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Diffstat (limited to 'src/utils/cpp/expected.hpp')
-rw-r--r-- | src/utils/cpp/expected.hpp | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/src/utils/cpp/expected.hpp b/src/utils/cpp/expected.hpp new file mode 100644 index 00000000..823c4650 --- /dev/null +++ b/src/utils/cpp/expected.hpp @@ -0,0 +1,80 @@ +// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd. +// +// 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 +// +// http://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. + +#ifndef INCLUDED_SRC_UTILS_CPP_EXPECTED_HPP +#define INCLUDED_SRC_UTILS_CPP_EXPECTED_HPP + +#include <utility> +#include <variant> + +// TODO(modernize): replace this by std::unexpected once we switched to C++23 +template <class E> +class unexpected { + public: + explicit unexpected(E error) : error_{std::move(error)} {} + [[nodiscard]] auto error() && -> E { return std::move(error_); } + + private: + E error_; +}; + +// TODO(modernize): replace this by std::expected once we switched to C++23 +template <class T, class E> +class expected { + public: + expected(T value) noexcept // NOLINT + : value_{std::in_place_index<0>, std::move(value)} {} + expected(unexpected<E> unexpected) noexcept // NOLINT + : value_{std::in_place_index<1>, std::move(unexpected).error()} {} + + // Check whether the object contains an expected value + [[nodiscard]] auto has_value() const noexcept -> bool { + return value_.index() == 0; + } + [[nodiscard]] operator bool() const noexcept { // NOLINT + return has_value(); + } + + // Return the expected value + [[nodiscard]] auto value() const& -> T const& { + return std::get<0>(value_); + } + [[nodiscard]] auto value() && -> T { + return std::move(std::get<0>(value_)); + } + + // Access the expected value + [[nodiscard]] auto operator*() const& noexcept -> T const& { + return *std::get_if<0>(&value_); + } + [[nodiscard]] auto operator*() && noexcept -> T { + return std::move(*std::get_if<0>(&value_)); + } + [[nodiscard]] auto operator->() const noexcept -> T const* { + return std::get_if<0>(&value_); + } + + // Access the unexpected value + [[nodiscard]] auto error() const& noexcept -> const E& { + return *std::get_if<1>(&value_); + } + [[nodiscard]] auto error() && noexcept -> E { + return std::move(*std::get_if<1>(&value_)); + } + + private: + std::variant<T, E> value_; +}; + +#endif // INCLUDED_SRC_UTILS_CPP_EXPECTED_HPP |