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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,
std::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_v<std::remove_cv_t<T>>;
static void Finalize(void* obj) {
internal::FinalizerTraitImpl<T, kNonTrivialFinalizer>::Finalize(obj);
}
public:
static constexpr bool HasFinalizer() { return kNonTrivialFinalizer; }
// 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_
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