bsnes-libretro/nall/maybe.hpp
Tim Allen f9adb4d2c6 Update to v106r58 release.
byuu says:

The main thing I worked on today was emulating the MBC7 EEPROM.

And... I have many things to say about that, but not here, and not now...

The missing EEPROM support is why the accelerometer was broken. Although
it's not evidently clear that I'm emulating the actual values
incorrectly. I'll think about it and get it fixed, though.

bsnes went from ~308fps to ~328fps, and I don't even know why. Probably
something somewhere in the 140KB of changes to other things made in this
WIP.
2018-08-21 13:17:12 +10:00

92 lines
3.4 KiB
C++

#pragma once
namespace nall {
struct nothing_t {};
static nothing_t nothing;
struct else_t {};
template<typename T>
struct maybe {
inline maybe() {}
inline maybe(nothing_t) {}
inline maybe(const T& source) { operator=(source); }
inline maybe(T&& source) { operator=(move(source)); }
inline maybe(const maybe& source) { operator=(source); }
inline maybe(maybe&& source) { operator=(move(source)); }
inline ~maybe() { reset(); }
inline auto operator=(nothing_t) -> maybe& { reset(); return *this; }
inline auto operator=(const T& source) -> maybe& { reset(); _valid = true; new(&_value.t) T(source); return *this; }
inline auto operator=(T&& source) -> maybe& { reset(); _valid = true; new(&_value.t) T(move(source)); return *this; }
inline auto operator=(const maybe& source) -> maybe& {
if(this == &source) return *this;
reset();
if(_valid = source._valid) new(&_value.t) T(source.get());
return *this;
}
inline auto operator=(maybe&& source) -> maybe& {
if(this == &source) return *this;
reset();
if(_valid = source._valid) new(&_value.t) T(move(source.get()));
return *this;
}
inline explicit operator bool() const { return _valid; }
inline auto reset() -> void { if(_valid) { _value.t.~T(); _valid = false; } }
inline auto data() -> T* { return _valid ? &_value.t : nullptr; }
inline auto get() -> T& { assert(_valid); return _value.t; }
inline auto data() const -> const T* { return ((maybe*)this)->data(); }
inline auto get() const -> const T& { return ((maybe*)this)->get(); }
inline auto operator->() -> T* { return data(); }
inline auto operator->() const -> const T* { return data(); }
inline auto operator*() -> T& { return get(); }
inline auto operator*() const -> const T& { return get(); }
inline auto operator()() -> T& { return get(); }
inline auto operator()() const -> const T& { return get(); }
inline auto operator()(const T& invalid) const -> const T& { return _valid ? get() : invalid; }
private:
union U {
T t;
U() {}
~U() {}
} _value;
bool _valid = false;
};
template<typename T>
struct maybe<T&> {
inline maybe() : _value(nullptr) {}
inline maybe(nothing_t) : _value(nullptr) {}
inline maybe(const T& source) : _value((T*)&source) {}
inline maybe(const maybe& source) : _value(source._value) {}
inline auto operator=(nothing_t) -> maybe& { _value = nullptr; return *this; }
inline auto operator=(const T& source) -> maybe& { _value = (T*)&source; return *this; }
inline auto operator=(const maybe& source) -> maybe& { _value = source._value; return *this; }
inline explicit operator bool() const { return _value; }
inline auto reset() -> void { _value = nullptr; }
inline auto data() -> T* { return _value; }
inline auto get() -> T& { assert(_value); return *_value; }
inline auto data() const -> const T* { return ((maybe*)this)->data(); }
inline auto get() const -> const T& { return ((maybe*)this)->get(); }
inline auto operator->() -> T* { return data(); }
inline auto operator->() const -> const T* { return data(); }
inline auto operator*() -> T& { return get(); }
inline auto operator*() const -> const T& { return get(); }
inline auto operator()() -> T& { return get(); }
inline auto operator()() const -> const T& { return get(); }
inline auto operator()(const T& invalid) const -> const T& { return _value ? get() : invalid; }
private:
T* _value;
};
}