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

//
// Copyright 2020 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_DUAL_REF_COUNTED_H
#define GRPC_SRC_CORE_LIB_GPRPP_DUAL_REF_COUNTED_H

#include <grpc/support/port_platform.h>

#include <atomic>
#include <cstdint>

#include <grpc/support/log.h>

#include "src/core/lib/gprpp/debug_location.h"
#include "src/core/lib/gprpp/orphanable.h"
#include "src/core/lib/gprpp/ref_counted_ptr.h"

namespace grpc_core {

// DualRefCounted is an interface for reference-counted objects with two
// classes of refs: strong refs (usually just called "refs") and weak refs.
// This supports cases where an object needs to start shutting down when
// all external callers are done with it (represented by strong refs) but
// cannot be destroyed until all internal callbacks are complete
// (represented by weak refs).
//
// Each class of refs can be incremented and decremented independently.
// Objects start with 1 strong ref and 0 weak refs at instantiation.
// When the strong refcount reaches 0, the object's Orphan() method is called.
// When the weak refcount reaches 0, the object is destroyed.
//
// This will be used by CRTP (curiously-recurring template pattern), e.g.:
//   class MyClass : public RefCounted<MyClass> { ... };
template <typename Child>
class DualRefCounted : public Orphanable { … };

}  // namespace grpc_core

#endif  // GRPC_SRC_CORE_LIB_GPRPP_DUAL_REF_COUNTED_H