Implement WebBluetooth getDescriptor[s]

third_party/WebKit/Source/modules/bluetooth/BluetoothAttributeInstanceMap.cpp

 // Copyright 2016 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.
 
 #include "modules/bluetooth/BluetoothAttributeInstanceMap.h"
 
 #include "modules/bluetooth/BluetoothDevice.h"
 #include "modules/bluetooth/BluetoothRemoteGATTService.h"
 #include <memory>
 #include <utility>
@@ skipping 44 matching lines @@
   }
 
   return characteristic;
 }
 
 bool BluetoothAttributeInstanceMap::containsCharacteristic(
     const String& characteristicInstanceId) {
   return m_characteristicIdToObject.contains(characteristicInstanceId);
 }
 
+BluetoothRemoteGATTDescriptor*
+BluetoothAttributeInstanceMap::getOrCreateBluetoothRemoteGATTDescriptor(
+    mojom::blink::WebBluetoothRemoteGATTDescriptorPtr descriptor,
+    BluetoothRemoteGATTCharacteristic* characteristic) {
+  String instanceId = descriptor->instance_id;

[dcheng, 2017/01/13 22:48:33]

nit: const String& so it's just a cheap alias?

(String is already cheap to copy, but it's even cheaper if we don't copy at all)

[dougt, 2017/01/14 02:34:20]

That goes boom.

|descriptor| is std::moved into an object |result| that is stored in the
m_descriptorIdToObject map. After the move, |descriptor| is in a valid
but unspecified state.  So, we must not use it.

This is a modified version of getOrCreateRemoteGATTCharacteristic:

const String& instanceId =
  remoteGATTCharacteristic->instance_id;  <--- ref to member of moved-from
BluetoothRemoteGATTCharacteristic* characteristic =
    m_characteristicIdToObject.get(instanceId);
if (!characteristic) {
  characteristic = BluetoothRemoteGATTCharacteristic::create(
      context,
      std::move(remoteGATTCharacteristic), <-- move
      service, m_device);
  m_characteristicIdToObject.add(instanceId,   <-- usage
                                 characteristic);
}

+  BluetoothRemoteGATTDescriptor* result =
+      m_descriptorIdToObject.get(instanceId);
+
+  if (result)
+    return result;
+
+  result =
+      new BluetoothRemoteGATTDescriptor(std::move(descriptor), characteristic);
+  m_descriptorIdToObject.add(instanceId, result);
+  return result;
+}
+
+bool BluetoothAttributeInstanceMap::containsDescriptor(
+    const String& descriptorInstanceId) {
+  return m_descriptorIdToObject.contains(descriptorInstanceId);
+}
+
 void BluetoothAttributeInstanceMap::Clear() {
   m_serviceIdToObject.clear();
   m_characteristicIdToObject.clear();
+  m_descriptorIdToObject.clear();
 }
 
 DEFINE_TRACE(BluetoothAttributeInstanceMap) {
   visitor->trace(m_device);
   visitor->trace(m_serviceIdToObject);
   visitor->trace(m_characteristicIdToObject);
+  visitor->trace(m_descriptorIdToObject);
 }
 
 }  // namespace blink