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62f84e94c8
If a non-const lvalue reference is passed to these constructors, the converting constructor will be selected instead of the desired copy/move constructor. Since I needed to touch `KResultOr` anyway, I made the forwarding converting constructor use `forward<U>` instead of `move`. This meant that previously, if a lvalue was passed to it, a move operation took place even if no `move()` was called on it. Member initializers and if-else statements have been changed to match our current coding style.
175 lines
3.9 KiB
C++
175 lines
3.9 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Assertions.h>
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#include <AK/Format.h>
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#include <AK/Platform.h>
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#include <AK/StdLibExtras.h>
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#include <LibC/errno_numbers.h>
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namespace Kernel {
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enum KSuccessTag {
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KSuccess
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};
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class [[nodiscard]] KResult {
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public:
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KResult(ErrnoCode error)
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: m_error(-error)
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{
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}
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KResult(KSuccessTag)
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: m_error(0)
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{
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}
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operator int() const { return m_error; }
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[[nodiscard]] int error() const { return m_error; }
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[[nodiscard]] bool is_success() const { return m_error == 0; }
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[[nodiscard]] bool is_error() const { return !is_success(); }
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private:
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template<typename T>
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friend class KResultOr;
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KResult() = default;
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int m_error { 0 };
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};
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template<typename T>
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class [[nodiscard]] KResultOr {
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public:
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KResultOr(KResult error)
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: m_error(error)
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, m_is_error(true)
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{
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}
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KResultOr(ErrnoCode error)
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: m_error(error)
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, m_is_error(true)
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{
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}
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ALWAYS_INLINE KResultOr(T&& value)
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: m_have_storage(true)
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{
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new (&m_storage) T(move(value));
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}
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ALWAYS_INLINE KResultOr(const T& value)
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: m_have_storage(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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ALWAYS_INLINE KResultOr(U&& value) requires(!IsSame<RemoveCVReference<U>, KResultOr<T>>)
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: m_have_storage(true)
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{
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new (&m_storage) T(forward<U>(value));
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}
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KResultOr(KResultOr&& other)
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{
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m_is_error = other.m_is_error;
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if (m_is_error) {
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m_error = other.m_error;
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} else {
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if (other.m_have_storage) {
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new (&m_storage) T(move(other.value()));
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m_have_storage = true;
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other.value().~T();
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other.m_have_storage = false;
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}
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}
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other.m_is_error = true;
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other.m_error = KSuccess;
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}
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KResultOr& operator=(KResultOr&& other)
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{
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if (&other == this)
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return *this;
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if (!m_is_error && m_have_storage) {
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value().~T();
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m_have_storage = false;
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}
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m_is_error = other.m_is_error;
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if (m_is_error) {
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m_error = other.m_error;
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} else {
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if (other.m_have_storage) {
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new (&m_storage) T(move(other.value()));
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m_have_storage = true;
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other.value().~T();
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other.m_have_storage = false;
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}
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}
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other.m_is_error = true;
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other.m_error = KSuccess;
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return *this;
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}
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~KResultOr()
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{
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if (!m_is_error && m_have_storage)
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value().~T();
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}
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[[nodiscard]] bool is_error() const { return m_is_error; }
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[[nodiscard]] ALWAYS_INLINE KResult error() const
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{
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VERIFY(m_is_error);
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return m_error;
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}
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[[nodiscard]] KResult result() const { return m_is_error ? m_error : KSuccess; }
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[[nodiscard]] ALWAYS_INLINE T& value()
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{
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VERIFY(!m_is_error);
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return *reinterpret_cast<T*>(&m_storage);
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}
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[[nodiscard]] ALWAYS_INLINE const T& value() const
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{
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VERIFY(!m_is_error);
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return *reinterpret_cast<T*>(&m_storage);
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}
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[[nodiscard]] ALWAYS_INLINE T release_value()
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{
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VERIFY(!m_is_error);
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VERIFY(m_have_storage);
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T released_value(move(*reinterpret_cast<T*>(&m_storage)));
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value().~T();
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m_have_storage = false;
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return released_value;
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}
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private:
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union {
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alignas(T) char m_storage[sizeof(T)];
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KResult m_error;
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};
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bool m_is_error { false };
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bool m_have_storage { false };
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};
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}
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template<>
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struct AK::Formatter<Kernel::KResult> : Formatter<int> {
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void format(FormatBuilder& builder, Kernel::KResult value)
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{
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return Formatter<int>::format(builder, value);
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}
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};
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