mirror of
https://github.com/SerenityOS/serenity
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171 lines
4.4 KiB
C++
171 lines
4.4 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Platform.h>
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#include <AK/StdLibExtras.h>
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#include <AK/Types.h>
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namespace AK {
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template<typename T>
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class alignas(T) [[nodiscard]] Optional
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{
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public:
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Optional() { }
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Optional(const T& value)
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: m_has_value(true)
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{
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new (&m_storage) T(value);
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}
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template<typename U>
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Optional(const U& value)
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: m_has_value(true)
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{
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new (&m_storage) T(value);
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}
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Optional(T && value)
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: m_has_value(true)
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{
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new (&m_storage) T(move(value));
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}
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Optional(Optional && other)
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: m_has_value(other.m_has_value)
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{
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if (other.has_value()) {
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new (&m_storage) T(other.release_value());
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other.m_has_value = false;
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}
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}
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Optional(const Optional& other)
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: m_has_value(other.m_has_value)
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{
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if (m_has_value) {
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new (&m_storage) T(other.value_without_consume_state());
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}
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}
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Optional& operator=(const Optional& other)
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{
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if (this != &other) {
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clear();
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m_has_value = other.m_has_value;
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if (m_has_value) {
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new (&m_storage) T(other.value());
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}
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}
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return *this;
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}
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Optional& operator=(Optional&& other)
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{
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if (this != &other) {
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clear();
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m_has_value = other.m_has_value;
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if (other.has_value())
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new (&m_storage) T(other.release_value());
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}
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return *this;
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}
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template<typename O>
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bool operator==(const Optional<O>& other) const
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{
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return has_value() == other.has_value() && (!has_value() || value() == other.value());
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}
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ALWAYS_INLINE ~Optional()
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{
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clear();
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}
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ALWAYS_INLINE void clear()
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{
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if (m_has_value) {
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value().~T();
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m_has_value = false;
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}
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}
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template<typename... Parameters>
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ALWAYS_INLINE void emplace(Parameters && ... parameters)
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{
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clear();
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m_has_value = true;
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new (&m_storage) T(forward<Parameters>(parameters)...);
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}
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ALWAYS_INLINE bool has_value() const { return m_has_value; }
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ALWAYS_INLINE T& value()
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{
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ASSERT(m_has_value);
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return *reinterpret_cast<T*>(&m_storage);
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}
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ALWAYS_INLINE const T& value() const
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{
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return value_without_consume_state();
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}
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T release_value()
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{
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ASSERT(m_has_value);
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T released_value = move(value());
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value().~T();
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m_has_value = false;
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return released_value;
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}
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ALWAYS_INLINE T value_or(const T& fallback) const
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{
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if (m_has_value)
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return value();
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return fallback;
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}
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private:
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// Call when we don't want to alter the consume state
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ALWAYS_INLINE const T& value_without_consume_state() const
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{
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ASSERT(m_has_value);
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return *reinterpret_cast<const T*>(&m_storage);
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}
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u8 m_storage[sizeof(T)] { 0 };
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bool m_has_value { false };
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};
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}
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using AK::Optional;
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