#pragma once
#include <type_traits>
#include <utility>
#include <wtf/RefCounted.h>
namespace WTF {
template<typename T> class NeverDestroyed {
WTF_MAKE_NONCOPYABLE(NeverDestroyed);
public:
template<typename... Args> NeverDestroyed(Args&&... args)
{
MaybeRelax<T>(new (storagePointer()) T(std::forward<Args>(args)...));
}
NeverDestroyed(NeverDestroyed&& other)
{
MaybeRelax<T>(new (storagePointer()) T(WTFMove(other)));
}
operator T&() { return *storagePointer(); }
T& get() { return *storagePointer(); }
operator const T&() const { return *storagePointer(); }
const T& get() const { return *storagePointer(); }
private:
using PointerType = typename std::remove_const<T>::type*;
PointerType storagePointer() const { return const_cast<PointerType>(reinterpret_cast<const T*>(&m_storage)); }
typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_storage;
template<typename PtrType, bool ShouldRelax = std::is_base_of<RefCountedBase, PtrType>::value> struct MaybeRelax {
explicit MaybeRelax(PtrType*) { }
};
template<typename PtrType> struct MaybeRelax<PtrType, true> {
explicit MaybeRelax(PtrType* ptr) { ptr->relaxAdoptionRequirement(); }
};
};
template<typename T> NeverDestroyed<T> makeNeverDestroyed(T&&);
template<typename T> class LazyNeverDestroyed {
WTF_MAKE_NONCOPYABLE(LazyNeverDestroyed);
public:
LazyNeverDestroyed() = default;
template<typename... Args>
void construct(Args&&... args)
{
ASSERT(!m_isConstructed);
#if !ASSERT_DISABLED
m_isConstructed = true;
#endif
MaybeRelax<T>(new (storagePointer()) T(std::forward<Args>(args)...));
}
operator T&() { return *storagePointer(); }
T& get() { return *storagePointer(); }
T* operator->() { return storagePointer(); }
operator const T&() const { return *storagePointer(); }
const T& get() const { return *storagePointer(); }
const T* operator->() const { return storagePointer(); }
#if !ASSERT_DISABLED
bool isConstructed() const { return m_isConstructed; }
#endif
private:
using PointerType = typename std::remove_const<T>::type*;
PointerType storagePointer() const
{
ASSERT(m_isConstructed);
return const_cast<PointerType>(reinterpret_cast<const T*>(&m_storage));
}
typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type m_storage;
template<typename PtrType, bool ShouldRelax = std::is_base_of<RefCountedBase, PtrType>::value> struct MaybeRelax {
explicit MaybeRelax(PtrType*) { }
};
template<typename PtrType> struct MaybeRelax<PtrType, true> {
explicit MaybeRelax(PtrType* ptr) { ptr->relaxAdoptionRequirement(); }
};
#if !ASSERT_DISABLED
bool m_isConstructed;
#endif
};
template<typename T> inline NeverDestroyed<T> makeNeverDestroyed(T&& argument)
{
return WTFMove(argument);
}
}
using WTF::LazyNeverDestroyed;
using WTF::NeverDestroyed;
using WTF::makeNeverDestroyed;