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-rw-r--r-- | src/third-party/scnlib/include/scn/util/optional.h | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/src/third-party/scnlib/include/scn/util/optional.h b/src/third-party/scnlib/include/scn/util/optional.h new file mode 100644 index 0000000..9c0c808 --- /dev/null +++ b/src/third-party/scnlib/include/scn/util/optional.h @@ -0,0 +1,105 @@ +// Copyright 2017 Elias Kosunen +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// This file is a part of scnlib: +// https://github.com/eliaskosunen/scnlib + +#ifndef SCN_UTIL_OPTIONAL_H +#define SCN_UTIL_OPTIONAL_H + +#include "memory.h" + +namespace scn { + SCN_BEGIN_NAMESPACE + + struct nullopt_t { + }; + namespace { + static constexpr auto& nullopt = detail::static_const<nullopt_t>::value; + } + + /** + * A very lackluster optional implementation. + * Useful when scanning non-default-constructible types, especially with + * <tuple_return.h>: + * + * \code{.cpp} + * // implement scn::scanner for optional<mytype> + * optional<mytype> val; + * scn::scan(source, "{}", val); + * + * // with tuple_return: + * auto [result, val] = scn::scan_tuple<optional<mytype>>(source, "{}"); + * \endcode + */ + template <typename T> + class optional { + public: + using value_type = T; + using storage_type = detail::erased_storage<T>; + + optional() = default; + optional(nullopt_t) : m_storage{} {} + + optional(value_type val) : m_storage(SCN_MOVE(val)) {} + optional& operator=(value_type val) + { + m_storage = storage_type(SCN_MOVE(val)); + return *this; + } + + SCN_NODISCARD constexpr bool has_value() const noexcept + { + return m_storage.operator bool(); + } + constexpr explicit operator bool() const noexcept + { + return has_value(); + } + + SCN_CONSTEXPR14 T& get() noexcept + { + return m_storage.get(); + } + SCN_CONSTEXPR14 const T& get() const noexcept + { + return m_storage.get(); + } + + SCN_CONSTEXPR14 T& operator*() noexcept + { + return get(); + } + SCN_CONSTEXPR14 const T& operator*() const noexcept + { + return get(); + } + + SCN_CONSTEXPR14 T* operator->() noexcept + { + return m_storage.operator->(); + } + SCN_CONSTEXPR14 const T* operator->() const noexcept + { + return m_storage.operator->(); + } + + private: + storage_type m_storage; + }; + + SCN_END_NAMESPACE +} // namespace scn + +#endif |