orphanable.h

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/*
 *
 * Copyright 2017 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_CORE_LIB_GPRPP_ORPHANABLE_H
#define GRPC_CORE_LIB_GPRPP_ORPHANABLE_H
 
#include <grpc/support/port_platform.h>
 
#include <cinttypes>
#include <memory>
#include <utility>
 
#include "src/core/lib/gprpp/debug_location.h"
#include "src/core/lib/gprpp/ref_counted.h"
#include "src/core/lib/gprpp/ref_counted_ptr.h"
 
namespace grpc_core {
 
// A base class for orphanable objects, which have one external owner
// but are not necessarily destroyed immediately when the external owner
// gives up ownership.  Instead, the owner calls the object's Orphan()
// method, and the object then takes responsibility for its own cleanup
// and destruction.
class Orphanable {
 public:
  // Gives up ownership of the object.  The implementation must arrange
  // to eventually destroy the object without further interaction from the
  // caller.
  virtual void Orphan() = 0;
 
  // Not copyable or movable.
  Orphanable(const Orphanable&) = delete;
  Orphanable& operator=(const Orphanable&) = delete;
 
 protected:
  Orphanable() {}
  virtual ~Orphanable() {}
};
 
class OrphanableDelete {
 public:
  template <typename T>
  void operator()(T* p) {
    p->Orphan();
  }
};
 
template <typename T, typename Deleter = OrphanableDelete>
using OrphanablePtr = std::unique_ptr<T, Deleter>;
 
template <typename T, typename... Args>
inline OrphanablePtr<T> MakeOrphanable(Args&&... args) {
  return OrphanablePtr<T>(new T(std::forward<Args>(args)...));
}
 
// A type of Orphanable with internal ref-counting.
template <typename Child, UnrefBehavior UnrefBehaviorArg = kUnrefDelete>
class InternallyRefCounted : public Orphanable {
 public:
  // Not copyable nor movable.
  InternallyRefCounted(const InternallyRefCounted&) = delete;
  InternallyRefCounted& operator=(const InternallyRefCounted&) = delete;
 
 protected:
  // Allow RefCountedPtr<> to access Unref() and IncrementRefCount().
  template <typename T>
  friend class RefCountedPtr;
 
  // Note: Tracing is a no-op on non-debug builds.
  explicit InternallyRefCounted(const char* trace = nullptr,
                                intptr_t initial_refcount = 1)
      : refs_(initial_refcount, trace) {}
  ~InternallyRefCounted() override = default;
 
  RefCountedPtr<Child> Ref() GRPC_MUST_USE_RESULT {
    IncrementRefCount();
    return RefCountedPtr<Child>(static_cast<Child*>(this));
  }
  RefCountedPtr<Child> Ref(const DebugLocation& location,
                           const char* reason) GRPC_MUST_USE_RESULT {
    IncrementRefCount(location, reason);
    return RefCountedPtr<Child>(static_cast<Child*>(this));
  }
 
  void Unref() {
    if (GPR_UNLIKELY(refs_.Unref())) {
      internal::Delete<Child, UnrefBehaviorArg>(static_cast<Child*>(this));
    }
  }
  void Unref(const DebugLocation& location, const char* reason) {
    if (GPR_UNLIKELY(refs_.Unref(location, reason))) {
      internal::Delete<Child, UnrefBehaviorArg>(static_cast<Child*>(this));
    }
  }
 
 private:
  void IncrementRefCount() { refs_.Ref(); }
  void IncrementRefCount(const DebugLocation& location, const char* reason) {
    refs_.Ref(location, reason);
  }
 
  RefCount refs_;
};
 
}  // namespace grpc_core
 
#endif /* GRPC_CORE_LIB_GPRPP_ORPHANABLE_H */