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gap_windows.go
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gap_windows.go
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package bluetooth
import (
"fmt"
"unsafe"
"github.com/go-ole/go-ole"
"github.com/saltosystems/winrt-go"
"github.com/saltosystems/winrt-go/windows/devices/bluetooth"
"github.com/saltosystems/winrt-go/windows/devices/bluetooth/advertisement"
"github.com/saltosystems/winrt-go/windows/devices/bluetooth/genericattributeprofile"
"github.com/saltosystems/winrt-go/windows/foundation"
"github.com/saltosystems/winrt-go/windows/storage/streams"
)
// Address contains a Bluetooth MAC address.
type Address struct {
MACAddress
}
// Scan starts a BLE scan. It is stopped by a call to StopScan. A common pattern
// is to cancel the scan when a particular device has been found.
func (a *Adapter) Scan(callback func(*Adapter, ScanResult)) (err error) {
if a.watcher != nil {
// Cannot scan more than once: which one should ScanStop()
// stop?
return errScanning
}
a.watcher, err = advertisement.NewBluetoothLEAdvertisementWatcher()
if err != nil {
return
}
defer func() {
_ = a.watcher.Release()
a.watcher = nil
}()
// Listen for incoming BLE advertisement packets.
// We need a TypedEventHandler<TSender, TResult> to listen to events, but since this is a parameterized delegate
// its GUID depends on the classes used as sender and result, so we need to compute it:
// TypedEventHandler<BluetoothLEAdvertisementWatcher, BluetoothLEAdvertisementReceivedEventArgs>
eventReceivedGuid := winrt.ParameterizedInstanceGUID(
foundation.GUIDTypedEventHandler,
advertisement.SignatureBluetoothLEAdvertisementWatcher,
advertisement.SignatureBluetoothLEAdvertisementReceivedEventArgs,
)
handler := foundation.NewTypedEventHandler(ole.NewGUID(eventReceivedGuid), func(instance *foundation.TypedEventHandler, sender, arg unsafe.Pointer) {
args := (*advertisement.BluetoothLEAdvertisementReceivedEventArgs)(arg)
result := getScanResultFromArgs(args)
callback(a, result)
})
defer handler.Release()
token, err := a.watcher.AddReceived(handler)
if err != nil {
return
}
defer a.watcher.RemoveReceived(token)
// Wait for when advertisement has stopped by a call to StopScan().
// Advertisement doesn't seem to stop right away, there is an
// intermediate Stopping state.
stoppingChan := make(chan struct{})
// TypedEventHandler<BluetoothLEAdvertisementWatcher, BluetoothLEAdvertisementWatcherStoppedEventArgs>
eventStoppedGuid := winrt.ParameterizedInstanceGUID(
foundation.GUIDTypedEventHandler,
advertisement.SignatureBluetoothLEAdvertisementWatcher,
advertisement.SignatureBluetoothLEAdvertisementWatcherStoppedEventArgs,
)
stoppedHandler := foundation.NewTypedEventHandler(ole.NewGUID(eventStoppedGuid), func(_ *foundation.TypedEventHandler, _, _ unsafe.Pointer) {
// Note: the args parameter has an Error property that should
// probably be checked, but I'm not sure when stopping the
// advertisement watcher could ever result in an error (except
// for bugs).
close(stoppingChan)
})
defer stoppedHandler.Release()
token, err = a.watcher.AddStopped(stoppedHandler)
if err != nil {
return
}
defer a.watcher.RemoveStopped(token)
err = a.watcher.Start()
if err != nil {
return err
}
// Wait until advertisement has stopped, and finish.
<-stoppingChan
return nil
}
func getScanResultFromArgs(args *advertisement.BluetoothLEAdvertisementReceivedEventArgs) ScanResult {
// parse bluetooth address
addr, _ := args.GetBluetoothAddress()
adr := Address{}
for i := range adr.MAC {
adr.MAC[i] = byte(addr)
addr >>= 8
}
sigStrength, _ := args.GetRawSignalStrengthInDBm()
result := ScanResult{
RSSI: sigStrength,
Address: adr,
}
var manufacturerData map[uint16][]byte = make(map[uint16][]byte)
if winAdv, err := args.GetAdvertisement(); err == nil && winAdv != nil {
vector, _ := winAdv.GetManufacturerData()
size, _ := vector.GetSize()
for i := uint32(0); i < size; i++ {
element, _ := vector.GetAt(i)
manData := (*advertisement.BluetoothLEManufacturerData)(element)
companyID, _ := manData.GetCompanyId()
buffer, _ := manData.GetData()
manufacturerData[companyID] = bufferToSlice(buffer)
}
}
// Note: the IsRandom bit is never set.
advertisement, _ := args.GetAdvertisement()
localName, _ := advertisement.GetLocalName()
result.AdvertisementPayload = &advertisementFields{
AdvertisementFields{
LocalName: localName,
ManufacturerData: manufacturerData,
},
}
return result
}
func bufferToSlice(buffer *streams.IBuffer) []byte {
dataReader, _ := streams.FromBuffer(buffer)
defer dataReader.Release()
bufferSize, _ := buffer.GetLength()
data, _ := dataReader.ReadBytes(bufferSize)
return data
}
// StopScan stops any in-progress scan. It can be called from within a Scan
// callback to stop the current scan. If no scan is in progress, an error will
// be returned.
func (a *Adapter) StopScan() error {
if a.watcher == nil {
return errNotScanning
}
return a.watcher.Stop()
}
// Device is a connection to a remote peripheral.
type Device struct {
device *bluetooth.BluetoothLEDevice
session *genericattributeprofile.GattSession
}
// Connect starts a connection attempt to the given peripheral device address.
//
// On Linux and Windows, the IsRandom part of the address is ignored.
func (a *Adapter) Connect(addresser Addresser, params ConnectionParams) (*Device, error) {
address := addresser.(Address).MACAddress
var winAddr uint64
for i := range address.MAC {
winAddr += uint64(address.MAC[i]) << (8 * i)
}
// IAsyncOperation<BluetoothLEDevice>
bleDeviceOp, err := bluetooth.FromBluetoothAddressAsync(winAddr)
if err != nil {
return nil, err
}
// We need to pass the signature of the parameter returned by the async operation:
// IAsyncOperation<BluetoothLEDevice>
if err := awaitAsyncOperation(bleDeviceOp, bluetooth.SignatureBluetoothLEDevice); err != nil {
return nil, fmt.Errorf("error connecting to device: %w", err)
}
res, err := bleDeviceOp.GetResults()
if err != nil {
return nil, err
}
// The returned BluetoothLEDevice is set to null if FromBluetoothAddressAsync can't find the device identified by bluetoothAddress
if uintptr(res) == 0x0 {
return nil, fmt.Errorf("device with the given address was not found")
}
bleDevice := (*bluetooth.BluetoothLEDevice)(res)
// Creating a BluetoothLEDevice object by calling this method alone doesn't (necessarily) initiate a connection.
// To initiate a connection, we need to set GattSession.MaintainConnection to true.
dID, err := bleDevice.GetBluetoothDeviceId()
if err != nil {
return nil, err
}
// Windows does not support explicitly connecting to a device.
// Instead it has the concept of a GATT session that is owned
// by the calling program.
gattSessionOp, err := genericattributeprofile.FromDeviceIdAsync(dID) // IAsyncOperation<GattSession>
if err != nil {
return nil, err
}
if err := awaitAsyncOperation(gattSessionOp, genericattributeprofile.SignatureGattSession); err != nil {
return nil, fmt.Errorf("error getting gatt session: %w", err)
}
gattRes, err := gattSessionOp.GetResults()
if err != nil {
return nil, err
}
newSession := (*genericattributeprofile.GattSession)(gattRes)
// This keeps the device connected until we set maintain_connection = False.
if err := newSession.SetMaintainConnection(true); err != nil {
return nil, err
}
return &Device{bleDevice, newSession}, nil
}
// Disconnect from the BLE device. This method is non-blocking and does not
// wait until the connection is fully gone.
func (d *Device) Disconnect() error {
defer d.device.Release()
defer d.session.Release()
if err := d.session.Close(); err != nil {
return err
}
if err := d.device.Close(); err != nil {
return err
}
return nil
}