/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_APEXD_STATUS_OR_H_
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#define ANDROID_APEXD_STATUS_OR_H_
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#include <string>
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#include <variant>
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#include <android-base/logging.h>
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#include <android-base/macros.h>
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#include "status.h"
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namespace android {
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namespace apex {
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template <typename T>
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class StatusOr {
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private:
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enum class StatusOrTag { kDummy };
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static constexpr std::in_place_index_t<0> kIndex0{};
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static constexpr std::in_place_index_t<1> kIndex1{};
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public:
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template <class... Args>
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explicit StatusOr(Args&&... args)
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: data_(kIndex1, std::forward<Args>(args)...) {}
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bool Ok() const WARN_UNUSED { return data_.index() != 0; }
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T& operator*() {
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CHECK(Ok());
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return *std::get_if<1u>(&data_);
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}
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T* operator->() {
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CHECK(Ok());
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return std::get_if<1u>(&data_);
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}
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const T* operator->() const {
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CHECK(Ok());
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return std::get_if<1u>(&data_);
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}
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const Status& ErrorStatus() const {
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CHECK(!Ok());
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const Status& status = *std::get_if<0u>(&data_);
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CHECK(!status.Ok());
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return status;
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}
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const std::string& ErrorMessage() const {
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return ErrorStatus().ErrorMessage();
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}
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static StatusOr MakeError(const std::string& msg) {
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return StatusOr(msg, StatusOrTag::kDummy);
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}
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static StatusOr MakeError(const Status& status) {
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return StatusOr(status.ErrorMessage(), StatusOrTag::kDummy);
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}
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// Added to be compatible with Status, i.e., T::Fail() works for both.
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static StatusOr Fail(const std::string& msg) {
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return StatusOr(msg, StatusOrTag::kDummy);
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}
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private:
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StatusOr(const std::string& msg, StatusOrTag dummy ATTRIBUTE_UNUSED)
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: data_(kIndex0, msg) {}
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std::variant<Status, T> data_;
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};
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} // namespace apex
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} // namespace android
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#endif // ANDROID_APEXD_STATUS_OR_H_
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