| // 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 Maybe_h |
| #define Maybe_h |
| |
| #include "platform/PlatformExport.h" |
| |
| namespace blink { |
| namespace protocol { |
| |
| class String16; |
| |
| template<typename T> |
| class Maybe { |
| public: |
| Maybe() { } |
| Maybe(PassOwnPtr<T> value) : m_value(std::move(value)) { } |
| void operator=(PassOwnPtr<T> value) { m_value = std::move(value); } |
| T* fromJust() const { ASSERT(m_value); return m_value.get(); } |
| T* fromMaybe(T* defaultValue) const { return m_value ? m_value.get() : defaultValue; } |
| bool isJust() const { return !!m_value; } |
| PassOwnPtr<T> takeJust() { ASSERT(m_value); return m_value.release(); } |
| private: |
| OwnPtr<T> m_value; |
| }; |
| |
| template<typename T> |
| class MaybeBase { |
| public: |
| MaybeBase() : m_isJust(false) { } |
| MaybeBase(T value) : m_isJust(true), m_value(value) { } |
| void operator=(T value) { m_value = value; m_isJust = true; } |
| T fromJust() const { ASSERT(m_isJust); return m_value; } |
| T fromMaybe(const T& defaultValue) const { return m_isJust ? m_value : defaultValue; } |
| bool isJust() const { return m_isJust; } |
| T takeJust() { ASSERT(m_isJust); return m_value; } |
| |
| protected: |
| bool m_isJust; |
| T m_value; |
| }; |
| |
| template<> |
| class Maybe<bool> : public MaybeBase<bool> { |
| public: |
| Maybe() { } |
| Maybe(bool value) : MaybeBase(value) { } |
| using MaybeBase::operator=; |
| }; |
| |
| template<> |
| class Maybe<int> : public MaybeBase<int> { |
| public: |
| Maybe() { } |
| Maybe(int value) : MaybeBase(value) { } |
| using MaybeBase::operator=; |
| }; |
| |
| template<> |
| class Maybe<double> : public MaybeBase<double> { |
| public: |
| Maybe() { } |
| Maybe(double value) : MaybeBase(value) { } |
| using MaybeBase::operator=; |
| }; |
| |
| template<> |
| class Maybe<String> : public MaybeBase<String> { |
| public: |
| Maybe() { } |
| Maybe(const String& value) : MaybeBase(value) { } |
| using MaybeBase::operator=; |
| }; |
| |
| template<> |
| class Maybe<String16> : public MaybeBase<String16> { |
| public: |
| Maybe() { } |
| Maybe(const String16& value) : MaybeBase(value) { } |
| using MaybeBase::operator=; |
| }; |
| |
| } // namespace platform |
| } // namespace blink |
| |
| #endif // !defined(Maybe_h) |