summaryrefslogtreecommitdiff
path: root/src/utils/cpp/expected.hpp
diff options
context:
space:
mode:
Diffstat (limited to 'src/utils/cpp/expected.hpp')
-rw-r--r--src/utils/cpp/expected.hpp80
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