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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
#include <AK/kmalloc.h>
namespace AK {
template<typename T>
class alignas(T) [[nodiscard]] Optional {
public:
using ValueType = T;
ALWAYS_INLINE Optional() = default;
ALWAYS_INLINE Optional(const T& value)
: m_has_value(true)
{
new (&m_storage) T(value);
}
template<typename U>
ALWAYS_INLINE Optional(const U& value)
: m_has_value(true)
{
new (&m_storage) T(value);
}
ALWAYS_INLINE Optional(T&& value)
: m_has_value(true)
{
new (&m_storage) T(move(value));
}
ALWAYS_INLINE Optional(Optional&& other)
: m_has_value(other.m_has_value)
{
if (other.has_value()) {
new (&m_storage) T(other.release_value());
other.m_has_value = false;
}
}
ALWAYS_INLINE Optional(const Optional& other)
: m_has_value(other.m_has_value)
{
if (m_has_value) {
new (&m_storage) T(other.value());
}
}
ALWAYS_INLINE Optional& operator=(const Optional& other)
{
if (this != &other) {
clear();
m_has_value = other.m_has_value;
if (m_has_value) {
new (&m_storage) T(other.value());
}
}
return *this;
}
ALWAYS_INLINE Optional& operator=(Optional&& other)
{
if (this != &other) {
clear();
m_has_value = other.m_has_value;
if (other.has_value())
new (&m_storage) T(other.release_value());
}
return *this;
}
template<typename O>
ALWAYS_INLINE bool operator==(const Optional<O>& other) const
{
return has_value() == other.has_value() && (!has_value() || value() == other.value());
}
ALWAYS_INLINE ~Optional()
{
clear();
}
ALWAYS_INLINE void clear()
{
if (m_has_value) {
value().~T();
m_has_value = false;
}
}
template<typename... Parameters>
ALWAYS_INLINE void emplace(Parameters&&... parameters)
{
clear();
m_has_value = true;
new (&m_storage) T(forward<Parameters>(parameters)...);
}
[[nodiscard]] ALWAYS_INLINE bool has_value() const { return m_has_value; }
[[nodiscard]] ALWAYS_INLINE T& value()
{
VERIFY(m_has_value);
return *reinterpret_cast<T*>(&m_storage);
}
[[nodiscard]] ALWAYS_INLINE const T& value() const
{
VERIFY(m_has_value);
return *reinterpret_cast<const T*>(&m_storage);
}
[[nodiscard]] T release_value()
{
VERIFY(m_has_value);
T released_value = move(value());
value().~T();
m_has_value = false;
return released_value;
}
[[nodiscard]] ALWAYS_INLINE T value_or(const T& fallback) const
{
if (m_has_value)
return value();
return fallback;
}
ALWAYS_INLINE const T& operator*() const { return value(); }
ALWAYS_INLINE T& operator*() { return value(); }
ALWAYS_INLINE const T* operator->() const { return &value(); }
ALWAYS_INLINE T* operator->() { return &value(); }
private:
u8 m_storage[sizeof(T)] { 0 };
bool m_has_value { false };
};
}
using AK::Optional;
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