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01bf7a3a PP |
1 | /* |
2 | * Copyright (c) 2019-2020 Philippe Proulx <pproulx@efficios.com> | |
3 | * | |
4 | * SPDX-License-Identifier: MIT | |
5 | */ | |
6 | ||
7f5cdaf0 PP |
7 | #ifndef BABELTRACE_CPP_COMMON_BT2_SHARED_OBJECT_HPP |
8 | #define BABELTRACE_CPP_COMMON_BT2_SHARED_OBJECT_HPP | |
01bf7a3a PP |
9 | |
10 | #include "common/assert.h" | |
11 | #include "cpp-common/optional.hpp" | |
12 | ||
13 | namespace bt2 { | |
01bf7a3a PP |
14 | |
15 | /* | |
16 | * An instance of this class wraps an optional instance of `ObjT` and | |
17 | * manages the reference counting of the underlying libbabeltrace2 | |
18 | * object. | |
19 | * | |
20 | * When you move a shared object, it becomes invalid, in that | |
21 | * operator*() and operator->() will either fail to assert in debug mode | |
22 | * or trigger a segmentation fault. | |
23 | * | |
24 | * `LibObjT` is the direct libbabeltrace2 object type, for example | |
25 | * `bt_stream_class` or `const bt_value`. | |
26 | * | |
27 | * RefFuncsT::get() must accept a `const LibObjT *` value and increment | |
28 | * its reference count. | |
29 | * | |
30 | * RefFuncsT::put() must accept a `const LibObjT *` value and decrement | |
31 | * its reference count. | |
32 | */ | |
33 | template <typename ObjT, typename LibObjT, typename RefFuncsT> | |
7f5cdaf0 | 34 | class SharedObject final |
01bf7a3a PP |
35 | { |
36 | /* | |
37 | * This makes it possible for a | |
7f5cdaf0 | 38 | * `SharedObject<Something, bt_something, ...>` instance to get |
01bf7a3a | 39 | * assigned an instance of |
7f5cdaf0 | 40 | * `SharedObject<SpecificSomething, bt_something, ...>` (copy/move |
e60a53f1 | 41 | * constructors and assignment operators), given that |
01bf7a3a PP |
42 | * `SpecificSomething` inherits `Something`. |
43 | */ | |
96643d28 | 44 | template <typename, typename, typename> |
7f5cdaf0 | 45 | friend class SharedObject; |
01bf7a3a | 46 | |
c9c0b6e2 PP |
47 | private: |
48 | /* | |
49 | * Builds a shared object from `obj` without getting a reference. | |
50 | */ | |
7f5cdaf0 | 51 | explicit SharedObject(const ObjT& obj) noexcept : _mObj {obj} |
c9c0b6e2 PP |
52 | { |
53 | } | |
54 | ||
e60a53f1 PP |
55 | /* |
56 | * Common generic "copy" constructor. | |
57 | * | |
58 | * This constructor is meant to be delegated to by the copy | |
59 | * constructor and the generic "copy" constructor. | |
60 | * | |
61 | * The second parameter, of type `int`, makes it possible to | |
62 | * delegate by deduction as you can't explicit the template | |
63 | * parameters when delegating to a constructor template. | |
64 | */ | |
65 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 | 66 | SharedObject(const SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>& other, int) noexcept : |
e60a53f1 PP |
67 | _mObj {other._mObj} |
68 | { | |
69 | this->_getRef(); | |
70 | } | |
71 | ||
72 | /* | |
73 | * Common generic "move" constructor. | |
74 | * | |
75 | * See the comment of the common generic "copy" constructor above. | |
76 | */ | |
77 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 | 78 | SharedObject(SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>&& other, int) noexcept : |
e60a53f1 PP |
79 | _mObj {other._mObj} |
80 | { | |
81 | /* Reset moved-from object */ | |
82 | other._reset(); | |
83 | } | |
84 | ||
01bf7a3a | 85 | public: |
c9c0b6e2 PP |
86 | /* |
87 | * Builds a shared object from `obj` without getting a reference. | |
88 | */ | |
7f5cdaf0 | 89 | static SharedObject createWithoutRef(const ObjT& obj) noexcept |
c9c0b6e2 | 90 | { |
7f5cdaf0 | 91 | return SharedObject {obj}; |
c9c0b6e2 | 92 | } |
01bf7a3a PP |
93 | |
94 | /* | |
c9c0b6e2 PP |
95 | * Builds a shared object from `libObjPtr` without getting a |
96 | * reference. | |
01bf7a3a | 97 | */ |
7f5cdaf0 | 98 | static SharedObject createWithoutRef(LibObjT * const libObjPtr) noexcept |
01bf7a3a | 99 | { |
7f5cdaf0 | 100 | return SharedObject::createWithoutRef(ObjT {libObjPtr}); |
01bf7a3a PP |
101 | } |
102 | ||
103 | /* | |
c9c0b6e2 PP |
104 | * Builds a shared object from `obj`, immediately getting a new |
105 | * reference. | |
01bf7a3a | 106 | */ |
7f5cdaf0 | 107 | static SharedObject createWithRef(const ObjT& obj) noexcept |
01bf7a3a | 108 | { |
7f5cdaf0 | 109 | SharedObject sharedObj {obj}; |
01bf7a3a PP |
110 | |
111 | sharedObj._getRef(); | |
112 | return sharedObj; | |
113 | } | |
114 | ||
c9c0b6e2 | 115 | /* |
7f5cdaf0 PP |
116 | * Builds a shared object from `libObjPtr`, immediately getting a |
117 | * new reference. | |
c9c0b6e2 | 118 | */ |
7f5cdaf0 | 119 | static SharedObject createWithRef(LibObjT * const libObjPtr) noexcept |
c9c0b6e2 | 120 | { |
7f5cdaf0 | 121 | return SharedObject::createWithRef(ObjT {libObjPtr}); |
c9c0b6e2 PP |
122 | } |
123 | ||
01bf7a3a | 124 | /* |
e60a53f1 PP |
125 | * Copy constructor. |
126 | */ | |
7f5cdaf0 | 127 | SharedObject(const SharedObject& other) noexcept : SharedObject {other, 0} |
e60a53f1 PP |
128 | { |
129 | } | |
130 | ||
131 | /* | |
132 | * Move constructor. | |
133 | */ | |
7f5cdaf0 | 134 | SharedObject(SharedObject&& other) noexcept : SharedObject {std::move(other), 0} |
e60a53f1 PP |
135 | { |
136 | } | |
137 | ||
138 | /* | |
139 | * Copy assignment operator. | |
140 | */ | |
7f5cdaf0 | 141 | SharedObject& operator=(const SharedObject& other) noexcept |
e60a53f1 PP |
142 | { |
143 | /* Use generic "copy" assignment operator */ | |
144 | return this->operator=<ObjT, LibObjT>(other); | |
145 | } | |
146 | ||
147 | /* | |
148 | * Move assignment operator. | |
149 | */ | |
7f5cdaf0 | 150 | SharedObject& operator=(SharedObject&& other) noexcept |
e60a53f1 PP |
151 | { |
152 | /* Use generic "move" assignment operator */ | |
153 | return this->operator=<ObjT, LibObjT>(std::move(other)); | |
154 | } | |
155 | ||
156 | /* | |
157 | * Generic "copy" constructor. | |
01bf7a3a | 158 | * |
7f5cdaf0 | 159 | * See the `friend class SharedObject` comment above. |
01bf7a3a PP |
160 | */ |
161 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 PP |
162 | SharedObject(const SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>& other) noexcept : |
163 | SharedObject {other, 0} | |
01bf7a3a | 164 | { |
01bf7a3a PP |
165 | } |
166 | ||
167 | /* | |
e60a53f1 | 168 | * Generic "move" constructor. |
01bf7a3a | 169 | * |
7f5cdaf0 | 170 | * See the `friend class SharedObject` comment above. |
01bf7a3a PP |
171 | */ |
172 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 PP |
173 | SharedObject(SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>&& other) noexcept : |
174 | SharedObject {std::move(other), 0} | |
01bf7a3a | 175 | { |
01bf7a3a PP |
176 | } |
177 | ||
178 | /* | |
e60a53f1 | 179 | * Generic "copy" assignment operator. |
01bf7a3a | 180 | * |
7f5cdaf0 | 181 | * See the `friend class SharedObject` comment above. |
01bf7a3a PP |
182 | */ |
183 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 | 184 | SharedObject& operator=(const SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>& other) noexcept |
01bf7a3a | 185 | { |
b5f55e9f | 186 | /* Put current object's reference */ |
01bf7a3a PP |
187 | this->_putRef(); |
188 | ||
b5f55e9f | 189 | /* Set new current object and get a reference */ |
01bf7a3a PP |
190 | _mObj = other._mObj; |
191 | this->_getRef(); | |
192 | ||
193 | return *this; | |
194 | } | |
195 | ||
196 | /* | |
e60a53f1 | 197 | * Generic "move" assignment operator. |
01bf7a3a | 198 | * |
7f5cdaf0 | 199 | * See the `friend class SharedObject` comment above. |
01bf7a3a PP |
200 | */ |
201 | template <typename OtherObjT, typename OtherLibObjT> | |
7f5cdaf0 | 202 | SharedObject& operator=(SharedObject<OtherObjT, OtherLibObjT, RefFuncsT>&& other) noexcept |
01bf7a3a | 203 | { |
b5f55e9f | 204 | /* Put current object's reference */ |
01bf7a3a PP |
205 | this->_putRef(); |
206 | ||
b5f55e9f | 207 | /* Set new current object */ |
01bf7a3a PP |
208 | _mObj = other._mObj; |
209 | ||
b5f55e9f | 210 | /* Reset moved-from object */ |
01bf7a3a PP |
211 | other._reset(); |
212 | ||
213 | return *this; | |
214 | } | |
215 | ||
7f5cdaf0 | 216 | ~SharedObject() |
01bf7a3a PP |
217 | { |
218 | this->_putRef(); | |
219 | } | |
220 | ||
221 | ObjT& operator*() noexcept | |
222 | { | |
223 | BT_ASSERT_DBG(_mObj); | |
224 | return *_mObj; | |
225 | } | |
226 | ||
227 | const ObjT& operator*() const noexcept | |
228 | { | |
229 | BT_ASSERT_DBG(_mObj); | |
230 | return *_mObj; | |
231 | } | |
232 | ||
233 | ObjT *operator->() noexcept | |
234 | { | |
235 | BT_ASSERT_DBG(_mObj); | |
236 | return &*_mObj; | |
237 | } | |
238 | ||
239 | const ObjT *operator->() const noexcept | |
240 | { | |
241 | BT_ASSERT_DBG(_mObj); | |
242 | return &*_mObj; | |
243 | } | |
244 | ||
d0b6533a SM |
245 | /* |
246 | * Transfers the reference of the object which this shared object | |
7f5cdaf0 PP |
247 | * wrapper manages and returns it, making the caller become an |
248 | * active owner. | |
d0b6533a SM |
249 | * |
250 | * This method makes this object invalid. | |
251 | */ | |
252 | ObjT release() noexcept | |
253 | { | |
254 | BT_ASSERT_DBG(_mObj); | |
255 | const auto obj = *_mObj; | |
256 | this->_reset(); | |
257 | return obj; | |
258 | } | |
259 | ||
01bf7a3a PP |
260 | private: |
261 | /* | |
262 | * Resets this shared object. | |
263 | * | |
264 | * To be used when moving it. | |
265 | */ | |
266 | void _reset() noexcept | |
267 | { | |
268 | _mObj.reset(); | |
269 | } | |
270 | ||
271 | /* | |
272 | * Gets a new reference using the configured libbabeltrace2 | |
273 | * reference incrementation function. | |
274 | */ | |
275 | void _getRef() const noexcept | |
276 | { | |
277 | if (_mObj) { | |
341a67c4 | 278 | RefFuncsT::get(_mObj->libObjPtr()); |
01bf7a3a PP |
279 | } |
280 | } | |
281 | ||
282 | /* | |
283 | * Puts a reference using the configured libbabeltrace2 reference | |
284 | * decrementation function. | |
285 | */ | |
286 | void _putRef() const noexcept | |
287 | { | |
288 | if (_mObj) { | |
341a67c4 | 289 | RefFuncsT::put(_mObj->libObjPtr()); |
01bf7a3a PP |
290 | } |
291 | } | |
292 | ||
293 | nonstd::optional<ObjT> _mObj; | |
294 | }; | |
295 | ||
b5f55e9f | 296 | } /* namespace bt2 */ |
01bf7a3a | 297 | |
7f5cdaf0 | 298 | #endif /* BABELTRACE_CPP_COMMON_BT2_SHARED_OBJECT_HPP */ |