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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef DEVICE_BLUETOOTH_BLUETOOTH_GATT_DESCRIPTOR_H_
#define DEVICE_BLUETOOTH_BLUETOOTH_GATT_DESCRIPTOR_H_
#include <string>
#include "base/functional/callback.h"
#include "base/functional/callback_forward.h"
#include "device/bluetooth/bluetooth_export.h"
#include "device/bluetooth/bluetooth_gatt_characteristic.h"
#include "device/bluetooth/bluetooth_gatt_service.h"
#include "device/bluetooth/public/cpp/bluetooth_uuid.h"
namespace device {
// BluetoothGattDescriptor represents a local or remote GATT characteristic
// descriptor. A GATT characteristic descriptor provides further information
// about a characteristic's value. They can be used to describe the
// characteristic's features or to control certain behaviors.
class DEVICE_BLUETOOTH_EXPORT BluetoothGattDescriptor {
public:
// The ErrorCallback is used by methods to asynchronously report errors.
using ErrorCallback =
base::OnceCallback<void(BluetoothGattService::GattErrorCode)>;
BluetoothGattDescriptor(const BluetoothGattDescriptor&) = delete;
BluetoothGattDescriptor& operator=(const BluetoothGattDescriptor&) = delete;
// The Bluetooth Specification declares several predefined descriptors that
// profiles can use. The following are definitions for the list of UUIDs
// and descriptions of the characteristic descriptors that they represent.
// Possible values for and further information on each descriptor can be found
// in Core v4.0, Volume 3, Part G, Section 3.3.3. All of these descriptors are
// optional and may not be present for a given characteristic.
// The "Characteristic Extended Properties" descriptor. This defines
// additional "Characteristic Properties" which cannot fit into the allocated
// single octet property field of a characteristic. The value is a bit field
// and the two predefined bits, as per Bluetooth Core Specification v4.0, are:
//
// - Reliable Write: 0x0001
// - Writable Auxiliaries: 0x0002
//
static const BluetoothUUID& CharacteristicExtendedPropertiesUuid();
// The "Characteristic User Description" descriptor defines a UTF-8 string of
// variable size that is a user textual description of the associated
// characteristic's value. There can be only one instance of this descriptor
// per characteristic. This descriptor can be written to if the "Writable
// Auxiliaries" bit of the Characteristic Properties (via the "Characteristic
// Extended Properties" descriptor) has been set.
static const BluetoothUUID& CharacteristicUserDescriptionUuid();
// The "Client Characteristic Configuration" descriptor defines how the
// characteristic may be configured by a specific client. A server-side
// instance of this descriptor exists for each client that has bonded with
// the server and the value can be read and written by that client only. As
// of Core v4.0, this descriptor is used by clients to set up notifications
// and indications from a characteristic. The value is a bit field and the
// predefined bits are:
//
// - Default: 0x0000
// - Notification: 0x0001
// - Indication: 0x0002
//
static const BluetoothUUID& ClientCharacteristicConfigurationUuid();
// The "Server Characteristic Configuration" descriptor defines how the
// characteristic may be configured for the server. There is one instance
// of this descriptor for all clients and setting the value of this descriptor
// affects its configuration for all clients. As of Core v4.0, this descriptor
// is used to set up the server to broadcast the characteristic value if
// advertising resources are available. The value is a bit field and the
// predefined bits are:
//
// - Default: 0x0000
// - Broadcast: 0x0001
//
static const BluetoothUUID& ServerCharacteristicConfigurationUuid();
// The "Characteristic Presentation Format" declaration defines the format of
// the Characteristic Value. The value is composed of 7 octets which are
// divided into groups that represent different semantic meanings. For a
// detailed description of how the value of this descriptor should be
// interpreted, refer to Core v4.0, Volume 3, Part G, Section 3.3.3.5. If more
// than one declaration of this descriptor exists for a characteristic, then a
// "Characteristic Aggregate Format" descriptor must also exist for that
// characteristic.
static const BluetoothUUID& CharacteristicPresentationFormatUuid();
// The "Characteristic Aggregate Format" descriptor defines the format of an
// aggregated characteristic value. In GATT's underlying protocol, ATT, each
// attribute is identified by a handle that is unique for the hosting server.
// Multiple characteristics can share the same instance(s) of a
// "Characteristic Presentation Format" descriptor. The value of the
// "Characteristic Aggregate Format" descriptor contains a list of handles
// that each refer to a "Characteristic Presentation Format" descriptor that
// is used by that characteristic. Hence, exactly one instance of this
// descriptor must exist if more than one "Characteristic Presentation Format"
// descriptors exist for a characteristic.
//
// Applications that are using the device::Bluetooth API do not have access to
// the underlying handles and shouldn't use this descriptor to determine which
// "Characteristic Presentation Format" descriptors belong to a
// characteristic.
// The API will construct a BluetoothGattDescriptor object for each instance
// of "Characteristic Presentation Format" descriptor per instance of
// BluetoothRemoteGattCharacteristic that represents a remote characteristic.
// Similarly for local characteristics, implementations DO NOT need to create
// an instance of BluetoothGattDescriptor for this descriptor as this will be
// handled by the subsystem.
static const BluetoothUUID& CharacteristicAggregateFormatUuid();
// Identifier used to uniquely identify a GATT descriptor object. This is
// different from the descriptor UUID: while multiple descriptors with the
// same UUID can exist on a Bluetooth device, the identifier returned from
// this method is unique among all descriptors on the adapter. The contents of
// the identifier are platform specific.
virtual std::string GetIdentifier() const = 0;
// The Bluetooth-specific UUID of the characteristic descriptor.
virtual BluetoothUUID GetUUID() const = 0;
// Returns the bitmask of characteristic descriptor attribute permissions.
virtual BluetoothGattCharacteristic::Permissions GetPermissions() const = 0;
protected:
BluetoothGattDescriptor();
virtual ~BluetoothGattDescriptor();
};
} // namespace device
#endif // DEVICE_BLUETOOTH_BLUETOOTH_GATT_DESCRIPTOR_H_
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