mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-11-26 17:40:27 +00:00
aaf54f8cf8
This is an extension of cc0b970d but for the reference-handling
specialization of Optional.
This basically allow us to write code like:
```cpp
Optional<u8&> opt;
opt = OptionalNone{};
```
567 lines
16 KiB
C++
567 lines
16 KiB
C++
/*
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* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
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* Copyright (c) 2021, Daniel Bertalan <dani@danielbertalan.dev>
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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/StdLibExtras.h>
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#include <AK/Try.h>
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#include <AK/Types.h>
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#include <AK/kmalloc.h>
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namespace AK {
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namespace Detail {
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template<auto condition, typename T>
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struct ConditionallyResultType;
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template<typename T>
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struct ConditionallyResultType<true, T> {
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using Type = typename T::ResultType;
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};
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template<typename T>
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struct ConditionallyResultType<false, T> {
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using Type = T;
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};
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}
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template<auto condition, typename T>
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using ConditionallyResultType = typename Detail::ConditionallyResultType<condition, T>::Type;
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// NOTE: If you're here because of an internal compiler error in GCC 10.3.0+,
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// it's because of the following bug:
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//
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// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96745
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//
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// Make sure you didn't accidentally make your destructor private before
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// you start bug hunting. :^)
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template<typename>
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class Optional;
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struct OptionalNone {
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explicit OptionalNone() = default;
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};
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template<typename T>
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requires(!IsLvalueReference<T>) class [[nodiscard]] Optional<T> {
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template<typename U>
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friend class Optional;
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static_assert(!IsLvalueReference<T> && !IsRvalueReference<T>);
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public:
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using ValueType = T;
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ALWAYS_INLINE Optional() = default;
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template<SameAs<OptionalNone> V>
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Optional(V) { }
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template<SameAs<OptionalNone> V>
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Optional& operator=(V)
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{
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clear();
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return *this;
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}
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#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
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Optional(Optional const& other)
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requires(!IsCopyConstructible<T>)
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= delete;
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Optional(Optional const& other) = default;
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Optional(Optional&& other)
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requires(!IsMoveConstructible<T>)
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= delete;
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Optional& operator=(Optional const&)
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requires(!IsCopyConstructible<T> || !IsDestructible<T>)
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= delete;
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Optional& operator=(Optional const&) = default;
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Optional& operator=(Optional&& other)
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requires(!IsMoveConstructible<T> || !IsDestructible<T>)
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= delete;
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~Optional()
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requires(!IsDestructible<T>)
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= delete;
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~Optional() = default;
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#endif
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ALWAYS_INLINE Optional(Optional const& other)
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#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
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requires(!IsTriviallyCopyConstructible<T>)
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#endif
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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.value());
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}
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ALWAYS_INLINE 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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}
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template<typename U>
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requires(IsConstructible<T, U const&> && !IsSpecializationOf<T, Optional> && !IsSpecializationOf<U, Optional>) ALWAYS_INLINE explicit Optional(Optional<U> const& 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.value());
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}
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template<typename U>
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requires(IsConstructible<T, U &&> && !IsSpecializationOf<T, Optional> && !IsSpecializationOf<U, Optional>) ALWAYS_INLINE explicit Optional(Optional<U>&& 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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}
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template<typename U = T>
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requires(!IsSame<OptionalNone, RemoveCVReference<U>>)
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ALWAYS_INLINE explicit(!IsConvertible<U&&, T>) Optional(U&& value)
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requires(!IsSame<RemoveCVReference<U>, Optional<T>> && IsConstructible<T, U &&>)
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: m_has_value(true)
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{
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new (&m_storage) T(forward<U>(value));
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}
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ALWAYS_INLINE Optional& operator=(Optional const& other)
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#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
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requires(!IsTriviallyCopyConstructible<T> || !IsTriviallyDestructible<T>)
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#endif
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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.value());
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}
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}
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return *this;
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}
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ALWAYS_INLINE 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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}
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return *this;
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}
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template<typename O>
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ALWAYS_INLINE bool operator==(Optional<O> const& 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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template<typename O>
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ALWAYS_INLINE bool operator==(O const& other) const
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{
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return has_value() && value() == other;
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}
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ALWAYS_INLINE ~Optional()
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#ifdef AK_HAS_CONDITIONALLY_TRIVIAL
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requires(!IsTriviallyDestructible<T>)
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#endif
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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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template<typename Callable>
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ALWAYS_INLINE void lazy_emplace(Callable callable)
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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 { callable() };
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}
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[[nodiscard]] ALWAYS_INLINE bool has_value() const { return m_has_value; }
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[[nodiscard]] ALWAYS_INLINE T& value() &
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{
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VERIFY(m_has_value);
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return *__builtin_launder(reinterpret_cast<T*>(&m_storage));
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}
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[[nodiscard]] ALWAYS_INLINE T const& value() const&
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{
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VERIFY(m_has_value);
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return *__builtin_launder(reinterpret_cast<T const*>(&m_storage));
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}
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[[nodiscard]] ALWAYS_INLINE T value() &&
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{
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return release_value();
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}
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[[nodiscard]] ALWAYS_INLINE T release_value()
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{
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VERIFY(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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[[nodiscard]] ALWAYS_INLINE T value_or(T const& 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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[[nodiscard]] ALWAYS_INLINE T value_or(T&& fallback) &&
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{
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if (m_has_value)
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return move(value());
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return move(fallback);
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE T value_or_lazy_evaluated(Callback callback) const
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{
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if (m_has_value)
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return value();
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return callback();
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE Optional<T> value_or_lazy_evaluated_optional(Callback callback) const
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{
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if (m_has_value)
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return value();
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return callback();
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE ErrorOr<T> try_value_or_lazy_evaluated(Callback callback) const
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{
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if (m_has_value)
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return value();
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return TRY(callback());
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE ErrorOr<Optional<T>> try_value_or_lazy_evaluated_optional(Callback callback) const
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{
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if (m_has_value)
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return value();
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return TRY(callback());
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}
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ALWAYS_INLINE T const& operator*() const { return value(); }
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ALWAYS_INLINE T& operator*() { return value(); }
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ALWAYS_INLINE T const* operator->() const { return &value(); }
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ALWAYS_INLINE T* operator->() { return &value(); }
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template<typename F, typename MappedType = decltype(declval<F>()(declval<T&>())), auto IsErrorOr = IsSpecializationOf<MappedType, ErrorOr>, typename OptionalType = Optional<ConditionallyResultType<IsErrorOr, MappedType>>>
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ALWAYS_INLINE Conditional<IsErrorOr, ErrorOr<OptionalType>, OptionalType> map(F&& mapper)
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{
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if constexpr (IsErrorOr) {
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if (m_has_value)
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return OptionalType { TRY(mapper(value())) };
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return OptionalType {};
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} else {
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if (m_has_value)
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return OptionalType { mapper(value()) };
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return OptionalType {};
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}
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}
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template<typename F, typename MappedType = decltype(declval<F>()(declval<T&>())), auto IsErrorOr = IsSpecializationOf<MappedType, ErrorOr>, typename OptionalType = Optional<ConditionallyResultType<IsErrorOr, MappedType>>>
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ALWAYS_INLINE Conditional<IsErrorOr, ErrorOr<OptionalType>, OptionalType> map(F&& mapper) const
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{
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if constexpr (IsErrorOr) {
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if (m_has_value)
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return OptionalType { TRY(mapper(value())) };
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return OptionalType {};
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} else {
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if (m_has_value)
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return OptionalType { mapper(value()) };
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return OptionalType {};
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}
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}
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static FlatPtr value_offset() { return OFFSET_OF(Optional, m_storage); }
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static FlatPtr has_value_offset() { return OFFSET_OF(Optional, m_has_value); }
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private:
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alignas(T) u8 m_storage[sizeof(T)];
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bool m_has_value { false };
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};
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template<typename T>
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requires(IsLvalueReference<T>) class [[nodiscard]] Optional<T> {
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template<typename>
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friend class Optional;
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template<typename U>
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constexpr static bool CanBePlacedInOptional = IsSame<RemoveReference<T>, RemoveReference<AddConstToReferencedType<U>>> && (IsBaseOf<RemoveCVReference<T>, RemoveCVReference<U>> || IsSame<RemoveCVReference<T>, RemoveCVReference<U>>);
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public:
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using ValueType = T;
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ALWAYS_INLINE Optional() = default;
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template<SameAs<OptionalNone> V>
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Optional(V) { }
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template<SameAs<OptionalNone> V>
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Optional& operator=(V)
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{
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clear();
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return *this;
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}
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template<typename U = T>
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ALWAYS_INLINE Optional(U& value)
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requires(CanBePlacedInOptional<U&>)
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: m_pointer(&value)
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{
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}
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ALWAYS_INLINE Optional(RemoveReference<T>& value)
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: m_pointer(&value)
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{
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}
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ALWAYS_INLINE Optional(Optional const& other)
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: m_pointer(other.m_pointer)
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{
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}
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ALWAYS_INLINE Optional(Optional&& other)
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: m_pointer(other.m_pointer)
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{
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other.m_pointer = nullptr;
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}
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template<typename U>
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ALWAYS_INLINE Optional(Optional<U> const& other)
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requires(CanBePlacedInOptional<U>)
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: m_pointer(other.m_pointer)
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{
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}
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template<typename U>
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ALWAYS_INLINE Optional(Optional<U>&& other)
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requires(CanBePlacedInOptional<U>)
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: m_pointer(other.m_pointer)
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{
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other.m_pointer = nullptr;
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}
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ALWAYS_INLINE Optional& operator=(Optional const& other)
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{
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m_pointer = other.m_pointer;
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return *this;
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}
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ALWAYS_INLINE Optional& operator=(Optional&& other)
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{
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m_pointer = other.m_pointer;
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other.m_pointer = nullptr;
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return *this;
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}
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template<typename U>
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ALWAYS_INLINE Optional& operator=(Optional<U> const& other)
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requires(CanBePlacedInOptional<U>)
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{
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m_pointer = other.m_pointer;
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return *this;
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}
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template<typename U>
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ALWAYS_INLINE Optional& operator=(Optional<U>&& other)
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requires(CanBePlacedInOptional<U>)
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{
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m_pointer = other.m_pointer;
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other.m_pointer = nullptr;
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return *this;
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}
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// Note: Disallows assignment from a temporary as this does not do any lifetime extension.
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template<typename U>
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requires(!IsSame<OptionalNone, RemoveCVReference<U>>)
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ALWAYS_INLINE Optional& operator=(U&& value)
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requires(CanBePlacedInOptional<U> && IsLvalueReference<U>)
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{
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m_pointer = &value;
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return *this;
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}
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ALWAYS_INLINE void clear()
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{
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m_pointer = nullptr;
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}
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[[nodiscard]] ALWAYS_INLINE bool has_value() const { return m_pointer != nullptr; }
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[[nodiscard]] ALWAYS_INLINE T value()
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{
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VERIFY(m_pointer);
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return *m_pointer;
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}
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[[nodiscard]] ALWAYS_INLINE AddConstToReferencedType<T> value() const
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{
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VERIFY(m_pointer);
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return *m_pointer;
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}
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template<typename U>
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requires(IsBaseOf<RemoveCVReference<T>, U>) [[nodiscard]] ALWAYS_INLINE AddConstToReferencedType<T> value_or(U& fallback) const
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{
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if (m_pointer)
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return value();
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return fallback;
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}
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// Note that this ends up copying the value.
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[[nodiscard]] ALWAYS_INLINE RemoveCVReference<T> value_or(RemoveCVReference<T> fallback) const
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{
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if (m_pointer)
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return value();
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return fallback;
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}
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[[nodiscard]] ALWAYS_INLINE T release_value()
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{
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return *exchange(m_pointer, nullptr);
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}
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template<typename U>
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ALWAYS_INLINE bool operator==(Optional<U> const& 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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template<typename U>
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ALWAYS_INLINE bool operator==(U const& other) const
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{
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return has_value() && value() == other;
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}
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ALWAYS_INLINE AddConstToReferencedType<T> operator*() const { return value(); }
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ALWAYS_INLINE T operator*() { return value(); }
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ALWAYS_INLINE RawPtr<AddConst<RemoveReference<T>>> operator->() const { return &value(); }
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ALWAYS_INLINE RawPtr<RemoveReference<T>> operator->() { return &value(); }
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// Conversion operators from Optional<T&> -> Optional<T>
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ALWAYS_INLINE operator Optional<RemoveCVReference<T>>() const
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{
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if (has_value())
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return Optional<RemoveCVReference<T>>(value());
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return {};
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE T value_or_lazy_evaluated(Callback callback) const
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{
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if (m_pointer != nullptr)
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return value();
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return callback();
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE Optional<T> value_or_lazy_evaluated_optional(Callback callback) const
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{
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if (m_pointer != nullptr)
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return value();
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return callback();
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE ErrorOr<T> try_value_or_lazy_evaluated(Callback callback) const
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{
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if (m_pointer != nullptr)
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return value();
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return TRY(callback());
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}
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template<typename Callback>
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[[nodiscard]] ALWAYS_INLINE ErrorOr<Optional<T>> try_value_or_lazy_evaluated_optional(Callback callback) const
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{
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if (m_pointer != nullptr)
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return value();
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return TRY(callback());
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}
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template<typename F, typename MappedType = decltype(declval<F>()(declval<T&>())), auto IsErrorOr = IsSpecializationOf<MappedType, ErrorOr>, typename OptionalType = Optional<ConditionallyResultType<IsErrorOr, MappedType>>>
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ALWAYS_INLINE Conditional<IsErrorOr, ErrorOr<OptionalType>, OptionalType> map(F&& mapper)
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{
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if constexpr (IsErrorOr) {
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if (m_pointer != nullptr)
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return OptionalType { TRY(mapper(value())) };
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return OptionalType {};
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} else {
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if (m_pointer != nullptr)
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return OptionalType { mapper(value()) };
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return OptionalType {};
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}
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}
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template<typename F, typename MappedType = decltype(declval<F>()(declval<T&>())), auto IsErrorOr = IsSpecializationOf<MappedType, ErrorOr>, typename OptionalType = Optional<ConditionallyResultType<IsErrorOr, MappedType>>>
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ALWAYS_INLINE Conditional<IsErrorOr, ErrorOr<OptionalType>, OptionalType> map(F&& mapper) const
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{
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if constexpr (IsErrorOr) {
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if (m_pointer != nullptr)
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return OptionalType { TRY(mapper(value())) };
|
|
return OptionalType {};
|
|
} else {
|
|
if (m_pointer != nullptr)
|
|
return OptionalType { mapper(value()) };
|
|
|
|
return OptionalType {};
|
|
}
|
|
}
|
|
|
|
private:
|
|
RemoveReference<T>* m_pointer { nullptr };
|
|
};
|
|
|
|
}
|
|
|
|
#if USING_AK_GLOBALLY
|
|
using AK::Optional;
|
|
using AK::OptionalNone;
|
|
#endif
|