macros.h

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/******************************************************************************
 * Copyright 2018 The Apollo Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *****************************************************************************/

#ifndef CYBER_COMMON_MACROS_H_
#define CYBER_COMMON_MACROS_H_

#include <iostream>
#include <memory>
#include <mutex>
#include <type_traits>
#include <utility>

#include "cyber/base/macros.h"

DEFINE_TYPE_TRAIT(HasShutdown, Shutdown)

template <typename T>
typename std::enable_if<HasShutdown<T>::value>::type CallShutdown(T *instance) {
  instance->Shutdown();
}

template <typename T>
typename std::enable_if<!HasShutdown<T>::value>::type CallShutdown(
    T *instance) {
  (void)instance;
}

// There must be many copy-paste versions of these macros which are same
// things, undefine them to avoid conflict.
#undef UNUSED
#undef DISALLOW_COPY_AND_ASSIGN

#define UNUSED(param) (void)param

#define DISALLOW_COPY_AND_ASSIGN(classname) \
  classname(const classname &) = delete;    \
  classname &operator=(const classname &) = delete;

#define DECLARE_SINGLETON(classname)                                      \
 public:                                                                  \
  static classname *Instance(bool create_if_needed = true) {              \
    static classname *instance = nullptr;                                 \
    if (!instance && create_if_needed) {                                  \
      static std::once_flag flag;                                         \
      std::call_once(flag,                                                \
                     [&] { instance = new (std::nothrow) classname(); }); \
    }                                                                     \
    return instance;                                                      \
  }                                                                       \
                                                                          \
  static void CleanUp() {                                                 \
    auto instance = Instance(false);                                      \
    if (instance != nullptr) {                                            \
      CallShutdown(instance);                                             \
    }                                                                     \
  }                                                                       \
                                                                          \
 private:                                                                 \
  classname();                                                            \
  DISALLOW_COPY_AND_ASSIGN(classname)

#endif  // CYBER_COMMON_MACROS_H_