#ifndef NeverDestroyed_h
#define NeverDestroyed_h
#include <type_traits>
#include <utility>
#include <wtf/Noncopyable.h>
#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 (asPtr()) T(std::forward<Args>(args)...));
}
operator T&() { return *asPtr(); }
T& get() { return *asPtr(); }
private:
typedef typename std::remove_const<T>::type* PointerType;
PointerType asPtr() { return reinterpret_cast<PointerType>(&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<RefCounted<PtrType>, PtrType>::value> struct MaybeRelax {
explicit MaybeRelax(PtrType*) { }
};
template <typename PtrType> struct MaybeRelax<PtrType, true> {
explicit MaybeRelax(PtrType* ptr) { ptr->relaxAdoptionRequirement(); }
};
};
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 (asPtr()) T(std::forward<Args>(args)...));
}
operator T&() { return *asPtr(); }
T& get() { return *asPtr(); }
private:
typedef typename std::remove_const<T>::type* PointerType;
PointerType asPtr()
{
ASSERT(m_isConstructed);
return reinterpret_cast<PointerType>(&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<RefCounted<PtrType>, 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 = false;
#endif
};
}
using WTF::LazyNeverDestroyed;
using WTF::NeverDestroyed;
#endif // NeverDestroyed_h