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#pragma once
#include <util/generic/ptr.h>
#include <util/generic/vector.h>
#include <array>
#include <functional>
#include <mutex>
namespace NThreading {
class IGenericLocalStorage {
public:
struct TTraits {
size_t Size = 0;
std::function<void(void*)> Constructor;
std::function<void(void*)> Destructor;
};
struct TData
: TNonCopyable
{
TVector<char> Memory;
std::function<void(void*)> Destructor;
public:
~TData() {
if (Destructor) {
Destructor(&Memory[0]);
}
}
};
public:
virtual ~IGenericLocalStorage() {};
void* GetMemory(const TTraits& traits) const {
TData* data = GetData();
if (!data->Destructor) {
data->Destructor = traits.Destructor;
data->Memory.resize(traits.Size);
traits.Constructor(&data->Memory[0]);
}
return &data->Memory[0];
}
private:
virtual TData* GetData() const = 0;
};
class IGLSContext {
public:
virtual ~IGLSContext() = default;
virtual bool IsCurrent() const = 0;
virtual THolder<IGenericLocalStorage> MakeStorage() const = 0;
};
// Later registrations take priority over earlier ones.
void RegisterGLSContext(THolder<IGLSContext> context);
namespace NDetail {
inline constexpr size_t MaxGLSContexts = 4;
size_t GLSContextCount();
const IGLSContext& GetGLSContext(size_t index);
}
template <typename T>
class TGenericLocalValue {
private:
struct TSlot {
std::once_flag InitOnce;
THolder<IGenericLocalStorage> Storage;
};
static const auto& Traits() {
const static IGenericLocalStorage::TTraits traits = {
.Size = sizeof(T),
.Constructor = [](void* addr) { new (addr) T(); },
.Destructor = [](void* addr) { static_cast<T*>(addr)->~T(); }
};
return traits;
};
public:
T* Get() const {
const size_t count = NDetail::GLSContextCount();
for (size_t index = count; index-- > 0;) {
const IGLSContext& context = NDetail::GetGLSContext(index);
if (context.IsCurrent()) {
return GetMemory(ContextSlots_[index], context);
}
}
Y_ABORT("unreachable, ContextSlots_[0] always IsCurrent");
}
T& GetRef() const {
return *Get();
}
private:
T* GetMemory(TSlot& slot, const IGLSContext& context) const {
std::call_once(slot.InitOnce, [&] { slot.Storage = context.MakeStorage(); });
return static_cast<T*>(slot.Storage->GetMemory(Traits()));
}
private:
mutable std::array<TSlot, NDetail::MaxGLSContexts> ContextSlots_;
};
}
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