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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Daniel Bertalan <dani@danielbertalan.dev>
*
* 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 {
// NOTE: If you're here because of an internal compiler error in GCC 10.3.0+,
// it's because of the following bug:
//
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96745
//
// Make sure you didn't accidentally make your destructor private before
// you start bug hunting. :^)
template<typename T>
class [[nodiscard]] Optional {
public:
using ValueType = T;
ALWAYS_INLINE Optional() = default;
#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
Optional(Optional const& other) requires(!IsCopyConstructible<T>) = delete;
Optional(Optional const& other) = default;
Optional(Optional&& other) requires(!IsMoveConstructible<T>) = delete;
Optional& operator=(Optional const&) requires(!IsCopyConstructible<T> || !IsDestructible<T>) = delete;
Optional& operator=(Optional const&) = default;
Optional& operator=(Optional&& other) requires(!IsMoveConstructible<T> || !IsDestructible<T>) = delete;
~Optional() requires(!IsDestructible<T>) = delete;
~Optional() = default;
#endif
ALWAYS_INLINE Optional(Optional const& other)
#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
requires(!IsTriviallyCopyConstructible<T>)
#endif
: m_has_value(other.m_has_value)
{
if (other.has_value()) {
new (&m_storage) T(other.value());
}
}
ALWAYS_INLINE Optional(Optional&& other)
: m_has_value(other.m_has_value)
{
if (other.has_value()) {
new (&m_storage) T(other.release_value());
}
}
template<typename U = T>
ALWAYS_INLINE explicit(!IsConvertible<U&&, T>) Optional(U&& value) requires(!IsSame<RemoveCVReference<U>, Optional<T>> && IsConstructible<T, U&&>)
: m_has_value(true)
{
new (&m_storage) T(forward<U>(value));
}
ALWAYS_INLINE Optional& operator=(Optional const& other)
#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
requires(!IsTriviallyCopyConstructible<T> || !IsTriviallyDestructible<T>)
#endif
{
if (this != &other) {
clear();
m_has_value = other.m_has_value;
if (other.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==(Optional<O> const& other) const
{
return has_value() == other.has_value() && (!has_value() || value() == other.value());
}
template<typename O>
ALWAYS_INLINE bool operator==(O const& other) const
{
return has_value() && value() == other;
}
ALWAYS_INLINE ~Optional()
#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
requires(!IsTriviallyDestructible<T>)
#endif
{
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 *__builtin_launder(reinterpret_cast<T*>(&m_storage));
}
[[nodiscard]] ALWAYS_INLINE T const& value() const&
{
VERIFY(m_has_value);
return *__builtin_launder(reinterpret_cast<T const*>(&m_storage));
}
[[nodiscard]] ALWAYS_INLINE T value() &&
{
return release_value();
}
[[nodiscard]] ALWAYS_INLINE 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(T const& fallback) const&
{
if (m_has_value)
return value();
return fallback;
}
[[nodiscard]] ALWAYS_INLINE T value_or(T&& fallback) &&
{
if (m_has_value)
return move(value());
return move(fallback);
}
ALWAYS_INLINE T const& operator*() const { return value(); }
ALWAYS_INLINE T& operator*() { return value(); }
ALWAYS_INLINE T const* operator->() const { return &value(); }
ALWAYS_INLINE T* operator->() { return &value(); }
private:
alignas(T) u8 m_storage[sizeof(T)];
bool m_has_value { false };
};
}
using AK::Optional;
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