78 lines
1.9 KiB
C++
78 lines
1.9 KiB
C++
/*
|
|
Minetest
|
|
Copyright (C) 2021 rubenwardy
|
|
|
|
This program is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU Lesser General Public License as published by
|
|
the Free Software Foundation; either version 2.1 of the License, or
|
|
(at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public License along
|
|
with this program; if not, write to the Free Software Foundation, Inc.,
|
|
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "debug.h"
|
|
|
|
struct nullopt_t
|
|
{
|
|
};
|
|
constexpr nullopt_t nullopt{};
|
|
|
|
/**
|
|
* An implementation of optional for C++11, which aims to be
|
|
* compatible with a subset of std::optional features.
|
|
*
|
|
* Unfortunately, Minetest doesn't use C++17 yet.
|
|
*
|
|
* @tparam T The type to be stored
|
|
*/
|
|
template <typename T>
|
|
class Optional
|
|
{
|
|
bool m_has_value = false;
|
|
T m_value;
|
|
|
|
public:
|
|
Optional() noexcept {}
|
|
Optional(nullopt_t) noexcept {}
|
|
Optional(const T &value) noexcept : m_has_value(true), m_value(value) {}
|
|
Optional(const Optional<T> &other) noexcept :
|
|
m_has_value(other.m_has_value), m_value(other.m_value)
|
|
{
|
|
}
|
|
|
|
void operator=(nullopt_t) noexcept { m_has_value = false; }
|
|
|
|
void operator=(const Optional<T> &other) noexcept
|
|
{
|
|
m_has_value = other.m_has_value;
|
|
m_value = other.m_value;
|
|
}
|
|
|
|
T &value()
|
|
{
|
|
FATAL_ERROR_IF(!m_has_value, "optional doesn't have value");
|
|
return m_value;
|
|
}
|
|
|
|
const T &value() const
|
|
{
|
|
FATAL_ERROR_IF(!m_has_value, "optional doesn't have value");
|
|
return m_value;
|
|
}
|
|
|
|
const T &value_or(const T &def) const { return m_has_value ? m_value : def; }
|
|
|
|
bool has_value() const noexcept { return m_has_value; }
|
|
|
|
explicit operator bool() const { return m_has_value; }
|
|
};
|