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| 1 | //===-- include/flang/Common/reference-counted.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 | #ifndef FORTRAN_COMMON_REFERENCE_COUNTED_H_ |
| 10 | #define FORTRAN_COMMON_REFERENCE_COUNTED_H_ |
| 11 | |
| 12 | // A class template of smart pointers to objects with their own |
| 13 | // reference counting object lifetimes that's lighter weight |
| 14 | // than std::shared_ptr<>. Not thread-safe. |
| 15 | |
| 16 | namespace Fortran::common { |
| 17 | |
| 18 | // A base class for reference-counted objects. Must be public. |
| 19 | template <typename A> class ReferenceCounted { |
| 20 | public: |
| 21 | ReferenceCounted() {} |
| 22 | int references() const { return references_; } |
| 23 | void TakeReference() { ++references_; } |
| 24 | void DropReference() { |
| 25 | if (--references_ == 0) { |
| 26 | delete static_cast<A *>(this); |
| 27 | } |
| 28 | } |
| 29 | |
| 30 | private: |
| 31 | int references_{0}; |
| 32 | }; |
| 33 | |
| 34 | // A reference to a reference-counted object. |
| 35 | template <typename A> class CountedReference { |
| 36 | public: |
| 37 | using type = A; |
| 38 | CountedReference() {} |
| 39 | CountedReference(type *m) : p_{m} { Take(); } |
| 40 | CountedReference(const CountedReference &c) : p_{c.p_} { Take(); } |
| 41 | CountedReference(CountedReference &&c) : p_{c.p_} { c.p_ = nullptr; } |
| 42 | CountedReference &operator=(const CountedReference &c) { |
| 43 | c.Take(); |
| 44 | Drop(); |
| 45 | p_ = c.p_; |
| 46 | return *this; |
| 47 | } |
| 48 | CountedReference &operator=(CountedReference &&c) { |
| 49 | A *p{c.p_}; |
| 50 | c.p_ = nullptr; |
| 51 | Drop(); |
| 52 | p_ = p; |
| 53 | return *this; |
| 54 | } |
| 55 | ~CountedReference() { Drop(); } |
| 56 | operator bool() const { return p_ != nullptr; } |
| 57 | type *get() const { return p_; } |
| 58 | type &operator*() const { return *p_; } |
| 59 | type *operator->() const { return p_; } |
| 60 | |
| 61 | private: |
| 62 | void Take() const { |
| 63 | if (p_) { |
| 64 | p_->TakeReference(); |
| 65 | } |
| 66 | } |
| 67 | void Drop() { |
| 68 | if (p_) { |
| 69 | p_->DropReference(); |
| 70 | p_ = nullptr; |
| 71 | } |
| 72 | } |
| 73 | |
| 74 | type *p_{nullptr}; |
| 75 | }; |
| 76 | } // namespace Fortran::common |
| 77 | #endif // FORTRAN_COMMON_REFERENCE_COUNTED_H_ |
| 78 |
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