1 | // |
2 | // SharedPtr.h |
3 | // |
4 | // Library: Foundation |
5 | // Package: Core |
6 | // Module: SharedPtr |
7 | // |
8 | // Definition of the SharedPtr template class. |
9 | // |
10 | // Copyright (c) 2005-2008, Applied Informatics Software Engineering GmbH. |
11 | // and Contributors. |
12 | // |
13 | // SPDX-License-Identifier: BSL-1.0 |
14 | // |
15 | |
16 | |
17 | #ifndef Foundation_SharedPtr_INCLUDED |
18 | #define Foundation_SharedPtr_INCLUDED |
19 | |
20 | |
21 | #include "Poco/Foundation.h" |
22 | #include "Poco/Exception.h" |
23 | #include "Poco/AtomicCounter.h" |
24 | #include <algorithm> |
25 | |
26 | |
27 | namespace Poco { |
28 | |
29 | |
30 | class ReferenceCounter |
31 | /// Simple ReferenceCounter object, does not delete itself when count reaches 0. |
32 | { |
33 | public: |
34 | ReferenceCounter(): _cnt(1) |
35 | { |
36 | } |
37 | |
38 | void duplicate() |
39 | { |
40 | ++_cnt; |
41 | } |
42 | |
43 | int release() |
44 | { |
45 | return --_cnt; |
46 | } |
47 | |
48 | int referenceCount() const |
49 | { |
50 | return _cnt.value(); |
51 | } |
52 | |
53 | private: |
54 | AtomicCounter _cnt; |
55 | }; |
56 | |
57 | |
58 | template <class C> |
59 | class ReleasePolicy |
60 | /// The default release policy for SharedPtr, which |
61 | /// simply uses the delete operator to delete an object. |
62 | { |
63 | public: |
64 | static void release(C* pObj) |
65 | /// Delete the object. |
66 | /// Note that pObj can be 0. |
67 | { |
68 | delete pObj; |
69 | } |
70 | }; |
71 | |
72 | |
73 | template <class C> |
74 | class ReleaseArrayPolicy |
75 | /// The release policy for SharedPtr holding arrays. |
76 | { |
77 | public: |
78 | static void release(C* pObj) |
79 | /// Delete the object. |
80 | /// Note that pObj can be 0. |
81 | { |
82 | delete [] pObj; |
83 | } |
84 | }; |
85 | |
86 | |
87 | template <class C, class RC = ReferenceCounter, class RP = ReleasePolicy<C> > |
88 | class SharedPtr |
89 | /// SharedPtr is a "smart" pointer for classes implementing |
90 | /// reference counting based garbage collection. |
91 | /// SharedPtr is thus similar to AutoPtr. Unlike the |
92 | /// AutoPtr template, which can only be used with |
93 | /// classes that support reference counting, SharedPtr |
94 | /// can be used with any class. For this to work, a |
95 | /// SharedPtr manages a reference count for the object |
96 | /// it manages. |
97 | /// |
98 | /// SharedPtr works in the following way: |
99 | /// If an SharedPtr is assigned an ordinary pointer to |
100 | /// an object (via the constructor or the assignment operator), |
101 | /// it takes ownership of the object and the object's reference |
102 | /// count is initialized to one. |
103 | /// If the SharedPtr is assigned another SharedPtr, the |
104 | /// object's reference count is incremented by one. |
105 | /// The destructor of SharedPtr decrements the object's |
106 | /// reference count by one and deletes the object if the |
107 | /// reference count reaches zero. |
108 | /// SharedPtr supports dereferencing with both the -> |
109 | /// and the * operator. An attempt to dereference a null |
110 | /// SharedPtr results in a NullPointerException being thrown. |
111 | /// SharedPtr also implements all relational operators and |
112 | /// a cast operator in case dynamic casting of the encapsulated data types |
113 | /// is required. |
114 | { |
115 | public: |
116 | SharedPtr(): _pCounter(new RC), _ptr(0) |
117 | { |
118 | } |
119 | |
120 | SharedPtr(C* ptr) |
121 | try: |
122 | _pCounter(new RC), |
123 | _ptr(ptr) |
124 | { |
125 | } |
126 | catch (...) |
127 | { |
128 | RP::release(ptr); |
129 | } |
130 | |
131 | template <class Other, class OtherRP> |
132 | SharedPtr(const SharedPtr<Other, RC, OtherRP>& ptr): _pCounter(ptr._pCounter), _ptr(const_cast<Other*>(ptr.get())) |
133 | { |
134 | _pCounter->duplicate(); |
135 | } |
136 | |
137 | SharedPtr(const SharedPtr& ptr): _pCounter(ptr._pCounter), _ptr(ptr._ptr) |
138 | { |
139 | _pCounter->duplicate(); |
140 | } |
141 | |
142 | ~SharedPtr() |
143 | { |
144 | try |
145 | { |
146 | release(); |
147 | } |
148 | catch (...) |
149 | { |
150 | poco_unexpected(); |
151 | } |
152 | } |
153 | |
154 | SharedPtr& assign(C* ptr) |
155 | { |
156 | if (get() != ptr) |
157 | { |
158 | SharedPtr tmp(ptr); |
159 | swap(tmp); |
160 | } |
161 | return *this; |
162 | } |
163 | |
164 | SharedPtr& assign(const SharedPtr& ptr) |
165 | { |
166 | if (&ptr != this) |
167 | { |
168 | SharedPtr tmp(ptr); |
169 | swap(tmp); |
170 | } |
171 | return *this; |
172 | } |
173 | |
174 | template <class Other, class OtherRP> |
175 | SharedPtr& assign(const SharedPtr<Other, RC, OtherRP>& ptr) |
176 | { |
177 | if (ptr.get() != _ptr) |
178 | { |
179 | SharedPtr tmp(ptr); |
180 | swap(tmp); |
181 | } |
182 | return *this; |
183 | } |
184 | |
185 | SharedPtr& operator = (C* ptr) |
186 | { |
187 | return assign(ptr); |
188 | } |
189 | |
190 | SharedPtr& operator = (const SharedPtr& ptr) |
191 | { |
192 | return assign(ptr); |
193 | } |
194 | |
195 | template <class Other, class OtherRP> |
196 | SharedPtr& operator = (const SharedPtr<Other, RC, OtherRP>& ptr) |
197 | { |
198 | return assign<Other>(ptr); |
199 | } |
200 | |
201 | void swap(SharedPtr& ptr) |
202 | { |
203 | std::swap(_ptr, ptr._ptr); |
204 | std::swap(_pCounter, ptr._pCounter); |
205 | } |
206 | |
207 | template <class Other> |
208 | SharedPtr<Other, RC, RP> cast() const |
209 | /// Casts the SharedPtr via a dynamic cast to the given type. |
210 | /// Returns an SharedPtr containing NULL if the cast fails. |
211 | /// Example: (assume class Sub: public Super) |
212 | /// SharedPtr<Super> super(new Sub()); |
213 | /// SharedPtr<Sub> sub = super.cast<Sub>(); |
214 | /// poco_assert (sub.get()); |
215 | { |
216 | Other* pOther = dynamic_cast<Other*>(_ptr); |
217 | if (pOther) |
218 | return SharedPtr<Other, RC, RP>(_pCounter, pOther); |
219 | return SharedPtr<Other, RC, RP>(); |
220 | } |
221 | |
222 | template <class Other> |
223 | SharedPtr<Other, RC, RP> unsafeCast() const |
224 | /// Casts the SharedPtr via a static cast to the given type. |
225 | /// Example: (assume class Sub: public Super) |
226 | /// SharedPtr<Super> super(new Sub()); |
227 | /// SharedPtr<Sub> sub = super.unsafeCast<Sub>(); |
228 | /// poco_assert (sub.get()); |
229 | { |
230 | Other* pOther = static_cast<Other*>(_ptr); |
231 | return SharedPtr<Other, RC, RP>(_pCounter, pOther); |
232 | } |
233 | |
234 | C* operator -> () |
235 | { |
236 | return deref(); |
237 | } |
238 | |
239 | const C* operator -> () const |
240 | { |
241 | return deref(); |
242 | } |
243 | |
244 | C& operator * () |
245 | { |
246 | return *deref(); |
247 | } |
248 | |
249 | const C& operator * () const |
250 | { |
251 | return *deref(); |
252 | } |
253 | |
254 | C* get() |
255 | { |
256 | return _ptr; |
257 | } |
258 | |
259 | const C* get() const |
260 | { |
261 | return _ptr; |
262 | } |
263 | |
264 | operator C* () |
265 | { |
266 | return _ptr; |
267 | } |
268 | |
269 | operator const C* () const |
270 | { |
271 | return _ptr; |
272 | } |
273 | |
274 | bool operator ! () const |
275 | { |
276 | return _ptr == 0; |
277 | } |
278 | |
279 | bool isNull() const |
280 | { |
281 | return _ptr == 0; |
282 | } |
283 | |
284 | bool operator == (const SharedPtr& ptr) const |
285 | { |
286 | return get() == ptr.get(); |
287 | } |
288 | |
289 | bool operator == (const C* ptr) const |
290 | { |
291 | return get() == ptr; |
292 | } |
293 | |
294 | bool operator == (C* ptr) const |
295 | { |
296 | return get() == ptr; |
297 | } |
298 | |
299 | bool operator != (const SharedPtr& ptr) const |
300 | { |
301 | return get() != ptr.get(); |
302 | } |
303 | |
304 | bool operator != (const C* ptr) const |
305 | { |
306 | return get() != ptr; |
307 | } |
308 | |
309 | bool operator != (C* ptr) const |
310 | { |
311 | return get() != ptr; |
312 | } |
313 | |
314 | bool operator < (const SharedPtr& ptr) const |
315 | { |
316 | return get() < ptr.get(); |
317 | } |
318 | |
319 | bool operator < (const C* ptr) const |
320 | { |
321 | return get() < ptr; |
322 | } |
323 | |
324 | bool operator < (C* ptr) const |
325 | { |
326 | return get() < ptr; |
327 | } |
328 | |
329 | bool operator <= (const SharedPtr& ptr) const |
330 | { |
331 | return get() <= ptr.get(); |
332 | } |
333 | |
334 | bool operator <= (const C* ptr) const |
335 | { |
336 | return get() <= ptr; |
337 | } |
338 | |
339 | bool operator <= (C* ptr) const |
340 | { |
341 | return get() <= ptr; |
342 | } |
343 | |
344 | bool operator > (const SharedPtr& ptr) const |
345 | { |
346 | return get() > ptr.get(); |
347 | } |
348 | |
349 | bool operator > (const C* ptr) const |
350 | { |
351 | return get() > ptr; |
352 | } |
353 | |
354 | bool operator > (C* ptr) const |
355 | { |
356 | return get() > ptr; |
357 | } |
358 | |
359 | bool operator >= (const SharedPtr& ptr) const |
360 | { |
361 | return get() >= ptr.get(); |
362 | } |
363 | |
364 | bool operator >= (const C* ptr) const |
365 | { |
366 | return get() >= ptr; |
367 | } |
368 | |
369 | bool operator >= (C* ptr) const |
370 | { |
371 | return get() >= ptr; |
372 | } |
373 | |
374 | int referenceCount() const |
375 | { |
376 | return _pCounter->referenceCount(); |
377 | } |
378 | |
379 | protected: |
380 | C* deref() const |
381 | { |
382 | if (!_ptr) |
383 | throw NullPointerException(); |
384 | |
385 | return _ptr; |
386 | } |
387 | |
388 | void release() |
389 | { |
390 | poco_assert_dbg (_pCounter); |
391 | int i = _pCounter->release(); |
392 | if (i == 0) |
393 | { |
394 | RP::release(_ptr); |
395 | _ptr = 0; |
396 | |
397 | delete _pCounter; |
398 | _pCounter = 0; |
399 | } |
400 | } |
401 | |
402 | SharedPtr(RC* pCounter, C* ptr): _pCounter(pCounter), _ptr(ptr) |
403 | /// for cast operation |
404 | { |
405 | poco_assert_dbg (_pCounter); |
406 | _pCounter->duplicate(); |
407 | } |
408 | |
409 | protected: |
410 | RC* _pCounter; |
411 | C* _ptr; |
412 | |
413 | template <class OtherC, class OtherRC, class OtherRP> friend class SharedPtr; |
414 | }; |
415 | |
416 | |
417 | template <class C, class RC, class RP> |
418 | inline void swap(SharedPtr<C, RC, RP>& p1, SharedPtr<C, RC, RP>& p2) |
419 | { |
420 | p1.swap(p2); |
421 | } |
422 | |
423 | |
424 | } // namespace Poco |
425 | |
426 | |
427 | #endif // Foundation_SharedPtr_INCLUDED |
428 | |