chromium/third_party/grpc/src/src/core/lib/gprpp/single_set_ptr.h

// Copyright 2022 gRPC authors.
//
// 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 GRPC_SRC_CORE_LIB_GPRPP_SINGLE_SET_PTR_H
#define GRPC_SRC_CORE_LIB_GPRPP_SINGLE_SET_PTR_H

#include <grpc/support/port_platform.h>

#include <atomic>
#include <memory>

#include <grpc/support/log.h>

namespace grpc_core {

template <class T, class Deleter = std::default_delete<T>>
class SingleSetPtr {
 public:
  SingleSetPtr() = default;
  explicit SingleSetPtr(T* p) : … { … }
  explicit SingleSetPtr(std::unique_ptr<T, Deleter> p) : … { … }
  ~SingleSetPtr() { … }

  SingleSetPtr(const SingleSetPtr&) = delete;
  SingleSetPtr& operator=(const SingleSetPtr&) = delete;
  SingleSetPtr(SingleSetPtr&& other) noexcept
      : … { … }
  SingleSetPtr& operator=(SingleSetPtr&& other) noexcept { … }

  // Set the pointer;
  // if already set, return the pre-set value and delete ptr;
  // if deleted, return nullptr and delete ptr.
  T* Set(T* ptr) { … }

  // Set the pointer from a compatible unique_ptr - with the same caveats as
  // above.
  T* Set(std::unique_ptr<T, Deleter> ptr) { … }

  // Clear the pointer.
  void Reset() { … }

  bool is_set() const { … }

  T* operator->() const { … }

  T& operator*() const { … }

 private:
  static void Delete(T* p) { … }
  std::atomic<T*> p_{nullptr};
};

}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_GPRPP_SINGLE_SET_PTR_H