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| 1 | //===-- include/flang/Common/restorer.h -------------------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | // Utility: before overwriting a variable, capture its value and |
| 10 | // ensure that it will be restored when the Restorer goes out of scope. |
| 11 | // |
| 12 | // int x{3}; |
| 13 | // { |
| 14 | // auto save{common::ScopedSet(x, 4)}; |
| 15 | // // x is now 4 |
| 16 | // } |
| 17 | // // x is back to 3 |
| 18 | |
| 19 | #ifndef FORTRAN_COMMON_RESTORER_H_ |
| 20 | #define FORTRAN_COMMON_RESTORER_H_ |
| 21 | #include "idioms.h" |
| 22 | #include "flang/Common/api-attrs.h" |
| 23 | namespace Fortran::common { |
| 24 | template <typename A> class Restorer { |
| 25 | public: |
| 26 | explicit RT_API_ATTRS Restorer(A &p, A original) |
| 27 | : p_{p}, original_{std::move(original)} {} |
| 28 | RT_API_ATTRS ~Restorer() { p_ = std::move(original_); } |
| 29 | |
| 30 | // Inhibit any recreation of this restorer that would result in two restorers |
| 31 | // trying to restore the same reference. |
| 32 | Restorer(const Restorer &) = delete; |
| 33 | Restorer(Restorer &&that) = delete; |
| 34 | const Restorer &operator=(const Restorer &) = delete; |
| 35 | const Restorer &operator=(Restorer &&that) = delete; |
| 36 | |
| 37 | private: |
| 38 | A &p_; |
| 39 | A original_; |
| 40 | }; |
| 41 | |
| 42 | template <typename A, typename B> |
| 43 | RT_API_ATTRS common::IfNoLvalue<Restorer<A>, B> ScopedSet(A &to, B &&from) { |
| 44 | A original{std::move(to)}; |
| 45 | to = std::move(from); |
| 46 | return Restorer<A>{to, std::move(original)}; |
| 47 | } |
| 48 | template <typename A, typename B> |
| 49 | RT_API_ATTRS common::IfNoLvalue<Restorer<A>, B> ScopedSet( |
| 50 | A &to, const B &from) { |
| 51 | A original{std::move(to)}; |
| 52 | to = from; |
| 53 | return Restorer<A>{to, std::move(original)}; |
| 54 | } |
| 55 | } // namespace Fortran::common |
| 56 | #endif // FORTRAN_COMMON_RESTORER_H_ |
| 57 |
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