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#pragma once
#include <util/system/atexit.h>
#include <util/system/compiler.h>
#include <atomic>
#include <new>
#include <utility>
template <class T>
struct TSingletonTraits {
static constexpr size_t Priority = 65536;
};
namespace NPrivate {
void FillWithTrash(void* ptr, size_t len);
void LockRecursive(std::atomic<size_t>& lock) noexcept;
void UnlockRecursive(std::atomic<size_t>& lock) noexcept;
template <class T>
void Destroyer(void* ptr) {
((T*)ptr)->~T();
FillWithTrash(ptr, sizeof(T));
}
template <class T, size_t P, class... TArgs>
Y_NO_INLINE T* SingletonBase(std::atomic<T*>& ptr, TArgs&&... args) {
alignas(T) static char buf[sizeof(T)];
static std::atomic<size_t> lock;
LockRecursive(lock);
auto ret = ptr.load();
try {
if (!ret) {
ret = ::new (buf) T(std::forward<TArgs>(args)...);
try {
AtExit(Destroyer<T>, ret, P);
} catch (...) {
Destroyer<T>(ret);
throw;
}
ptr.store(ret);
}
} catch (...) {
UnlockRecursive(lock);
throw;
}
UnlockRecursive(lock);
return ret;
}
template <class T, size_t P, class... TArgs>
T* SingletonInt(TArgs&&... args) {
static_assert(sizeof(T) < 32000, "use HugeSingleton instead");
static std::atomic<T*> ptr;
auto ret = ptr.load();
if (Y_UNLIKELY(!ret)) {
ret = SingletonBase<T, P>(ptr, std::forward<TArgs>(args)...);
}
return ret;
}
template <class T>
class TDefault {
public:
template <class... TArgs>
inline TDefault(TArgs&&... args)
: T_(std::forward<TArgs>(args)...)
{
}
inline const T* Get() const noexcept {
return &T_;
}
private:
T T_;
};
template <class T>
struct THeapStore {
template <class... TArgs>
inline THeapStore(TArgs&&... args)
: D(new T(std::forward<TArgs>(args)...))
{
}
inline ~THeapStore() {
delete D;
}
T* D;
};
} // namespace NPrivate
#define Y_DECLARE_SINGLETON_FRIEND() \
template <class T, size_t P, class... TArgs> \
friend T* ::NPrivate::SingletonInt(TArgs&&...); \
template <class T, size_t P, class... TArgs> \
friend T* ::NPrivate::SingletonBase(std::atomic<T*>&, TArgs&&...);
template <class T, class... TArgs>
Y_RETURNS_NONNULL T* Singleton(TArgs&&... args) {
return ::NPrivate::SingletonInt<T, TSingletonTraits<T>::Priority>(std::forward<TArgs>(args)...);
}
template <class T, class... TArgs>
Y_RETURNS_NONNULL T* HugeSingleton(TArgs&&... args) {
return Singleton<::NPrivate::THeapStore<T>>(std::forward<TArgs>(args)...)->D;
}
template <class T, size_t P, class... TArgs>
Y_RETURNS_NONNULL T* SingletonWithPriority(TArgs&&... args) {
return ::NPrivate::SingletonInt<T, P>(std::forward<TArgs>(args)...);
}
template <class T, size_t P, class... TArgs>
Y_RETURNS_NONNULL T* HugeSingletonWithPriority(TArgs&&... args) {
return SingletonWithPriority<::NPrivate::THeapStore<T>, P>(std::forward<TArgs>(args)...)->D;
}
template <class T>
const T& Default() {
return *(::NPrivate::SingletonInt<typename ::NPrivate::TDefault<T>, TSingletonTraits<T>::Priority>()->Get());
}
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