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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Format.h>
#include <AK/Platform.h>
#include <AK/StdLibExtras.h>
#include <LibC/errno_numbers.h>
namespace Kernel {
enum KSuccessTag {
KSuccess
};
class [[nodiscard]] KResult {
public:
KResult(ErrnoCode error)
: m_error(-error)
{
}
KResult(KSuccessTag)
: m_error(0)
{
}
[[nodiscard]] int error() const { return m_error; }
[[nodiscard]] bool is_success() const { return m_error == 0; }
[[nodiscard]] bool is_error() const { return !is_success(); }
bool operator==(ErrnoCode error) const { return is_error() && m_error == -error; }
bool operator!=(ErrnoCode error) const { return !is_error() || m_error != -error; }
bool operator!=(KSuccessTag) const { return is_error(); }
bool operator==(KSuccessTag) const { return !is_error(); }
private:
template<typename T>
friend class KResultOr;
KResult() = default;
int m_error { 0 };
};
template<typename T>
class [[nodiscard]] KResultOr {
public:
KResultOr(KResult error)
: m_error(error)
, m_is_error(true)
{
}
KResultOr(ErrnoCode error)
: m_error(error)
, m_is_error(true)
{
}
ALWAYS_INLINE KResultOr(T&& value)
: m_have_storage(true)
{
new (&m_storage) T(move(value));
}
ALWAYS_INLINE KResultOr(const T& value)
: m_have_storage(true)
{
new (&m_storage) T(value);
}
template<typename U>
ALWAYS_INLINE KResultOr(U&& value) requires(!IsSame<RemoveCVReference<U>, KResultOr<T>>)
: m_have_storage(true)
{
new (&m_storage) T(forward<U>(value));
}
KResultOr(KResultOr&& other)
{
m_is_error = other.m_is_error;
if (m_is_error) {
m_error = other.m_error;
} else {
if (other.m_have_storage) {
new (&m_storage) T(move(other.value()));
m_have_storage = true;
other.value().~T();
other.m_have_storage = false;
}
}
other.m_is_error = true;
other.m_error = KSuccess;
}
KResultOr& operator=(KResultOr&& other)
{
if (&other == this)
return *this;
if (!m_is_error && m_have_storage) {
value().~T();
m_have_storage = false;
}
m_is_error = other.m_is_error;
if (m_is_error) {
m_error = other.m_error;
} else {
if (other.m_have_storage) {
new (&m_storage) T(move(other.value()));
m_have_storage = true;
other.value().~T();
other.m_have_storage = false;
}
}
other.m_is_error = true;
other.m_error = KSuccess;
return *this;
}
~KResultOr()
{
if (!m_is_error && m_have_storage)
value().~T();
}
[[nodiscard]] bool is_error() const { return m_is_error; }
[[nodiscard]] ALWAYS_INLINE KResult error() const
{
VERIFY(m_is_error);
return m_error;
}
[[nodiscard]] KResult result() const { return m_is_error ? m_error : KSuccess; }
[[nodiscard]] ALWAYS_INLINE T& value() &
{
VERIFY(!m_is_error);
return *reinterpret_cast<T*>(&m_storage);
}
[[nodiscard]] ALWAYS_INLINE T const& value() const&
{
VERIFY(!m_is_error);
return *reinterpret_cast<T*>(&m_storage);
}
T value() && = delete;
[[nodiscard]] ALWAYS_INLINE T release_value()
{
VERIFY(!m_is_error);
VERIFY(m_have_storage);
T released_value(move(*reinterpret_cast<T*>(&m_storage)));
value().~T();
m_have_storage = false;
return released_value;
}
[[nodiscard]] KResult release_error()
{
VERIFY(m_is_error);
return m_error;
}
private:
union {
alignas(T) char m_storage[sizeof(T)];
KResult m_error;
};
bool m_is_error { false };
bool m_have_storage { false };
};
}
using Kernel::KResult;
using Kernel::KResultOr;
using Kernel::KSuccess;
template<>
struct AK::Formatter<KResult> : Formatter<FormatString> {
void format(FormatBuilder& builder, Kernel::KResult value)
{
if (value.is_error())
return AK::Formatter<FormatString>::format(builder, "KResult({})", value.error());
return AK::Formatter<FormatString>::format(builder, "KResult(success)");
}
};
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