1 /*
2  * Copyright (C) 2021 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 #pragma once
17 
18 #include <android-base/logging.h>
19 #include <android/binder_interface_utils.h>
20 #include <utils/Mutex.h>
21 
22 namespace android::hardware::radio::compat {
23 
24 template <typename Interface, typename DefaultImplementation, bool isIndication = false>
25 class GuaranteedCallback {
26     mutable std::mutex mCallbackGuard;
27     std::shared_ptr<Interface> mCallback GUARDED_BY(mCallbackGuard);
28 
29   public:
30     GuaranteedCallback<Interface, DefaultImplementation, isIndication>& operator=(
31             const std::shared_ptr<Interface>& callback) {
32         CHECK(callback);
33         const std::lock_guard<std::mutex> lock(mCallbackGuard);
34         mCallback = callback;
35         return *this;
36     }
37 
get()38     std::shared_ptr<Interface> get() {
39         if (mCallback) return mCallback;
40         const std::lock_guard<std::mutex> lock(mCallbackGuard);
41         if (mCallback) return mCallback;
42 
43         LOG(isIndication ? WARNING : ERROR) << "Callback is not set";
44         return mCallback = ndk::SharedRefBase::make<DefaultImplementation>();
45     }
46 
47     operator bool() const { return mCallback != nullptr; }
48 };
49 
50 }  // namespace android::hardware::radio::compat
51