| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef THIRD_PARTY_BASE_OPTIONAL_H_ |
| #define THIRD_PARTY_BASE_OPTIONAL_H_ |
| |
| #include <functional> |
| #include <type_traits> |
| #include <utility> |
| |
| #include "third_party/base/logging.h" |
| #include "third_party/base/template_util.h" |
| |
| namespace pdfium { |
| |
| // Specification: |
| // http://en.cppreference.com/w/cpp/utility/optional/nullopt_t |
| struct nullopt_t { |
| constexpr explicit nullopt_t(int) {} |
| }; |
| |
| // Specification: |
| // http://en.cppreference.com/w/cpp/utility/optional/nullopt |
| constexpr nullopt_t nullopt(0); |
| |
| // Forward declaration, which is refered by following helpers. |
| template <typename T> |
| class Optional; |
| |
| namespace internal { |
| |
| struct DummyUnionMember {}; |
| |
| template <typename T, bool = std::is_trivially_destructible<T>::value> |
| struct OptionalStorageBase { |
| // Provide non-defaulted default ctor to make sure it's not deleted by |
| // non-trivial T::T() in the union. |
| constexpr OptionalStorageBase() : dummy_() {} |
| |
| template <class... Args> |
| constexpr explicit OptionalStorageBase(in_place_t, Args&&... args) |
| : is_populated_(true), value_(std::forward<Args>(args)...) {} |
| |
| // When T is not trivially destructible we must call its |
| // destructor before deallocating its memory. |
| // Note that this hides the (implicitly declared) move constructor, which |
| // would be used for constexpr move constructor in OptionalStorage<T>. |
| // It is needed iff T is trivially move constructible. However, the current |
| // is_trivially_{copy,move}_constructible implementation requires |
| // is_trivially_destructible (which looks a bug, cf: |
| // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51452 and |
| // http://cplusplus.github.io/LWG/lwg-active.html#2116), so it is not |
| // necessary for this case at the moment. Please see also the destructor |
| // comment in "is_trivially_destructible = true" specialization below. |
| ~OptionalStorageBase() { |
| if (is_populated_) |
| value_.~T(); |
| } |
| |
| template <class... Args> |
| void Init(Args&&... args) { |
| DCHECK(!is_populated_); |
| ::new (&value_) T(std::forward<Args>(args)...); |
| is_populated_ = true; |
| } |
| |
| bool is_populated_ = false; |
| union { |
| // |dummy_| exists so that the union will always be initialized, even when |
| // it doesn't contain a value. Union members must be initialized for the |
| // constructor to be 'constexpr'. Having a special trivial class for it is |
| // better than e.g. using char, because the latter will have to be |
| // zero-initialized, and the compiler can't optimize this write away, since |
| // it assumes this might be a programmer's invariant. This can also cause |
| // problems for conservative GC in Oilpan. Compiler is free to split shared |
| // and non-shared parts of the union in separate memory locations (or |
| // registers). If conservative GC is triggered at this moment, the stack |
| // scanning routine won't find the correct object pointed from |
| // Optional<HeapObject*>. This dummy valueless struct lets the compiler know |
| // that we don't care about the value of this union member. |
| DummyUnionMember dummy_; |
| T value_; |
| }; |
| }; |
| |
| template <typename T> |
| struct OptionalStorageBase<T, true /* trivially destructible */> { |
| // Provide non-defaulted default ctor to make sure it's not deleted by |
| // non-trivial T::T() in the union. |
| constexpr OptionalStorageBase() : dummy_() {} |
| |
| template <class... Args> |
| constexpr explicit OptionalStorageBase(in_place_t, Args&&... args) |
| : is_populated_(true), value_(std::forward<Args>(args)...) {} |
| |
| // When T is trivially destructible (i.e. its destructor does nothing) there |
| // is no need to call it. Implicitly defined destructor is trivial, because |
| // both members (bool and union containing only variants which are trivially |
| // destructible) are trivially destructible. |
| // Explicitly-defaulted destructor is also trivial, but do not use it here, |
| // because it hides the implicit move constructor. It is needed to implement |
| // constexpr move constructor in OptionalStorage iff T is trivially move |
| // constructible. Note that, if T is trivially move constructible, the move |
| // constructor of OptionalStorageBase<T> is also implicitly defined and it is |
| // trivially move constructor. If T is not trivially move constructible, |
| // "not declaring move constructor without destructor declaration" here means |
| // "delete move constructor", which works because any move constructor of |
| // OptionalStorage will not refer to it in that case. |
| |
| template <class... Args> |
| void Init(Args&&... args) { |
| DCHECK(!is_populated_); |
| ::new (&value_) T(std::forward<Args>(args)...); |
| is_populated_ = true; |
| } |
| |
| bool is_populated_ = false; |
| union { |
| // |dummy_| exists so that the union will always be initialized, even when |
| // it doesn't contain a value. Union members must be initialized for the |
| // constructor to be 'constexpr'. Having a special trivial class for it is |
| // better than e.g. using char, because the latter will have to be |
| // zero-initialized, and the compiler can't optimize this write away, since |
| // it assumes this might be a programmer's invariant. This can also cause |
| // problems for conservative GC in Oilpan. Compiler is free to split shared |
| // and non-shared parts of the union in separate memory locations (or |
| // registers). If conservative GC is triggered at this moment, the stack |
| // scanning routine won't find the correct object pointed from |
| // Optional<HeapObject*>. This dummy valueless struct lets the compiler know |
| // that we don't care about the value of this union member. |
| DummyUnionMember dummy_; |
| T value_; |
| }; |
| }; |
| |
| // Implement conditional constexpr copy and move constructors. These are |
| // constexpr if is_trivially_{copy,move}_constructible<T>::value is true |
| // respectively. If each is true, the corresponding constructor is defined as |
| // "= default;", which generates a constexpr constructor (In this case, |
| // the condition of constexpr-ness is satisfied because the base class also has |
| // compiler generated constexpr {copy,move} constructors). Note that |
| // placement-new is prohibited in constexpr. |
| template <typename T, |
| bool = is_trivially_copy_constructible<T>::value, |
| bool = std::is_trivially_move_constructible<T>::value> |
| struct OptionalStorage : OptionalStorageBase<T> { |
| // This is no trivially {copy,move} constructible case. Other cases are |
| // defined below as specializations. |
| |
| // Accessing the members of template base class requires explicit |
| // declaration. |
| using OptionalStorageBase<T>::is_populated_; |
| using OptionalStorageBase<T>::value_; |
| using OptionalStorageBase<T>::Init; |
| |
| // Inherit constructors (specifically, the in_place constructor). |
| using OptionalStorageBase<T>::OptionalStorageBase; |
| |
| // User defined constructor deletes the default constructor. |
| // Define it explicitly. |
| OptionalStorage() = default; |
| |
| OptionalStorage(const OptionalStorage& other) { |
| if (other.is_populated_) |
| Init(other.value_); |
| } |
| |
| OptionalStorage(OptionalStorage&& other) noexcept( |
| std::is_nothrow_move_constructible<T>::value) { |
| if (other.is_populated_) |
| Init(std::move(other.value_)); |
| } |
| }; |
| |
| template <typename T> |
| struct OptionalStorage<T, |
| true /* trivially copy constructible */, |
| false /* trivially move constructible */> |
| : OptionalStorageBase<T> { |
| using OptionalStorageBase<T>::is_populated_; |
| using OptionalStorageBase<T>::value_; |
| using OptionalStorageBase<T>::Init; |
| using OptionalStorageBase<T>::OptionalStorageBase; |
| |
| OptionalStorage() = default; |
| OptionalStorage(const OptionalStorage& other) = default; |
| |
| OptionalStorage(OptionalStorage&& other) noexcept( |
| std::is_nothrow_move_constructible<T>::value) { |
| if (other.is_populated_) |
| Init(std::move(other.value_)); |
| } |
| }; |
| |
| template <typename T> |
| struct OptionalStorage<T, |
| false /* trivially copy constructible */, |
| true /* trivially move constructible */> |
| : OptionalStorageBase<T> { |
| using OptionalStorageBase<T>::is_populated_; |
| using OptionalStorageBase<T>::value_; |
| using OptionalStorageBase<T>::Init; |
| using OptionalStorageBase<T>::OptionalStorageBase; |
| |
| OptionalStorage() = default; |
| OptionalStorage(OptionalStorage&& other) = default; |
| |
| OptionalStorage(const OptionalStorage& other) { |
| if (other.is_populated_) |
| Init(other.value_); |
| } |
| }; |
| |
| template <typename T> |
| struct OptionalStorage<T, |
| true /* trivially copy constructible */, |
| true /* trivially move constructible */> |
| : OptionalStorageBase<T> { |
| // If both trivially {copy,move} constructible are true, it is not necessary |
| // to use user-defined constructors. So, just inheriting constructors |
| // from the base class works. |
| using OptionalStorageBase<T>::OptionalStorageBase; |
| }; |
| |
| // Base class to support conditionally usable copy-/move- constructors |
| // and assign operators. |
| template <typename T> |
| class OptionalBase { |
| // This class provides implementation rather than public API, so everything |
| // should be hidden. Often we use composition, but we cannot in this case |
| // because of C++ language restriction. |
| protected: |
| constexpr OptionalBase() = default; |
| constexpr OptionalBase(const OptionalBase& other) = default; |
| constexpr OptionalBase(OptionalBase&& other) = default; |
| |
| template <class... Args> |
| constexpr explicit OptionalBase(in_place_t, Args&&... args) |
| : storage_(in_place, std::forward<Args>(args)...) {} |
| |
| // Implementation of converting constructors. |
| template <typename U> |
| explicit OptionalBase(const OptionalBase<U>& other) { |
| if (other.storage_.is_populated_) |
| storage_.Init(other.storage_.value_); |
| } |
| |
| template <typename U> |
| explicit OptionalBase(OptionalBase<U>&& other) { |
| if (other.storage_.is_populated_) |
| storage_.Init(std::move(other.storage_.value_)); |
| } |
| |
| ~OptionalBase() = default; |
| |
| OptionalBase& operator=(const OptionalBase& other) { |
| CopyAssign(other); |
| return *this; |
| } |
| |
| OptionalBase& operator=(OptionalBase&& other) noexcept( |
| std::is_nothrow_move_assignable<T>::value&& |
| std::is_nothrow_move_constructible<T>::value) { |
| MoveAssign(std::move(other)); |
| return *this; |
| } |
| |
| template <typename U> |
| void CopyAssign(const OptionalBase<U>& other) { |
| if (other.storage_.is_populated_) |
| InitOrAssign(other.storage_.value_); |
| else |
| FreeIfNeeded(); |
| } |
| |
| template <typename U> |
| void MoveAssign(OptionalBase<U>&& other) { |
| if (other.storage_.is_populated_) |
| InitOrAssign(std::move(other.storage_.value_)); |
| else |
| FreeIfNeeded(); |
| } |
| |
| template <typename U> |
| void InitOrAssign(U&& value) { |
| if (storage_.is_populated_) |
| storage_.value_ = std::forward<U>(value); |
| else |
| storage_.Init(std::forward<U>(value)); |
| } |
| |
| void FreeIfNeeded() { |
| if (!storage_.is_populated_) |
| return; |
| storage_.value_.~T(); |
| storage_.is_populated_ = false; |
| } |
| |
| // For implementing conversion, allow access to other typed OptionalBase |
| // class. |
| template <typename U> |
| friend class OptionalBase; |
| |
| OptionalStorage<T> storage_; |
| }; |
| |
| // The following {Copy,Move}{Constructible,Assignable} structs are helpers to |
| // implement constructor/assign-operator overloading. Specifically, if T is |
| // is not movable but copyable, Optional<T>'s move constructor should not |
| // participate in overload resolution. This inheritance trick implements that. |
| template <bool is_copy_constructible> |
| struct CopyConstructible {}; |
| |
| template <> |
| struct CopyConstructible<false> { |
| constexpr CopyConstructible() = default; |
| constexpr CopyConstructible(const CopyConstructible&) = delete; |
| constexpr CopyConstructible(CopyConstructible&&) = default; |
| CopyConstructible& operator=(const CopyConstructible&) = default; |
| CopyConstructible& operator=(CopyConstructible&&) = default; |
| }; |
| |
| template <bool is_move_constructible> |
| struct MoveConstructible {}; |
| |
| template <> |
| struct MoveConstructible<false> { |
| constexpr MoveConstructible() = default; |
| constexpr MoveConstructible(const MoveConstructible&) = default; |
| constexpr MoveConstructible(MoveConstructible&&) = delete; |
| MoveConstructible& operator=(const MoveConstructible&) = default; |
| MoveConstructible& operator=(MoveConstructible&&) = default; |
| }; |
| |
| template <bool is_copy_assignable> |
| struct CopyAssignable {}; |
| |
| template <> |
| struct CopyAssignable<false> { |
| constexpr CopyAssignable() = default; |
| constexpr CopyAssignable(const CopyAssignable&) = default; |
| constexpr CopyAssignable(CopyAssignable&&) = default; |
| CopyAssignable& operator=(const CopyAssignable&) = delete; |
| CopyAssignable& operator=(CopyAssignable&&) = default; |
| }; |
| |
| template <bool is_move_assignable> |
| struct MoveAssignable {}; |
| |
| template <> |
| struct MoveAssignable<false> { |
| constexpr MoveAssignable() = default; |
| constexpr MoveAssignable(const MoveAssignable&) = default; |
| constexpr MoveAssignable(MoveAssignable&&) = default; |
| MoveAssignable& operator=(const MoveAssignable&) = default; |
| MoveAssignable& operator=(MoveAssignable&&) = delete; |
| }; |
| |
| // Helper to conditionally enable converting constructors and assign operators. |
| template <typename T, typename U> |
| using IsConvertibleFromOptional = |
| disjunction<std::is_constructible<T, Optional<U>&>, |
| std::is_constructible<T, const Optional<U>&>, |
| std::is_constructible<T, Optional<U>&&>, |
| std::is_constructible<T, const Optional<U>&&>, |
| std::is_convertible<Optional<U>&, T>, |
| std::is_convertible<const Optional<U>&, T>, |
| std::is_convertible<Optional<U>&&, T>, |
| std::is_convertible<const Optional<U>&&, T>>; |
| |
| template <typename T, typename U> |
| using IsAssignableFromOptional = |
| disjunction<IsConvertibleFromOptional<T, U>, |
| std::is_assignable<T&, Optional<U>&>, |
| std::is_assignable<T&, const Optional<U>&>, |
| std::is_assignable<T&, Optional<U>&&>, |
| std::is_assignable<T&, const Optional<U>&&>>; |
| |
| // Forward compatibility for C++17. |
| // Introduce one more deeper nested namespace to avoid leaking using std::swap. |
| namespace swappable_impl { |
| using std::swap; |
| |
| struct IsSwappableImpl { |
| // Tests if swap can be called. Check<T&>(0) returns true_type iff swap |
| // is available for T. Otherwise, Check's overload resolution falls back |
| // to Check(...) declared below thanks to SFINAE, so returns false_type. |
| template <typename T> |
| static auto Check(int) |
| -> decltype(swap(std::declval<T>(), std::declval<T>()), std::true_type()); |
| |
| template <typename T> |
| static std::false_type Check(...); |
| }; |
| } // namespace swappable_impl |
| |
| template <typename T> |
| struct IsSwappable : decltype(swappable_impl::IsSwappableImpl::Check<T&>(0)) {}; |
| |
| // Forward compatibility for C++20. |
| template <typename T> |
| using RemoveCvRefT = std::remove_cv_t<std::remove_reference_t<T>>; |
| |
| } // namespace internal |
| |
| // On Windows, by default, empty-base class optimization does not work, |
| // which means even if the base class is empty struct, it still consumes one |
| // byte for its body. __declspec(empty_bases) enables the optimization. |
| // cf) |
| // https://blogs.msdn.microsoft.com/vcblog/2016/03/30/optimizing-the-layout-of-empty-base-classes-in-vs2015-update-2-3/ |
| #ifdef OS_WIN |
| #define OPTIONAL_DECLSPEC_EMPTY_BASES __declspec(empty_bases) |
| #else |
| #define OPTIONAL_DECLSPEC_EMPTY_BASES |
| #endif |
| |
| // pdfium::Optional is a PDFium version of the C++17 optional class: |
| // std::optional documentation: |
| // http://en.cppreference.com/w/cpp/utility/optional |
| // Chromium documentation: |
| // https://chromium.googlesource.com/chromium/src/+/master/docs/optional.md |
| // |
| // These are the differences between the specification and the implementation: |
| // - Constructors do not use 'constexpr' as it is a C++14 extension. |
| // - 'constexpr' might be missing in some places for reasons specified locally. |
| // - No exceptions are thrown, because they are banned from PDFium. |
| // Marked noexcept for only move constructor and move assign operators. |
| // - All the non-members are in the 'pdfium' namespace instead of 'std'. |
| // |
| // Note that T cannot have a constructor T(Optional<T>) etc. Optional<T> checks |
| // T's constructor (specifically via IsConvertibleFromOptional), and in the |
| // check whether T can be constructible from Optional<T>, which is recursive |
| // so it does not work. As of Feb 2018, std::optional C++17 implementation in |
| // both clang and gcc has same limitation. MSVC SFINAE looks to have different |
| // behavior, but anyway it reports an error, too. |
| template <typename T> |
| class OPTIONAL_DECLSPEC_EMPTY_BASES Optional |
| : public internal::OptionalBase<T>, |
| public internal::CopyConstructible<std::is_copy_constructible<T>::value>, |
| public internal::MoveConstructible<std::is_move_constructible<T>::value>, |
| public internal::CopyAssignable<std::is_copy_constructible<T>::value && |
| std::is_copy_assignable<T>::value>, |
| public internal::MoveAssignable<std::is_move_constructible<T>::value && |
| std::is_move_assignable<T>::value> { |
| private: |
| // Disable some versions of T that are ill-formed. |
| // See: https://timsong-cpp.github.io/cppwp/n4659/optional#syn-1 |
| static_assert( |
| !std::is_same<internal::RemoveCvRefT<T>, in_place_t>::value, |
| "instantiation of pdfium::Optional with in_place_t is ill-formed"); |
| static_assert( |
| !std::is_same<internal::RemoveCvRefT<T>, nullopt_t>::value, |
| "instantiation of pdfium::Optional with nullopt_t is ill-formed"); |
| static_assert( |
| !std::is_reference<T>::value, |
| "instantiation of pdfium::Optional with a reference type is ill-formed"); |
| // See: https://timsong-cpp.github.io/cppwp/n4659/optional#optional-3 |
| static_assert( |
| std::is_destructible<T>::value, |
| "instantiation of pdfium::Optional with a non-destructible type " |
| "is ill-formed"); |
| // Arrays are explicitly disallowed because for arrays of known bound |
| // is_destructible is of undefined value. |
| // See: https://en.cppreference.com/w/cpp/types/is_destructible |
| static_assert( |
| !std::is_array<T>::value, |
| "instantiation of pdfium::Optional with an array type is ill-formed"); |
| |
| public: |
| #undef OPTIONAL_DECLSPEC_EMPTY_BASES |
| using value_type = T; |
| |
| // Defer default/copy/move constructor implementation to OptionalBase. |
| constexpr Optional() = default; |
| constexpr Optional(const Optional& other) = default; |
| constexpr Optional(Optional&& other) noexcept( |
| std::is_nothrow_move_constructible<T>::value) = default; |
| |
| constexpr Optional(nullopt_t) {} // NOLINT(runtime/explicit) |
| |
| // Converting copy constructor. "explicit" only if |
| // std::is_convertible<const U&, T>::value is false. It is implemented by |
| // declaring two almost same constructors, but that condition in enable_if_t |
| // is different, so that either one is chosen, thanks to SFINAE. |
| template < |
| typename U, |
| std::enable_if_t<std::is_constructible<T, const U&>::value && |
| !internal::IsConvertibleFromOptional<T, U>::value && |
| std::is_convertible<const U&, T>::value, |
| bool> = false> |
| Optional(const Optional<U>& other) : internal::OptionalBase<T>(other) {} |
| |
| template < |
| typename U, |
| std::enable_if_t<std::is_constructible<T, const U&>::value && |
| !internal::IsConvertibleFromOptional<T, U>::value && |
| !std::is_convertible<const U&, T>::value, |
| bool> = false> |
| explicit Optional(const Optional<U>& other) |
| : internal::OptionalBase<T>(other) {} |
| |
| // Converting move constructor. Similar to converting copy constructor, |
| // declaring two (explicit and non-explicit) constructors. |
| template < |
| typename U, |
| std::enable_if_t<std::is_constructible<T, U&&>::value && |
| !internal::IsConvertibleFromOptional<T, U>::value && |
| std::is_convertible<U&&, T>::value, |
| bool> = false> |
| Optional(Optional<U>&& other) : internal::OptionalBase<T>(std::move(other)) {} |
| |
| template < |
| typename U, |
| std::enable_if_t<std::is_constructible<T, U&&>::value && |
| !internal::IsConvertibleFromOptional<T, U>::value && |
| !std::is_convertible<U&&, T>::value, |
| bool> = false> |
| explicit Optional(Optional<U>&& other) |
| : internal::OptionalBase<T>(std::move(other)) {} |
| |
| template <class... Args> |
| constexpr explicit Optional(in_place_t, Args&&... args) |
| : internal::OptionalBase<T>(in_place, std::forward<Args>(args)...) {} |
| |
| template < |
| class U, |
| class... Args, |
| class = std::enable_if_t<std::is_constructible<value_type, |
| std::initializer_list<U>&, |
| Args...>::value>> |
| constexpr explicit Optional(in_place_t, |
| std::initializer_list<U> il, |
| Args&&... args) |
| : internal::OptionalBase<T>(in_place, il, std::forward<Args>(args)...) {} |
| |
| // Forward value constructor. Similar to converting constructors, |
| // conditionally explicit. |
| template < |
| typename U = value_type, |
| std::enable_if_t< |
| std::is_constructible<T, U&&>::value && |
| !std::is_same<internal::RemoveCvRefT<U>, in_place_t>::value && |
| !std::is_same<internal::RemoveCvRefT<U>, Optional<T>>::value && |
| std::is_convertible<U&&, T>::value, |
| bool> = false> |
| constexpr Optional(U&& value) |
| : internal::OptionalBase<T>(in_place, std::forward<U>(value)) {} |
| |
| template < |
| typename U = value_type, |
| std::enable_if_t< |
| std::is_constructible<T, U&&>::value && |
| !std::is_same<internal::RemoveCvRefT<U>, in_place_t>::value && |
| !std::is_same<internal::RemoveCvRefT<U>, Optional<T>>::value && |
| !std::is_convertible<U&&, T>::value, |
| bool> = false> |
| constexpr explicit Optional(U&& value) |
| : internal::OptionalBase<T>(in_place, std::forward<U>(value)) {} |
| |
| ~Optional() = default; |
| |
| // Defer copy-/move- assign operator implementation to OptionalBase. |
| Optional& operator=(const Optional& other) = default; |
| Optional& operator=(Optional&& other) noexcept( |
| std::is_nothrow_move_assignable<T>::value&& |
| std::is_nothrow_move_constructible<T>::value) = default; |
| |
| Optional& operator=(nullopt_t) { |
| FreeIfNeeded(); |
| return *this; |
| } |
| |
| // Perfect-forwarded assignment. |
| template <typename U> |
| std::enable_if_t< |
| !std::is_same<internal::RemoveCvRefT<U>, Optional<T>>::value && |
| std::is_constructible<T, U>::value && |
| std::is_assignable<T&, U>::value && |
| (!std::is_scalar<T>::value || |
| !std::is_same<std::decay_t<U>, T>::value), |
| Optional&> |
| operator=(U&& value) { |
| InitOrAssign(std::forward<U>(value)); |
| return *this; |
| } |
| |
| // Copy assign the state of other. |
| template <typename U> |
| std::enable_if_t<!internal::IsAssignableFromOptional<T, U>::value && |
| std::is_constructible<T, const U&>::value && |
| std::is_assignable<T&, const U&>::value, |
| Optional&> |
| operator=(const Optional<U>& other) { |
| CopyAssign(other); |
| return *this; |
| } |
| |
| // Move assign the state of other. |
| template <typename U> |
| std::enable_if_t<!internal::IsAssignableFromOptional<T, U>::value && |
| std::is_constructible<T, U>::value && |
| std::is_assignable<T&, U>::value, |
| Optional&> |
| operator=(Optional<U>&& other) { |
| MoveAssign(std::move(other)); |
| return *this; |
| } |
| |
| constexpr const T* operator->() const { |
| CHECK(storage_.is_populated_); |
| return &storage_.value_; |
| } |
| |
| constexpr T* operator->() { |
| CHECK(storage_.is_populated_); |
| return &storage_.value_; |
| } |
| |
| constexpr const T& operator*() const & { |
| CHECK(storage_.is_populated_); |
| return storage_.value_; |
| } |
| |
| constexpr T& operator*() & { |
| CHECK(storage_.is_populated_); |
| return storage_.value_; |
| } |
| |
| constexpr const T&& operator*() const && { |
| CHECK(storage_.is_populated_); |
| return std::move(storage_.value_); |
| } |
| |
| constexpr T&& operator*() && { |
| CHECK(storage_.is_populated_); |
| return std::move(storage_.value_); |
| } |
| |
| constexpr explicit operator bool() const { return storage_.is_populated_; } |
| |
| constexpr bool has_value() const { return storage_.is_populated_; } |
| |
| constexpr T& value() & { |
| CHECK(storage_.is_populated_); |
| return storage_.value_; |
| } |
| |
| constexpr const T& value() const & { |
| CHECK(storage_.is_populated_); |
| return storage_.value_; |
| } |
| |
| constexpr T&& value() && { |
| CHECK(storage_.is_populated_); |
| return std::move(storage_.value_); |
| } |
| |
| constexpr const T&& value() const && { |
| CHECK(storage_.is_populated_); |
| return std::move(storage_.value_); |
| } |
| |
| template <class U> |
| constexpr T value_or(U&& default_value) const& { |
| // TODO(mlamouri): add the following assert when possible: |
| // static_assert(std::is_copy_constructible<T>::value, |
| // "T must be copy constructible"); |
| static_assert(std::is_convertible<U, T>::value, |
| "U must be convertible to T"); |
| return storage_.is_populated_ |
| ? storage_.value_ |
| : static_cast<T>(std::forward<U>(default_value)); |
| } |
| |
| template <class U> |
| constexpr T value_or(U&& default_value) && { |
| // TODO(mlamouri): add the following assert when possible: |
| // static_assert(std::is_move_constructible<T>::value, |
| // "T must be move constructible"); |
| static_assert(std::is_convertible<U, T>::value, |
| "U must be convertible to T"); |
| return storage_.is_populated_ |
| ? std::move(storage_.value_) |
| : static_cast<T>(std::forward<U>(default_value)); |
| } |
| |
| void swap(Optional& other) { |
| if (!storage_.is_populated_ && !other.storage_.is_populated_) |
| return; |
| |
| if (storage_.is_populated_ != other.storage_.is_populated_) { |
| if (storage_.is_populated_) { |
| other.storage_.Init(std::move(storage_.value_)); |
| FreeIfNeeded(); |
| } else { |
| storage_.Init(std::move(other.storage_.value_)); |
| other.FreeIfNeeded(); |
| } |
| return; |
| } |
| |
| DCHECK(storage_.is_populated_ && other.storage_.is_populated_); |
| using std::swap; |
| swap(**this, *other); |
| } |
| |
| void reset() { FreeIfNeeded(); } |
| |
| template <class... Args> |
| T& emplace(Args&&... args) { |
| FreeIfNeeded(); |
| storage_.Init(std::forward<Args>(args)...); |
| return storage_.value_; |
| } |
| |
| template <class U, class... Args> |
| std::enable_if_t< |
| std::is_constructible<T, std::initializer_list<U>&, Args&&...>::value, |
| T&> |
| emplace(std::initializer_list<U> il, Args&&... args) { |
| FreeIfNeeded(); |
| storage_.Init(il, std::forward<Args>(args)...); |
| return storage_.value_; |
| } |
| |
| private: |
| // Accessing template base class's protected member needs explicit |
| // declaration to do so. |
| using internal::OptionalBase<T>::CopyAssign; |
| using internal::OptionalBase<T>::FreeIfNeeded; |
| using internal::OptionalBase<T>::InitOrAssign; |
| using internal::OptionalBase<T>::MoveAssign; |
| using internal::OptionalBase<T>::storage_; |
| }; |
| |
| // Here after defines comparation operators. The definition follows |
| // http://en.cppreference.com/w/cpp/utility/optional/operator_cmp |
| // while bool() casting is replaced by has_value() to meet the chromium |
| // style guide. |
| template <class T, class U> |
| constexpr bool operator==(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (lhs.has_value() != rhs.has_value()) |
| return false; |
| if (!lhs.has_value()) |
| return true; |
| return *lhs == *rhs; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator!=(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (lhs.has_value() != rhs.has_value()) |
| return true; |
| if (!lhs.has_value()) |
| return false; |
| return *lhs != *rhs; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (!rhs.has_value()) |
| return false; |
| if (!lhs.has_value()) |
| return true; |
| return *lhs < *rhs; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<=(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (!lhs.has_value()) |
| return true; |
| if (!rhs.has_value()) |
| return false; |
| return *lhs <= *rhs; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (!lhs.has_value()) |
| return false; |
| if (!rhs.has_value()) |
| return true; |
| return *lhs > *rhs; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>=(const Optional<T>& lhs, const Optional<U>& rhs) { |
| if (!rhs.has_value()) |
| return true; |
| if (!lhs.has_value()) |
| return false; |
| return *lhs >= *rhs; |
| } |
| |
| template <class T> |
| constexpr bool operator==(const Optional<T>& opt, nullopt_t) { |
| return !opt; |
| } |
| |
| template <class T> |
| constexpr bool operator==(nullopt_t, const Optional<T>& opt) { |
| return !opt; |
| } |
| |
| template <class T> |
| constexpr bool operator!=(const Optional<T>& opt, nullopt_t) { |
| return opt.has_value(); |
| } |
| |
| template <class T> |
| constexpr bool operator!=(nullopt_t, const Optional<T>& opt) { |
| return opt.has_value(); |
| } |
| |
| template <class T> |
| constexpr bool operator<(const Optional<T>& opt, nullopt_t) { |
| return false; |
| } |
| |
| template <class T> |
| constexpr bool operator<(nullopt_t, const Optional<T>& opt) { |
| return opt.has_value(); |
| } |
| |
| template <class T> |
| constexpr bool operator<=(const Optional<T>& opt, nullopt_t) { |
| return !opt; |
| } |
| |
| template <class T> |
| constexpr bool operator<=(nullopt_t, const Optional<T>& opt) { |
| return true; |
| } |
| |
| template <class T> |
| constexpr bool operator>(const Optional<T>& opt, nullopt_t) { |
| return opt.has_value(); |
| } |
| |
| template <class T> |
| constexpr bool operator>(nullopt_t, const Optional<T>& opt) { |
| return false; |
| } |
| |
| template <class T> |
| constexpr bool operator>=(const Optional<T>& opt, nullopt_t) { |
| return true; |
| } |
| |
| template <class T> |
| constexpr bool operator>=(nullopt_t, const Optional<T>& opt) { |
| return !opt; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator==(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt == value : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator==(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value == *opt : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator!=(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt != value : true; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator!=(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value != *opt : true; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt < value : true; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value < *opt : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<=(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt <= value : true; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator<=(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value <= *opt : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt > value : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value > *opt : true; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>=(const Optional<T>& opt, const U& value) { |
| return opt.has_value() ? *opt >= value : false; |
| } |
| |
| template <class T, class U> |
| constexpr bool operator>=(const U& value, const Optional<T>& opt) { |
| return opt.has_value() ? value >= *opt : true; |
| } |
| |
| template <class T> |
| constexpr Optional<std::decay_t<T>> make_optional(T&& value) { |
| return Optional<std::decay_t<T>>(std::forward<T>(value)); |
| } |
| |
| template <class T, class... Args> |
| constexpr Optional<T> make_optional(Args&&... args) { |
| return Optional<T>(in_place, std::forward<Args>(args)...); |
| } |
| |
| template <class T, class U, class... Args> |
| constexpr Optional<T> make_optional(std::initializer_list<U> il, |
| Args&&... args) { |
| return Optional<T>(in_place, il, std::forward<Args>(args)...); |
| } |
| |
| // Partial specialization for a function template is not allowed. Also, it is |
| // not allowed to add overload function to std namespace, while it is allowed |
| // to specialize the template in std. Thus, swap() (kind of) overloading is |
| // defined in pdfium namespace, instead. |
| template <class T> |
| std::enable_if_t<std::is_move_constructible<T>::value && |
| internal::IsSwappable<T>::value> |
| swap(Optional<T>& lhs, Optional<T>& rhs) { |
| lhs.swap(rhs); |
| } |
| |
| } // namespace pdfium |
| |
| namespace std { |
| |
| template <class T> |
| struct hash<pdfium::Optional<T>> { |
| size_t operator()(const pdfium::Optional<T>& opt) const { |
| return opt == pdfium::nullopt ? 0 : std::hash<T>()(*opt); |
| } |
| }; |
| |
| } // namespace std |
| |
| template <class T> |
| using Optional = pdfium::Optional<T>; |
| |
| #endif // THIRD_PARTY_BASE_OPTIONAL_H_ |