chan *dbus.Signal)
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a.bus.Signal(signal)
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defer a.bus.RemoveSignal(signal)
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propertiesChangedMatchOptions := []dbus.MatchOption{dbus.WithMatchInterface("org.freedesktop.DBus.Properties")}
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a.bus.AddMatchSignal(propertiesChangedMatchOptions...)
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defer a.bus.RemoveMatchSignal(propertiesChangedMatchOptions...)
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newObjectMatchOptions := []dbus.MatchOption{dbus.WithMatchInterface("org.freedesktop.DBus.ObjectManager")}
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a.bus.AddMatchSignal(newObjectMatchOptions...)
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defer a.bus.RemoveMatchSignal(newObjectMatchOptions...)
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// Go through all connected devices and present the connected devices as
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// scan results. Also save the properties so that the full list of
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// properties is known on a PropertiesChanged signal. We can't present the
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// list of cached devices as scan results as devices may be cached for a
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// long time, long after they have moved out of range.
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var deviceList map[dbus.ObjectPath]map[string]map[string]dbus.Variant
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err = a.bluez.Call("org.freedesktop.DBus.ObjectManager.GetManagedObjects", 0).Store(&deviceList)
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if err != nil {
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return err
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}
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devices := make(map[dbus.ObjectPath]map[string]dbus.Variant)
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for path, v := range deviceList {
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device, ok := v["org.bluez.Device1"]
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if !ok {
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continue // not a device
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}
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if !strings.HasPrefix(string(path), string(a.adapter.Path())) {
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continue // not part of our adapter
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}
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if device["Connected"].Value().(bool) {
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callback(a, makeScanResult(device))
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select {
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case <-cancelChan:
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return nil
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default:
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}
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}
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devices[path] = device
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}
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// Instruct BlueZ to start discovering.
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err = a.adapter.Call("org.bluez.Adapter1.StartDiscovery", 0).Err
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if err != nil {
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return err
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}
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for {
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// Check whether the scan is stopped. This is necessary to avoid a race
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// condition between the signal channel and the cancelScan channel when
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// the callback calls StopScan() (no new callbacks may be called after
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// StopScan is called).
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select {
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case <-cancelChan:
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return a.adapter.Call("org.bluez.Adapter1.StopDiscovery", 0).Err
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default:
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}
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select {
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case sig := <-signal:
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// This channel receives anything that we watch for, so we'll have
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// to check for signals that are relevant to us.
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switch sig.Name {
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case "org.freedesktop.DBus.ObjectManager.InterfacesAdded":
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objectPath := sig.Body[0].(dbus.ObjectPath)
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interfaces := sig.Body[1].(map[string]map[string]dbus.Variant)
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rawprops, ok := interfaces["org.bluez.Device1"]
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if !ok {
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continue
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}
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devices[objectPath] = rawprops
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callback(a, makeScanResult(rawprops))
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case "org.freedesktop.DBus.Properties.PropertiesChanged":
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interfaceName := sig.Body[0].(string)
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if interfaceName != "org.bluez.Device1" {
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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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device, ok := devices[sig.Path]
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if !ok {
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// This shouldn't happen, but protect against it just in
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// case.
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continue
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}
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for k, v := range changes {
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device[k] = v
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}
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callback(a, makeScanResult(device))
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}
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case <-cancelChan:
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continue
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}
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}
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// unreachable
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}
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// StopScan stops any in-progress scan. It can be called from within a Scan
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// callback to stop the current scan. If no scan is in progress, an error will
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// be returned.
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func (a *Adapter) StopScan() error {
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if a.scanCancelChan == nil {
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return errNotScanning
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}
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close(a.scanCancelChan)
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a.scanCancelChan = nil
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return nil
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}
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// makeScanResult creates a ScanResult from a raw DBus device.
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func makeScanResult(props map[string]dbus.Variant) ScanResult {
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// Assume the Address property is well-formed.
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addr, _ := ParseMAC(props["Address"].Value().(string))
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// Create a list of UUIDs.
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var serviceUUIDs []UUID
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for _, uuid := range props["UUIDs"].Value().([]string) {
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// Assume the UUID is well-formed.
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parsedUUID, _ := ParseUUID(uuid)
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serviceUUIDs = append(serviceUUIDs, parsedUUID)
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}
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a := Address{MACAddress{MAC: addr}}
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a.SetRandom(props["AddressType"].Value().(string) == "random")
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var manufacturerData []ManufacturerDataElement
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if mdata, ok := props["ManufacturerData"].Value().(map[uint16]dbus.Variant); ok {
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for k, v := range mdata {
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manufacturerData = append(manufacturerData, ManufacturerDataElement{
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CompanyID: k,
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Data: v.Value().([]byte),
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})
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}
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}
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// Get optional properties.
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localName, _ := props["Name"].Value().(string)
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rssi, _ := props["RSSI"].Value().(int16)
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return ScanResult{
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RSSI: rssi,
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Address: a,
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AdvertisementPayload: &advertisementFields{
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AdvertisementFields{
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LocalName: localName,
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ServiceUUIDs: serviceUUIDs,
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ManufacturerData: manufacturerData,
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},
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},
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}
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}
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// Device is a connection to a remote peripheral.
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type Device struct {
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Address Address // the MAC address of the device
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device dbus.BusObject // bluez device interface
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adapter *Adapter // the adapter that was used to form this device connection
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}
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// Connect starts a connection attempt to the given peripheral device address.
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//
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// On Linux and Windows, the IsRandom part of the address is ignored.
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func (a *Adapter) Connect(address Address, params ConnectionParams) (Device, error) {
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devicePath := dbus.ObjectPath(string(a.adapter.Path()) + "/dev_" + strings.Replace(address.MAC.String(), ":", "_", -1))
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device := Device{
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Address: address,
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device: a.bus.Object("org.bluez", devicePath),
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adapter: a,
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}
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// Already start watching for property changes. We do this before reading
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// the Connected property below to avoid a race condition: if the device
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// were connected between the two calls the signal wouldn't be picked up.
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signal := make(chan *dbus.Signal)
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a.bus.Signal(signal)
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defer a.bus.RemoveSignal(signal)
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propertiesChangedMatchOptions := []dbus.MatchOption{dbus.WithMatchInterface("org.freedesktop.DBus.Properties")}
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a.bus.AddMatchSignal(propertiesChangedMatchOptions...)
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defer a.bus.RemoveMatchSignal(propertiesChangedMatchOptions...)
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// Read whether this device is already connected.
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connected, err := device.device.GetProperty("org.bluez.Device1.Connected")
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if err != nil {
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return Device{}, err
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}
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// Connect to the device, if not already connected.
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if !connected.Value().(bool) {
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// Start connecting (async).
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err := device.device.Call("org.bluez.Device1.Connect", 0).Err
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if err != nil {
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return Device{}, fmt.Errorf("bluetooth: failed to connect: %w", err)
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}
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// Wait until the device has connected.
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connectChan := make(chan struct{})
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go func() {
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for sig := range signal {
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switch sig.Name {
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case "org.freedesktop.DBus.Properties.PropertiesChanged":
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interfaceName := sig.Body[0].(string)
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if interfaceName != "org.bluez.Device1" {
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continue
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}
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if sig.Path != device.device.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 connected, ok := changes["Connected"].Value().(bool); ok && connected {
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close(connectChan)
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}
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}
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}
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}()
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<-connectChan
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}
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return device, nil
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}
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// Disconnect from the BLE device. This method is non-blocking and does not
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// wait until the connection is fully gone.
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func (d Device) Disconnect() error {
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// we don't call our cancel function here, instead we wait for the
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// property change in `watchForConnect` and cancel things then
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return d.device.Call("org.bluez.Device1.Disconnect", 0).Err
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}
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// RequestConnectionParams requests a different connection latency and timeout
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// of the given device connection. Fields that are unset will be left alone.
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// Whether or not the device will actually honor this, depends on the device and
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// on the specific parameters.
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//
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// On Linux, this call doesn't do anything because BlueZ doesn't support
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// changing the connection latency.
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func (d Device) RequestConnectionParams(params ConnectionParams) error {
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return nil
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}
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