device/bluetooth: Add abstract API definition for BluetoothGattDescriptor.

device/bluetooth/bluetooth_gatt_characteristic.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DEVICE_BLUETOOTH_GATT_CHARACTERISTIC_H_
 #define DEVICE_BLUETOOTH_GATT_CHARACTERISTIC_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 77 matching lines @@
         const std::vector<uint8>& value) {}
 
     // Called when the descriptors that are associated with |characteristic|
     // have changed.
     virtual void DescriptorsChanged(
         BluetoothGattCharacteristic* characteristic,
         const std::vector<BluetoothGattDescriptor*>& descriptors) {}
   };
 
   // The ErrorCallback is used by methods to asynchronously report errors.
-  typedef base::Callback<const std::string&> ErrorCallback;
+  typedef base::Callback<void(const std::string&)> ErrorCallback;
+
+  // The ValueCallback is used to return the value of a remote characteristic
+  // upon a read request.
+  typedef base::Callback<void(const std::vector<uint8>&)> ValueCallback;
 
   // Adds and removes observers for events on this GATT characteristic. If
   // monitoring multiple characteristics, check the |characteristic| parameter
   // of observer methods to determine which characteristic is issuing the event.
   virtual void AddObserver(Observer* observer) = 0;
   virtual void RemoveObserver(Observer* observer) = 0;
 
   // Constructs a BluetoothGattCharacteristic that can be associated with a
   // local GATT service when the adapter is in the peripheral role. To
   // associate the returned characteristic with a service, add it to a local
@@ skipping 44 matching lines @@
   // any notifications and indications that have been configured. This method
   // can be used in place of, and in conjunction with,
   // BluetoothGattService::Delegate methods to send updates to remote devices,
   // or simply to set update the cached value for read requests without having
   // to implement the delegate methods.
   //
   // This method only makes sense for local characteristics and does nothing and
   // returns false if this instance represents a remote characteristic.
   virtual bool UpdateValue(const std::vector<uint8>& value) = 0;
 
+  // Sends a read request to a remote characteristic to read its value.
+  // |callback| is called to return the read value on success and
+  // |error_callback| is called for failures.
+  virtual void ReadRemoteCharacteristic(
+      const ValueCallback& callback,
+      const ErrorCallback& error_callback) = 0;
+
   // Sends a write request to a remote characteristic, to modify the
   // characteristic's value starting at offset |offset| with the new value
   // |new_value|. |callback| is called to signal success and |error_callback|
   // for failures. This method only applies to remote characteristics and will
   // fail for those that are locally hosted.
   virtual void WriteRemoteCharacteristic(
       int offset,
       const std::vector<uint8>& new_value,
       const base::Closure& callback,
       const ErrorCallback& error_callback) = 0;
 
  protected:
   BluetoothGattCharacteristic();
   virtual ~BluetoothGattCharacteristic();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BluetoothGattCharacteristic);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_BLUETOOTH_GATT_CHARACTERISTIC_H_