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#pragma once
#include <AK/Assertions.h>
#include <AK/Platform.h>
template<typename T>
class CONSUMABLE(unknown) alignas(T) Optional {
public:
RETURN_TYPESTATE(unknown)
Optional() {}
RETURN_TYPESTATE(unknown)
Optional(T&& value)
: m_has_value(true)
{
new (&m_storage) T(move(value));
}
template<typename U>
RETURN_TYPESTATE(unknown)
Optional(U&& value)
: m_has_value(true)
{
new (&m_storage) T(move(value));
}
RETURN_TYPESTATE(unknown)
Optional(Optional&& other)
: m_has_value(other.m_has_value)
{
if (m_has_value) {
new (&m_storage) T(move(other.value_without_consume_state()));
other.m_has_value = false;
}
}
RETURN_TYPESTATE(unknown)
Optional(const Optional& other)
: m_has_value(other.m_has_value)
{
if (m_has_value) {
new (&m_storage) T(other.value_without_consume_state());
}
}
RETURN_TYPESTATE(unknown)
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;
}
RETURN_TYPESTATE(unknown)
Optional& operator=(Optional&& other)
{
if (this != &other) {
clear();
m_has_value = other.m_has_value;
if (m_has_value) {
new (&m_storage) T(other.release_value());
}
}
return *this;
}
~Optional()
{
clear();
}
void clear()
{
if (m_has_value) {
value().~T();
m_has_value = false;
}
}
SET_TYPESTATE(consumed)
bool has_value() const { return m_has_value; }
CALLABLE_WHEN(consumed)
T& value()
{
ASSERT(m_has_value);
return *reinterpret_cast<T*>(&m_storage);
}
CALLABLE_WHEN(consumed)
const T& value() const
{
return value_without_consume_state();
}
CALLABLE_WHEN(consumed)
T release_value()
{
ASSERT(m_has_value);
T released_value = move(value());
value().~T();
return released_value;
}
T value_or(const T& fallback) const
{
if (m_has_value)
return value();
return fallback;
}
operator bool() const { return m_has_value; }
private:
// Call when we don't want to alter the consume state
const T& value_without_consume_state() const
{
ASSERT(m_has_value);
return *reinterpret_cast<const T*>(&m_storage);
}
char m_storage[sizeof(T)];
bool m_has_value { false };
};
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