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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_
#define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_

#include <type_traits>

#include "cppgc/type-traits.h"

namespace cppgc {
namespace internal {

using FinalizationCallback = void (*)(void*);

template <typename T, typename = void>
struct HasFinalizeGarbageCollectedObject : std::false_type {};

template <typename T>
struct HasFinalizeGarbageCollectedObject<
    T, void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>>
    : std::true_type {};

// The FinalizerTraitImpl specifies how to finalize objects.
template <typename T, bool isFinalized>
struct FinalizerTraitImpl;

template <typename T>
struct FinalizerTraitImpl<T, true> {
 private:
  // Dispatch to custom FinalizeGarbageCollectedObject().
  struct Custom {
    static void Call(void* obj) {
      static_cast<T*>(obj)->FinalizeGarbageCollectedObject();
    }
  };

  // Dispatch to regular destructor.
  struct Destructor {
    static void Call(void* obj) { static_cast<T*>(obj)->~T(); }
  };

  using FinalizeImpl =
      std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom,
                         Destructor>;

 public:
  static void Finalize(void* obj) {
    static_assert(sizeof(T), "T must be fully defined");
    FinalizeImpl::Call(obj);
  }
};

template <typename T>
struct FinalizerTraitImpl<T, false> {
  static void Finalize(void* obj) {
    static_assert(sizeof(T), "T must be fully defined");
  }
};

// The FinalizerTrait is used to determine if a type requires finalization and
// what finalization means.
template <typename T>
struct FinalizerTrait {
 private:
  // Object has a finalizer if it has
  // - a custom FinalizeGarbageCollectedObject method, or
  // - a destructor.
  static constexpr bool kNonTrivialFinalizer =
      internal::HasFinalizeGarbageCollectedObject<T>::value ||
      !std::is_trivially_destructible<typename std::remove_cv<T>::type>::value;

  static void Finalize(void* obj) {
    internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj);
  }

 public:
  // The callback used to finalize an object of type T.
  static constexpr FinalizationCallback kCallback =
      kNonTrivialFinalizer ? Finalize : nullptr;
};

template <typename T>
constexpr FinalizationCallback FinalizerTrait<T>::kCallback;

}  // namespace internal
}  // namespace cppgc

#endif  // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_

	// Copyright 2020 the V8 project authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#ifndef INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_
	#define INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_

	#include <type_traits>

	#include "cppgc/type-traits.h"

	namespace cppgc {
	namespace internal {

	using FinalizationCallback = void ()(void);

	template <typename T, typename = void>
	struct HasFinalizeGarbageCollectedObject : std::false_type {};

	template <typename T>
	struct HasFinalizeGarbageCollectedObject<
	T, void_t<decltype(std::declval<T>().FinalizeGarbageCollectedObject())>>
	: std::true_type {};

	// The FinalizerTraitImpl specifies how to finalize objects.
	template <typename T, bool isFinalized>
	struct FinalizerTraitImpl;

	template <typename T>
	struct FinalizerTraitImpl<T, true> {
	private:
	// Dispatch to custom FinalizeGarbageCollectedObject().
	struct Custom {
	static void Call(void* obj) {
	static_cast<T*>(obj)->FinalizeGarbageCollectedObject();
	}
	};

	// Dispatch to regular destructor.
	struct Destructor {
	static void Call(void* obj) { static_cast<T*>(obj)->~T(); }
	};

	using FinalizeImpl =
	std::conditional_t<HasFinalizeGarbageCollectedObject<T>::value, Custom,
	Destructor>;

	public:
	static void Finalize(void* obj) {
	static_assert(sizeof(T), "T must be fully defined");
	FinalizeImpl::Call(obj);
	}
	};

	template <typename T>
	struct FinalizerTraitImpl<T, false> {
	static void Finalize(void* obj) {
	static_assert(sizeof(T), "T must be fully defined");
	}
	};

	// The FinalizerTrait is used to determine if a type requires finalization and
	// what finalization means.
	template <typename T>
	struct FinalizerTrait {
	private:
	// Object has a finalizer if it has
	// - a custom FinalizeGarbageCollectedObject method, or
	// - a destructor.
	static constexpr bool kNonTrivialFinalizer =
	internal::HasFinalizeGarbageCollectedObject<T>::value \|\|
	!std::is_trivially_destructible<typename std::remove_cv<T>::type>::value;

	static void Finalize(void* obj) {
	internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj);
	}

	public:
	// The callback used to finalize an object of type T.
	static constexpr FinalizationCallback kCallback =
	kNonTrivialFinalizer ? Finalize : nullptr;
	};

	template <typename T>
	constexpr FinalizationCallback FinalizerTrait<T>::kCallback;

	} // namespace internal
	} // namespace cppgc

	#endif // INCLUDE_CPPGC_INTERNAL_FINALIZER_TRAIT_H_