private async Task ReadAttributeByType(GATTAttributeType attributeType, int timeoutMs)
{
Debug.WriteLine($"Discovering characteristics of type: {attributeType}");
_uuidOfAttributeBeingRead = attributeType;
await _bgApi.ATTClientReadByTypeAsync(
ConnectionHandle,
StartATTHandle,
EndATTHandle,
BitConverter.GetBytes((UInt16)_uuidOfAttributeBeingRead)
).ConfigureAwait(false);
using (var cancel = new CancellationTokenSource(timeoutMs)) {
try {
await _procedureCompletedWaitHandle
.WaitAsync(cancel.Token)
.ConfigureAwait(false);
_exceptionToRethrow?.Throw();
}
catch (OperationCanceledException) {
throw new TimeoutException($"Timeout occured while discovering characteristics of type: {attributeType}");
}
}
}
public override async Task <IReadOnlyCollection <Characteristic> > DiscoverCharacteristicsAsync(IList <byte[]> characteristicUUIDs = null, int timeoutMs = 10000)
{
try {
ThrowIfDisposed();
ThrowIfNotConnected();
if (State != ServiceState.Idle)
{
throw new Exception("Already busy discovering services");
}
State = ServiceState.DiscoveringCharacteristics;
ClearCharacteristics();
_bgApi.ATTClientAttributeValue += BGApi_ATTClientAttributeValue;
_bgApi.ATTClientProcedureCompleted += BGApi_ATTClientProcedureCompleted;
_clientConfigurationAttributeHandles.Clear();
// Discover characteristic declaration attributes
await ReadAttributeByType(
GATTAttributeType.CharacteristicUUID,
timeoutMs / 2
).ConfigureAwait(false);
if (!Characteristics.Any())
{
return(Characteristics);
}
// Discover client characteristic configuration attributes
await ReadAttributeByType(
GATTAttributeType.CharacteristicClientConfigurationUUID,
timeoutMs / 2
).ConfigureAwait(false);
// now determine which characteristic each client characteristic configuration handle belongs to
if ((_clientConfigurationAttributeHandles.Count == 1) && (Characteristics.Count == 1))
{
Characteristics.First().CharacteristicClientConfigurationHandle =
_clientConfigurationAttributeHandles.First();
}
else if ((_clientConfigurationAttributeHandles.Count > 0) && (Characteristics.Count > 0))
{
// sort the characteristic list by handle (ascending)
var charsAscending = Characteristics.OrderBy(
c => c.CharacteristicDeclarationHandle).ToArray();
// for each config handle, find the closest characteristic handle going up in values
foreach (var cfgHnd in _clientConfigurationAttributeHandles)
{
Characteristic charWhereCurrConfigHandleBelongs = null;
for (int i = 1; i < charsAscending.Length; i++)
{
var currCharHnd = charsAscending[i].CharacteristicDeclarationHandle;
var lastCharHnd = charsAscending[i - 1].CharacteristicDeclarationHandle;
if ((cfgHnd > lastCharHnd) && (cfgHnd < currCharHnd))
{
charWhereCurrConfigHandleBelongs = charsAscending[i - 1];
break;
}
}
if (charWhereCurrConfigHandleBelongs == null)
{
charWhereCurrConfigHandleBelongs = charsAscending.Last();
}
charWhereCurrConfigHandleBelongs.CharacteristicClientConfigurationHandle = cfgHnd;
}
}
}
finally {
_bgApi.ATTClientAttributeValue -= BGApi_ATTClientAttributeValue;
_bgApi.ATTClientProcedureCompleted -= BGApi_ATTClientProcedureCompleted;
_exceptionToRethrow = null;
_uuidOfAttributeBeingRead = 0;
_clientConfigurationAttributeHandles.Clear();
}
State = ServiceState.Idle;
var results = FilterCharacteristicsByUUIDs(Characteristics, characteristicUUIDs);
return(results);
}
