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99 lines
3.3 KiB
99 lines
3.3 KiB
/* |
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* Copyright (C) 2017 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 NETUTILS_STATUSOR_H |
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#define NETUTILS_STATUSOR_H |
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#include <cassert> |
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#include "netdutils/Status.h" |
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namespace android { |
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namespace netdutils { |
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// Wrapper around a combination of Status and application value type. |
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// T may be any copyable or movable type. |
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template <typename T> |
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class StatusOr { |
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public: |
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StatusOr() = default; |
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StatusOr(const Status status) : mStatus(status) { assert(!isOk(status)); } |
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StatusOr(const T& value) : mStatus(status::ok), mValue(value) {} |
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StatusOr(T&& value) : mStatus(status::ok), mValue(std::move(value)) {} |
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// Move constructor ok (if T supports move) |
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StatusOr(StatusOr&&) = default; |
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// Move assignment ok (if T supports move) |
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StatusOr& operator=(StatusOr&&) = default; |
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// Copy constructor ok (if T supports copy) |
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StatusOr(const StatusOr&) = default; |
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// Copy assignment ok (if T supports copy) |
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StatusOr& operator=(const StatusOr&) = default; |
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// Return const references to wrapped type |
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// It is an error to call value() when !isOk(status()) |
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const T& value() const & { return mValue; } |
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const T&& value() const && { return mValue; } |
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// Return rvalue references to wrapped type |
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// It is an error to call value() when !isOk(status()) |
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T& value() & { return mValue; } |
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T&& value() && { return mValue; } |
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// Return status assigned in constructor |
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const Status status() const { return mStatus; } |
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// Implict cast to Status |
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operator Status() const { return status(); } |
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private: |
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Status mStatus = status::undefined; |
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T mValue; |
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}; |
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template <typename T> |
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inline std::ostream& operator<<(std::ostream& os, const StatusOr<T>& s) { |
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return os << "StatusOr[status: " << s.status() << "]"; |
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} |
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#define ASSIGN_OR_RETURN_IMPL(tmp, lhs, stmt) \ |
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auto tmp = (stmt); \ |
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RETURN_IF_NOT_OK(tmp); \ |
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lhs = std::move(tmp.value()); |
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#define ASSIGN_OR_RETURN_CONCAT(line, lhs, stmt) \ |
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ASSIGN_OR_RETURN_IMPL(__CONCAT(_status_or_, line), lhs, stmt) |
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// Macro to allow exception-like handling of error return values. |
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// |
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// If the evaluation of stmt results in an error, return that error |
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// from the current function. Otherwise, assign the result to lhs. |
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// |
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// This macro supports both move and copy assignment operators. lhs |
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// may be either a new local variable or an existing non-const |
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// variable accessible in the current scope. |
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// |
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// Example usage: |
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// StatusOr<MyType> foo() { ... } |
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// |
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// ASSIGN_OR_RETURN(auto myVar, foo()); |
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// ASSIGN_OR_RETURN(myExistingVar, foo()); |
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// ASSIGN_OR_RETURN(myMemberVar, foo()); |
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#define ASSIGN_OR_RETURN(lhs, stmt) ASSIGN_OR_RETURN_CONCAT(__LINE__, lhs, stmt) |
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} // namespace netdutils |
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} // namespace android |
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#endif /* NETUTILS_STATUSOR_H */
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