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GATTClient.swift
executable file
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GATTClient.swift
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//
// GATTClient.swift
// Bluetooth
//
// Created by Alsey Coleman Miller on 2/29/16.
// Copyright © 2016 PureSwift. All rights reserved.
//
import Foundation
public extension GATT {
public typealias Client = GATTClient
}
/// GATT Client
public final class GATTClient {
// MARK: - Properties
public var log: ((String) -> ())?
public var writePending: (() -> ())? {
get { return connection.writePending }
set { connection.writePending = newValue }
}
public private(set) var maximumTransmissionUnit: ATTMaximumTransmissionUnit {
get { return connection.maximumTransmissionUnit }
set { connection.maximumTransmissionUnit = newValue }
}
public let preferredMaximumTransmissionUnit: ATTMaximumTransmissionUnit
// Don't modify
@_versioned
internal private(set) var connection: ATTConnection
/// Whether the client is currently writing a long value.
internal private(set) var inLongWrite: Bool = false
/// Notications
internal private(set) var notifications = [UInt16: Notification]()
/// Indications
internal private(set) var indications = [UInt16: Notification]()
// MARK: - Initialization
public init(socket: L2CAPSocketProtocol,
maximumTransmissionUnit: ATT.MaximumTransmissionUnit = .default,
log: ((String) -> ())? = nil,
writePending: (() -> ())? = nil) {
self.connection = ATTConnection(socket: socket)
self.preferredMaximumTransmissionUnit = maximumTransmissionUnit
self.log = log
self.writePending = writePending
// setup notifications and indications
self.registerATTHandlers()
// queue MTU exchange if not default value
if maximumTransmissionUnit > .default {
self.exchangeMTU()
}
}
// MARK: - Methods
/// Performs the actual IO for recieving data.
public func read() throws -> Bool {
return try connection.read()
}
/// Performs the actual IO for sending data.
public func write() throws -> Bool {
return try connection.write()
}
// MARK: Requests
/// Discover All Primary Services
///
/// This sub-procedure is used by a client to discover all the primary services on a server.
/// 
///
/// - Parameter completion: The completion closure.
public func discoverAllPrimaryServices(completion: @escaping (GATTClientResponse<[Service]>) -> ()) {
/// The Attribute Protocol Read By Group Type Request shall be used with
/// the Attribute Type parameter set to the UUID for «Primary Service».
/// The Starting Handle shall be set to 0x0001 and the Ending Handle shall be set to 0xFFFF.
discoverServices(start: 0x0001, end: 0xFFFF, primary: true, completion: completion)
}
/// Discover Primary Service by Service UUID
///
/// This sub-procedure is used by a client to discover a specific primary service on a server
/// when only the Service UUID is known. The specific primary service may exist multiple times on a server.
/// The primary service being discovered is identified by the service UUID.
/// 
///
/// - Parameter uuid: The UUID of the service to find.
/// - Parameter completion: The completion closure.
public func discoverPrimaryServices(by uuid: BluetoothUUID,
completion: @escaping (GATTClientResponse<[Service]>) -> ()) {
// The Attribute Protocol Find By Type Value Request shall be used with the Attribute Type
// parameter set to the UUID for «Primary Service» and the Attribute Value set to the 16-bit
// Bluetooth UUID or 128-bit UUID for the specific primary service.
// The Starting Handle shall be set to 0x0001 and the Ending Handle shall be set to 0xFFFF.
discoverServices(uuid: uuid, start: 0x0001, end: 0xFFFF, primary: true, completion: completion)
}
/// Discover All Characteristics of a Service
///
/// This sub-procedure is used by a client to find all the characteristic declarations within
/// a service definition on a server when only the service handle range is known.
/// The service specified is identified by the service handle range.
/// 
///
/// - Parameter service: The service.
/// - Parameter completion: The completion closure.
public func discoverAllCharacteristics(of service: Service,
completion: @escaping (GATTClientResponse<[Characteristic]>) -> ()) {
// The Attribute Protocol Read By Type Request shall be used with the Attribute Type
// parameter set to the UUID for «Characteristic» The Starting Handle shall be set to
// starting handle of the specified service and the Ending Handle shall be set to the
// ending handle of the specified service.
discoverCharacteristics(service: service, completion: completion)
}
/// Discover Characteristics by UUID
///
/// This sub-procedure is used by a client to discover service characteristics on a server when
/// only the service handle ranges are known and the characteristic UUID is known.
/// The specific service may exist multiple times on a server.
/// The characteristic being discovered is identified by the characteristic UUID.
/// 
///
/// - Parameter service: The service of the characteristics to find.
/// - Parameter uuid: The UUID of the characteristics to find.
/// - Parameter completion: The completion closure.
public func discoverCharacteristics(of service: Service,
by uuid: BluetoothUUID,
completion: @escaping (GATTClientResponse<[Characteristic]>) -> ()) {
// The Attribute Protocol Read By Type Request is used to perform the beginning of the sub-procedure.
// The Attribute Type is set to the UUID for «Characteristic» and the Starting Handle and Ending Handle
// parameters shall be set to the service handle range.
discoverCharacteristics(uuid: uuid, service: service, completion: completion)
}
/// Read Characteristic Value
///
/// This sub-procedure is used to read a Characteristic Value from a server when the client knows
/// the Characteristic Value Handle.
///
/// 
public func readCharacteristic(_ characteristic: Characteristic,
completion: @escaping (GATTClientResponse<Data>) -> ()) {
// read value and try to read blob if too big
readAttributeValue(characteristic.handle.value, completion: completion)
}
/// Read Using Characteristic UUID
///
/// This sub-procedure is used to read a Characteristic Value from a server when the client
/// only knows the characteristic UUID and does not know the handle of the characteristic.
///
/// 
public func readCharacteristics(using uuid: BluetoothUUID,
handleRange: (start: UInt16, end: UInt16) = (.min, .max),
completion: @escaping (GATTClientResponse<[UInt16: Data]>) -> ()) {
precondition(handleRange.start < handleRange.end)
// The Attribute Protocol Read By Type Request is used to perform the sub-procedure.
// The Attribute Type is set to the known characteristic UUID and the Starting Handle and Ending Handle parameters
// shall be set to the range over which this read is to be performed. This is typically the handle range for the service in which the characteristic belongs.
let pdu = ATTReadByTypeRequest(startHandle: handleRange.start,
endHandle: handleRange.end,
attributeType: uuid)
let operation = ReadUsingUUIDOperation(uuid: uuid, completion: completion)
send(pdu) { [unowned self] in self.readByTypeResponse($0, operation: operation) }
}
/// Read Multiple Characteristic Values
///
/// This sub-procedure is used to read multiple Characteristic Values from a server when the client
/// knows the Characteristic Value Handles.
///
/// 
///
/// - Note: A client should not use this request for attributes when the Set Of Values parameter could be `(ATT_MTU–1)`
/// as it will not be possible to determine if the last attribute value is complete, or if it overflowed.
public func readCharacteristics(_ characteristics: [Characteristic], completion: @escaping (GATTClientResponse<Data>) -> ()) {
// The Attribute Protocol Read Multiple Request is used with the Set Of Handles parameter set to the Characteristic Value Handles.
// The Read Multiple Response returns the Characteristic Values in the Set Of Values parameter.
let handles = characteristics.map { $0.handle.value }
guard let pdu = ATTReadMultipleRequest(handles: handles)
else { fatalError("Must provide at least 2 characteristics") }
let operation = ReadMultipleOperation(characteristics: characteristics, completion: completion)
send(pdu) { [unowned self] in self.readMultipleResponse($0, operation: operation) }
}
/**
Write Characteristic
Uses the appropriate procecedure to write the characteristic value.
*/
public func writeCharacteristic(_ characteristic: Characteristic,
data: Data,
reliableWrites: Bool = true,
completion: ((GATTClientResponse<()>) -> ())?) {
writeAttribute(characteristic.handle.value,
data: data,
reliableWrites: reliableWrites,
completion: completion)
}
/**
Discover All Characteristic Descriptors
This sub-procedure is used by a client to find all the characteristic descriptor’s Attribute Handles and Attribute Types within a characteristic definition when only the characteristic handle range is known. The characteristic specified is identified by the characteristic handle range.
*/
public func discoverDescriptors(for characteristic: Characteristic,
service: (declaration: Service, characteristics: [Characteristic]),
completion: @escaping (GATTClientResponse<[Descriptor]>) -> ()) {
/**
The Attribute Protocol Find Information Request shall be used with the Starting Handle set
to the handle of the specified characteristic value + 1 and the Ending Handle set to the
ending handle of the specified characteristic.
*/
let start = characteristic.handle.value + 1
let end = endHandle(for: characteristic, service: service)
let operation = DescriptorDiscoveryOperation(start: start, end: end, completion: completion)
discoverDescriptors(operation: operation)
}
/// Read Characteristic Descriptor
///
/// This sub-procedure is used to read a characteristic descriptor from a server when the client knows
/// the characteristic descriptor declaration’s Attribute handle.
///
/// 
public func readDescriptor(_ descriptor: Descriptor,
completion: @escaping (GATTClientResponse<Data>) -> ()) {
/**
The Attribute Protocol Read Request is used for this sub-procedure. The Read Request is used with the Attribute Handle parameter set to the characteristic descriptor handle. The Read Response returns the characteristic descriptor value in the Attribute Value parameter.
An Error Response shall be sent by the server in response to the Read Request if insufficient authentication, insufficient authorization, insufficient encryption key size is used by the client, or if a read operation is not permitted on the Characteristic Value. The Error Code parameter is set accordingly.
*/
// read value and try to read blob if too big
readAttributeValue(descriptor.handle, completion: completion)
}
/**
Write Descriptor
Uses the appropriate procecedure to write the characteristic descriptor value.
*/
public func writeDescriptor(_ descriptor: Descriptor,
data: Data,
reliableWrites: Bool = true,
completion: ((GATTClientResponse<()>) -> ())?) {
writeAttribute(descriptor.handle,
data: data,
reliableWrites: reliableWrites,
completion: completion)
}
/**
Notifications
This sub-procedure is used when a server is configured to notify a Characteristic Value to a client without expecting any Attribute Protocol layer acknowledgment that the notification was successfully received.
*/
public func clientCharacteristicConfiguration(notification: Notification?,
indication: Notification?,
for characteristic: Characteristic,
descriptors: [GATTClient.Descriptor],
completion: @escaping (GATTClientResponse<()>) -> ()) {
guard let descriptor = descriptors.first(where: { $0.uuid == .clientCharacteristicConfiguration })
else { completion(.error(GATTClientError.clientCharacteristicConfigurationNotAllowed(characteristic))); return }
var clientConfiguration = GATTClientCharacteristicConfiguration()
if notification != nil {
clientConfiguration.configuration.insert(.notify)
}
if indication != nil {
clientConfiguration.configuration.insert(.indicate)
}
writeDescriptor(descriptor, data: clientConfiguration.data) { [unowned self] (response) in
switch response {
case .error:
break
case .value:
self.notifications[characteristic.handle.value] = notification
self.indications[characteristic.handle.value] = indication
}
completion(response)
}
}
// MARK: - Private Methods
@inline(__always)
private func registerATTHandlers() {
// value notifications / indications
connection.register { [weak self] in self?.notification($0) }
connection.register { [weak self] in self?.indication($0) }
}
@inline(__always)
private func send <Request: ATTProtocolDataUnit, Response> (_ request: Request, response: @escaping (ATTResponse<Response>) -> ()) {
let log = self.log
log?("Request: \(request)")
let callback: (AnyATTResponse) -> () = {
log?("Response: \($0.rawValue)")
response(ATTResponse<Response>($0))
}
let responseType: ATTProtocolDataUnit.Type = Response.self
guard let _ = connection.send(request, response: (callback, responseType))
else { fatalError("Could not add PDU to queue: \(request)") }
}
@inline(__always)
private func send <Request: ATTProtocolDataUnit> (_ request: Request) {
log?("Request: \(request)")
guard let _ = connection.send(request)
else { fatalError("Could not add PDU to queue: \(request)") }
}
internal func endHandle(for characteristic: Characteristic,
service: (declaration: Service, characteristics: [Characteristic])) -> UInt16 {
// calculate ending handle of characteristic
let end: UInt16
guard let index = service.characteristics.index(where: { $0.handle.declaration == characteristic.handle.declaration })
else { fatalError("Invalid characteristics \(service.characteristics.map { $0.uuid })") }
let nextIndex = index + 1
// get start handle of next characteristic
if nextIndex < service.characteristics.count {
let nextCharacteristic = service.characteristics[nextIndex]
end = nextCharacteristic.handle.declaration - 1
} else {
// use service end handle
end = service.declaration.end
}
return end
}
// MARK: Requests
private func exchangeMTU() {
let clientMTU = preferredMaximumTransmissionUnit
let pdu = ATTMaximumTransmissionUnitRequest(clientMTU: clientMTU.rawValue)
send(pdu) { [unowned self] in self.exchangeMTUResponse($0) }
}
private func discoverServices(uuid: BluetoothUUID? = nil,
start: UInt16 = 0x0001,
end: UInt16 = 0xffff,
primary: Bool = true,
completion: @escaping (GATTClientResponse<[Service]>) -> ()) {
let serviceType = GATT.UUID(primaryService: primary)
let operation = DiscoveryOperation<Service>(uuid: uuid,
start: start,
end: end,
type: serviceType,
completion: completion)
if let uuid = uuid {
let pdu = ATTFindByTypeRequest(startHandle: start,
endHandle: end,
attributeType: serviceType.rawValue,
attributeValue: uuid.littleEndian.data)
send(pdu) { [unowned self] in self.findByTypeResponse($0, operation: operation) }
} else {
let pdu = ATTReadByGroupTypeRequest(startHandle: start,
endHandle: end,
type: serviceType.uuid)
send(pdu) { [unowned self] in self.readByGroupTypeResponse($0, operation: operation) }
}
}
private func discoverCharacteristics(uuid: BluetoothUUID? = nil,
service: Service,
completion: @escaping (GATTClientResponse<[Characteristic]>) -> ()) {
let attributeType = GATT.UUID.characteristic
let operation = DiscoveryOperation<Characteristic>(uuid: uuid,
start: service.handle,
end: service.end,
type: attributeType,
completion: completion)
let pdu = ATTReadByTypeRequest(startHandle: service.handle,
endHandle: service.end,
attributeType: attributeType.uuid)
send(pdu) { [unowned self] in self.readByTypeResponse($0, operation: operation) }
}
private func discoverDescriptors(operation: DescriptorDiscoveryOperation) {
assert(operation.start <= operation.end, "Invalid range")
let pdu = ATTFindInformationRequest(startHandle: operation.start, endHandle: operation.end)
send(pdu) { [unowned self] in self.findInformationResponse($0, operation: operation) }
}
/// Read Characteristic Value
///
/// This sub-procedure is used to read a Characteristic Value from a server when the client knows
/// the Characteristic Value Handle.
///
/// 
private func readAttributeValue(_ handle: UInt16, completion: @escaping (GATTClientResponse<Data>) -> ()) {
// The Attribute Protocol Read Request is used with the
// Attribute Handle parameter set to the Characteristic Value Handle.
// The Read Response returns the Characteristic Value in the Attribute Value parameter.
// read value and try to read blob if too big
let pdu = ATTReadRequest(handle: handle)
let operation = ReadOperation(handle: handle, completion: completion)
send(pdu) { [unowned self] in self.readResponse($0, operation: operation) }
}
/// Read Long Characteristic Value
///
/// This sub-procedure is used to read a Characteristic Value from a server when the client knows
/// the Characteristic Value Handle and the length of the Characteristic Value is longer than can
/// be sent in a single Read Response Attribute Protocol message.
///
/// 
@inline(__always)
private func readLongAttributeValue(_ operation: ReadOperation) {
// The Attribute Protocol Read Blob Request is used to perform this sub-procedure.
// The Attribute Handle shall be set to the Characteristic Value Handle of the Characteristic Value to be read.
// The Value Offset parameter shall be the offset within the Characteristic Value to be read. To read the
// complete Characteristic Value the offset should be set to 0x00 for the first Read Blob Request.
// The offset for subsequent Read Blob Requests is the next octet that has yet to be read.
// The Read Blob Request is repeated until the Read Blob Response’s Part Attribute Value parameter is shorter than (ATT_MTU-1).
let pdu = ATTReadBlobRequest(handle: operation.handle,
offset: operation.offset)
send(pdu) { [unowned self] in self.readBlobResponse($0, operation: operation) }
}
private func writeAttribute(_ handle: UInt16,
data: Data,
reliableWrites: Bool,
completion: ((GATTClientResponse<()>) -> ())?) {
// short value
if data.count <= Int(maximumTransmissionUnit.rawValue) - ATTWriteRequest.length { // ATT_MTU - 3
if let completion = completion {
writeAttributeValue(handle,
data: data,
completion: completion)
} else {
writeAttributeCommand(handle,
data: data)
}
} else {
let completion = completion ?? { _ in }
writeLongAttributeValue(handle,
data: data,
reliableWrites: reliableWrites,
completion: completion)
}
}
private func writeAttributeCommand(_ attribute: UInt16, data: Data) {
let data = Data(data.prefix(Int(maximumTransmissionUnit.rawValue) - 3))
let pdu = ATTWriteCommand(handle: attribute, value: data)
send(pdu)
}
/// Write attribute request.
private func writeAttributeValue(_ attribute: UInt16,
data: Data,
completion: @escaping (GATTClientResponse<()>) -> ()) {
let data = Data(data.prefix(Int(maximumTransmissionUnit.rawValue) - ATTWriteRequest.length))
let pdu = ATTWriteRequest(handle: attribute, value: data)
send(pdu) { [unowned self] in self.writeResponse($0, completion: completion) }
}
private func writeLongAttributeValue(_ attribute: UInt16,
data: Data,
reliableWrites: Bool = false,
completion: @escaping (GATTClientResponse<()>) -> ()) {
// The Attribute Protocol Prepare Write Request and Execute Write Request are used to perform this sub-procedure.
// The Attribute Handle parameter shall be set to the Characteristic Value Handle of the Characteristic Value to be written.
// The Part Attribute Value parameter shall be set to the part of the Attribute Value that is being written.
// The Value Offset parameter shall be the offset within the Characteristic Value to be written.
// To write the complete Characteristic Value the offset should be set to 0x0000 for the first Prepare Write Request.
// The offset for subsequent Prepare Write Requests is the next octet that has yet to be written.
// The Prepare Write Request is repeated until the complete Characteristic Value has been transferred,
// after which an Executive Write Request is used to write the complete value.
guard inLongWrite == false
else { completion(.error(GATTClientError.inLongWrite)); return }
let firstValuePart = Data(data.prefix(Int(maximumTransmissionUnit.rawValue) - ATTPrepareWriteRequest.length))
let pdu = ATTPrepareWriteRequest(handle: attribute,
offset: 0x00,
partValue: firstValuePart)
let operation = WriteOperation(handle: attribute,
data: data,
reliableWrites: reliableWrites,
lastRequest: pdu,
completion: completion)
send(pdu) { [unowned self] in self.prepareWriteResponse($0, operation: operation) }
}
/**
Signed Write Without Response
This sub-procedure is used to write a Characteristic Value to a server when the client knows the Characteristic Value Handle and the ATT Bearer is not encrypted. This sub-procedure shall only be used if the Characteristic Properties authenticated bit is enabled and the client and server device share a bond.
If the authenticated Characteristic Value that is written is the wrong size, has an invalid value as defined by the profile, or the signed value does not authenticate the client, then the write shall not succeed and no error shall be gener- ated by the server.
- Note: On BR/EDR, the ATT Bearer is always encrypted, due to the use of Security Mode 4, therefore this sub-procedure shall not be used.
*/
private func writeSignedCharacteristicCommand(_ characteristic: Characteristic, data: Data) {
// This sub-procedure only writes the first (ATT_MTU – 15) octets of an Attribute Value.
// This sub-procedure cannot be used to write a long Attribute.
// The Attribute Protocol Write Command is used for this sub-procedure.
// The Attribute Handle parameter shall be set to the Characteristic Value Handle.
// The Attribute Value parameter shall be set to the new Characteristic Value authenticated by signing the value.
// If a connection is already encrypted with LE security mode 1, level 2 or level 3 as defined in [Vol 3] Part C,
// Section 10.2 then, a Write Without Response as defined in Section 4.9.1 shall be used instead of
// a Signed Write Without Response.
let data = Data(data.prefix(Int(maximumTransmissionUnit.rawValue) - 15))
// TODO: Sign Data
let pdu = ATTWriteCommand(handle: characteristic.handle.value, value: data)
send(pdu)
}
// MARK: - Callbacks
private func exchangeMTUResponse(_ response: ATTResponse<ATTMaximumTransmissionUnitResponse>) {
switch response {
case let .error(error):
log?("Could not exchange MTU: \(error)")
case let .value(pdu):
let clientMTU = preferredMaximumTransmissionUnit
let finalMTU = ATTMaximumTransmissionUnit(server: pdu.serverMTU, client: clientMTU.rawValue)
log?("MTU Exchange (\(clientMTU) -> \(finalMTU))")
self.maximumTransmissionUnit = finalMTU
}
}
private func readByGroupTypeResponse(_ response: ATTResponse<ATTReadByGroupTypeResponse>,
operation: DiscoveryOperation<Service>) {
// Read By Group Type Response returns a list of Attribute Handle, End Group Handle, and Attribute Value tuples
// corresponding to the services supported by the server. Each Attribute Value contained in the response is the
// Service UUID of a service supported by the server. The Attribute Handle is the handle for the service declaration.
// The End Group Handle is the handle of the last attribute within the service definition.
// The Read By Group Type Request shall be called again with the Starting Handle set to one greater than the
// last End Group Handle in the Read By Group Type Response.
switch response {
case let .error(errorResponse):
operation.error(errorResponse)
case let .value(pdu):
// store PDU values
for serviceData in pdu.attributeData {
guard let littleEndianServiceUUID = BluetoothUUID(data: serviceData.value)
else { operation.completion(.error(Error.invalidResponse(pdu))); return }
let serviceUUID = BluetoothUUID(littleEndian: littleEndianServiceUUID)
let service = Service(uuid: serviceUUID,
type: operation.type,
handle: serviceData.attributeHandle,
end: serviceData.endGroupHandle)
operation.foundData.append(service)
}
// get more if possible
let lastEnd = pdu.attributeData.last?.endGroupHandle ?? 0x00
// prevent infinite loop
guard lastEnd >= operation.start
else { operation.completion(.error(Error.invalidResponse(pdu))); return }
guard lastEnd < .max // End of database
else { operation.success(); return }
operation.start = lastEnd + 1
if lastEnd < operation.end {
let pdu = ATTReadByGroupTypeRequest(startHandle: operation.start,
endHandle: operation.end,
type: operation.type.uuid)
send(pdu) { [unowned self] in self.readByGroupTypeResponse($0, operation: operation) }
} else {
operation.success()
}
}
}
private func findByTypeResponse(_ response: ATTResponse<ATTFindByTypeResponse>, operation: DiscoveryOperation<Service>) {
// Find By Type Value Response returns a list of Attribute Handle ranges.
// The Attribute Handle range is the starting handle and the ending handle of the service definition.
// If the Attribute Handle range for the Service UUID being searched is returned and the End Found Handle
// is not 0xFFFF, the Find By Type Value Request may be called again with the Starting Handle set to one
// greater than the last Attribute Handle range in the Find By Type Value Response.
switch response {
case let .error(errorResponse):
operation.error(errorResponse)
case let .value(pdu):
guard let serviceUUID = operation.uuid
else { fatalError("Should have UUID specified") }
// pre-allocate array
operation.foundData.reserveCapacity(operation.foundData.count + pdu.handlesInformationList.count)
// store PDU values
for serviceData in pdu.handlesInformationList {
let service = Service(uuid: serviceUUID,
type: operation.type,
handle: serviceData.foundAttribute,
end: serviceData.groupEnd)
operation.foundData.append(service)
}
// get more if possible
let lastEnd = pdu.handlesInformationList.last?.groupEnd ?? 0x00
guard lastEnd < .max // End of database
else { operation.success(); return }
operation.start = lastEnd + 1
// need to continue scanning
if lastEnd < operation.end {
let pdu = ATTFindByTypeRequest(startHandle: operation.start,
endHandle: operation.end,
attributeType: operation.type.rawValue,
attributeValue: serviceUUID.littleEndian.data)
send(pdu) { [unowned self] in self.findByTypeResponse($0, operation: operation) }
} else {
operation.success()
}
}
}
private func findInformationResponse(_ response: ATTResponse<ATTFindInformationResponse>,
operation: DescriptorDiscoveryOperation) {
/**
Two possible responses can be sent from the server for the Find Information Request: Find Information Response and Error Response.
Error Response is returned if an error occurred on the server.
Find Information Response returns a list of Attribute Handle and Attribute Value pairs corresponding to the characteristic descriptors in the characteristic definition. The Attribute Handle is the handle for the characteristic descriptor declaration. The Attribute Value is the Characteristic Descriptor UUID.
The Find Information Request shall be called again with the Starting Handle set to one greater than the last Attribute Handle in the Find Information Response.
The sub-procedure is complete when the Error Response is received and the Error Code is set to Attribute Not Found or the Find Information Response has an Attribute Handle that is equal to the Ending Handle of the request.
It is permitted to end the sub-procedure early if a desired Characteristic Descriptor is found prior to discovering all the characteristic descriptors of the specified characteristic.
*/
switch response {
case let .error(errorResponse):
operation.error(errorResponse)
case let .value(pdu):
// pre-allocate array
operation.foundDescriptors.reserveCapacity(operation.foundDescriptors.count + pdu.data.count)
let foundData: [Descriptor]
switch pdu.attributeData {
case let .bit16(values):
foundData = values.map { Descriptor(uuid: .bit16($0.uuid), handle: $0.handle) }
case let .bit128(values):
foundData = values.map { Descriptor(uuid: .bit128($0.uuid), handle: $0.handle) }
}
operation.foundDescriptors += foundData
// get more if possible
let lastHandle = foundData.last?.handle ?? 0x00
// prevent infinite loop
guard lastHandle >= operation.start
else { operation.completion(.error(Error.invalidResponse(pdu))); return }
guard lastHandle < .max // End of database
else { operation.success(); return }
let start = lastHandle + 1
// need to continue discovery
if lastHandle != 0, start < operation.end {
operation.start = start
discoverDescriptors(operation: operation)
} else {
// end of service
operation.success()
}
}
}
private func readByTypeResponse(_ response: ATTResponse<ATTReadByTypeResponse>,
operation: DiscoveryOperation<Characteristic>) {
typealias DeclarationAttribute = GATTDatabase.CharacteristicDeclarationAttribute
typealias Attribute = GATTDatabase.Attribute
// Read By Type Response returns a list of Attribute Handle and Attribute Value pairs corresponding to the
// characteristics in the service definition. The Attribute Handle is the handle for the characteristic declaration.
// The Attribute Value is the Characteristic Properties, Characteristic Value Handle and Characteristic UUID.
// The Read By Type Request shall be called again with the Starting Handle set to one greater than the last
// Attribute Handle in the Read By Type Response.
switch response {
case let .error(errorResponse):
operation.error(errorResponse)
case let .value(pdu):
// pre-allocate array
operation.foundData.reserveCapacity(operation.foundData.count + pdu.data.count)
// parse pdu data
for characteristicData in pdu.attributeData {
let handle = characteristicData.handle
let attribute = Attribute(handle: handle,
uuid: .characteristic,
value: Data(characteristicData.value),
permissions: [.read])
guard let declaration = DeclarationAttribute(attribute: attribute)
else { operation.completion(.error(Error.invalidResponse(pdu))); return }
let characteristic = Characteristic(uuid: declaration.uuid,
properties: declaration.properties,
handle: (handle, declaration.valueHandle))
operation.foundData.append(characteristic)
// if we specified a UUID to be searched,
// then call completion if it matches
if let operationUUID = operation.uuid {
guard characteristic.uuid != operationUUID
else { operation.success(); return }
}
}
// get more if possible
let lastEnd = pdu.attributeData.last?.handle ?? 0x00
// prevent infinite loop
guard lastEnd >= operation.start
else { operation.completion(.error(Error.invalidResponse(pdu))); return }
operation.start = lastEnd + 1
// need to continue discovery
if lastEnd != 0, operation.start < operation.end {
let pdu = ATTReadByTypeRequest(startHandle: operation.start,
endHandle: operation.end,
attributeType: operation.type.uuid)
send(pdu) { [unowned self] in self.readByTypeResponse($0, operation: operation) }
} else {
// end of service
operation.success()
}
}
}
/// Read Characteristic (or Descriptor) Value Response
private func readResponse(_ response: ATTResponse<ATTReadResponse>, operation: ReadOperation) {
// The Read Response only contains a Characteristic Value that is less than or equal to (ATT_MTU – 1) octets in length.
// If the Characteristic Value is greater than (ATT_MTU – 1) octets in length, the Read Long Characteristic Value procedure
// may be used if the rest of the Characteristic Value is required.
switch response {
case let .error(error):
operation.error(error)
case let .value(pdu):
operation.data = pdu.attributeValue
// short value
if pdu.attributeValue.count < (Int(maximumTransmissionUnit.rawValue) - 1) {
operation.success()
} else {
// read blob
readLongAttributeValue(operation)
}
}
}
/// Read Blob Response
private func readBlobResponse(_ response: ATTResponse<ATTReadBlobResponse>, operation: ReadOperation) {
// For each Read Blob Request a Read Blob Response is received with a portion of the Characteristic Value contained in the Part Attribute Value parameter.
switch response {
case let .error(error):
operation.error(error)
case let .value(pdu):
operation.data += pdu.partAttributeValue
// short value
if pdu.partAttributeValue.count < (Int(maximumTransmissionUnit.rawValue) - 1) {
operation.success()
} else {
// read blob
readLongAttributeValue(operation)
}
}
}
private func readMultipleResponse(_ response: ATTResponse<ATTReadMultipleResponse>, operation: ReadMultipleOperation) {
switch response {
case let .error(error):
operation.error(error)
case let .value(pdu):
operation.success(pdu.values)