| 1 | /* |
| 2 | * Copyright 2019-2020 (c) Philippe Proulx <pproulx@efficios.com> |
| 3 | * |
| 4 | * SPDX-License-Identifier: MIT |
| 5 | */ |
| 6 | |
| 7 | #ifndef BABELTRACE_CPP_COMMON_BT2_INTERNAL_BORROWED_OBJ_HPP |
| 8 | #define BABELTRACE_CPP_COMMON_BT2_INTERNAL_BORROWED_OBJ_HPP |
| 9 | |
| 10 | #include <functional> |
| 11 | #include <type_traits> |
| 12 | |
| 13 | #include "common/assert.h" |
| 14 | |
| 15 | namespace bt2 { |
| 16 | namespace internal { |
| 17 | |
| 18 | template <typename ObjT, typename LibObjT, typename RefFuncsT> |
| 19 | class SharedObj; |
| 20 | |
| 21 | /* |
| 22 | * An instance of this class wraps a pointer to a libbabeltrace2 object |
| 23 | * of type `LibObjT` without managing any reference counting. |
| 24 | * |
| 25 | * This is an abstract base class for any libbabeltrace2 object wrapper. |
| 26 | * |
| 27 | * `LibObjT` is the direct libbabeltrace2 object type, for example |
| 28 | * `bt_stream_class` or `const bt_value`. |
| 29 | * |
| 30 | * Methods of a derived class can call libObjPtr() to access the |
| 31 | * libbabeltrace2 object pointer. |
| 32 | */ |
| 33 | template <typename LibObjT> |
| 34 | class BorrowedObj |
| 35 | { |
| 36 | static_assert(!std::is_pointer<LibObjT>::value, "`LibObjT` must not be a pointer"); |
| 37 | |
| 38 | /* |
| 39 | * This makes it possible for a `BorrowedObj<const bt_something>` |
| 40 | * instance to get assigned an instance of |
| 41 | * `BorrowedObj<bt_something>` ("copy" constructor and "assignment" |
| 42 | * operator). |
| 43 | * |
| 44 | * C++ forbids the other way around. |
| 45 | */ |
| 46 | template <typename> |
| 47 | friend class BorrowedObj; |
| 48 | |
| 49 | protected: |
| 50 | /* libbabeltrace2 object pointer */ |
| 51 | using _LibObjPtr = LibObjT *; |
| 52 | |
| 53 | /* This complete borrowed object */ |
| 54 | using _ThisBorrowedObj = BorrowedObj<LibObjT>; |
| 55 | |
| 56 | /* |
| 57 | * Builds a borrowed object to wrap the libbabeltrace2 object |
| 58 | * pointer `libObjPtr`. |
| 59 | * |
| 60 | * `libObjPtr` must not be `nullptr`. |
| 61 | */ |
| 62 | explicit BorrowedObj(const _LibObjPtr libObjPtr) noexcept : _mLibObjPtr {libObjPtr} |
| 63 | { |
| 64 | BT_ASSERT(libObjPtr); |
| 65 | } |
| 66 | |
| 67 | /* Default copy operations */ |
| 68 | BorrowedObj(const BorrowedObj&) noexcept = default; |
| 69 | BorrowedObj& operator=(const BorrowedObj&) noexcept = default; |
| 70 | |
| 71 | /* |
| 72 | * Generic "copy" constructor. |
| 73 | * |
| 74 | * This converting constructor accepts both an instance of |
| 75 | * `_ThisBorrowedObj` and an instance (`other`) of |
| 76 | * `BorrowedObj<ConstLibObjT>`, where `ConstLibObjT` is the `const` |
| 77 | * version of `LibObjT`, if applicable. |
| 78 | * |
| 79 | * This makes it possible for a `BorrowedObj<const bt_something>` |
| 80 | * instance to be built from an instance of |
| 81 | * `BorrowedObj<bt_something>`. C++ forbids the other way around. |
| 82 | */ |
| 83 | template <typename OtherLibObjT> |
| 84 | BorrowedObj(const BorrowedObj<OtherLibObjT>& other) noexcept : BorrowedObj {other._mLibObjPtr} |
| 85 | { |
| 86 | } |
| 87 | |
| 88 | /* |
| 89 | * Generic "assignment" operator. |
| 90 | * |
| 91 | * This operator accepts both an instance of |
| 92 | * `_ThisBorrowedObj` and an instance (`other`) of |
| 93 | * `BorrowedObj<ConstLibObjT>`, where `ConstLibObjT` is the `const` |
| 94 | * version of `LibObjT`, if applicable. |
| 95 | * |
| 96 | * This makes it possible for a `BorrowedObj<const bt_something>` |
| 97 | * instance to get assigned an instance of |
| 98 | * `BorrowedObj<bt_something>`. C++ forbids the other way around. |
| 99 | */ |
| 100 | template <typename OtherLibObjT> |
| 101 | _ThisBorrowedObj& operator=(const BorrowedObj<OtherLibObjT>& other) noexcept |
| 102 | { |
| 103 | _mLibObjPtr = other._mLibObjPtr; |
| 104 | return *this; |
| 105 | } |
| 106 | |
| 107 | public: |
| 108 | /* |
| 109 | * Returns a hash of this object, solely based on its raw libbabeltrace2 |
| 110 | * pointer. |
| 111 | */ |
| 112 | std::size_t hash() const noexcept |
| 113 | { |
| 114 | return std::hash<_LibObjPtr> {}(_mLibObjPtr); |
| 115 | } |
| 116 | |
| 117 | /* |
| 118 | * Returns whether or not this object is the exact same as `other`, |
| 119 | * solely based on the raw libbabeltrace2 pointers. |
| 120 | */ |
| 121 | bool isSame(const _ThisBorrowedObj& other) const noexcept |
| 122 | { |
| 123 | return _mLibObjPtr == other._mLibObjPtr; |
| 124 | } |
| 125 | |
| 126 | /* Wrapped libbabeltrace2 object pointer */ |
| 127 | _LibObjPtr libObjPtr() const noexcept |
| 128 | { |
| 129 | return _mLibObjPtr; |
| 130 | } |
| 131 | |
| 132 | private: |
| 133 | _LibObjPtr _mLibObjPtr; |
| 134 | }; |
| 135 | |
| 136 | } /* namespace internal */ |
| 137 | } /* namespace bt2 */ |
| 138 | |
| 139 | #endif /* BABELTRACE_CPP_COMMON_BT2_INTERNAL_BORROWED_OBJ_HPP */ |