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1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // Scopers help you manage ownership of a pointer, helping you easily manage the | 5 // Temporary fix due to third_party expectations. |
brettw
2011/03/24 20:37:30
Can you put a TODO here and list which third_part
| |
6 // a pointer within a scope, and automatically destroying the pointer at the | 6 #include "base/memory/scoped_ptr.h" |
7 // end of a scope. There are two main classes you will use, which correspond | |
8 // to the operators new/delete and new[]/delete[]. | |
9 // | |
10 // Example usage (scoped_ptr): | |
11 // { | |
12 // scoped_ptr<Foo> foo(new Foo("wee")); | |
13 // } // foo goes out of scope, releasing the pointer with it. | |
14 // | |
15 // { | |
16 // scoped_ptr<Foo> foo; // No pointer managed. | |
17 // foo.reset(new Foo("wee")); // Now a pointer is managed. | |
18 // foo.reset(new Foo("wee2")); // Foo("wee") was destroyed. | |
19 // foo.reset(new Foo("wee3")); // Foo("wee2") was destroyed. | |
20 // foo->Method(); // Foo::Method() called. | |
21 // foo.get()->Method(); // Foo::Method() called. | |
22 // SomeFunc(foo.release()); // SomeFunc takes ownership, foo no longer | |
23 // // manages a pointer. | |
24 // foo.reset(new Foo("wee4")); // foo manages a pointer again. | |
25 // foo.reset(); // Foo("wee4") destroyed, foo no longer | |
26 // // manages a pointer. | |
27 // } // foo wasn't managing a pointer, so nothing was destroyed. | |
28 // | |
29 // Example usage (scoped_array): | |
30 // { | |
31 // scoped_array<Foo> foo(new Foo[100]); | |
32 // foo.get()->Method(); // Foo::Method on the 0th element. | |
33 // foo[10].Method(); // Foo::Method on the 10th element. | |
34 // } | |
35 | |
36 #ifndef BASE_SCOPED_PTR_H_ | |
37 #define BASE_SCOPED_PTR_H_ | |
38 #pragma once | |
39 | |
40 // This is an implementation designed to match the anticipated future TR2 | |
41 // implementation of the scoped_ptr class, and its closely-related brethren, | |
42 // scoped_array, scoped_ptr_malloc. | |
43 | |
44 #include <assert.h> | |
45 #include <stddef.h> | |
46 #include <stdlib.h> | |
47 | |
48 #include "base/compiler_specific.h" | |
49 | |
50 // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T> | |
51 // automatically deletes the pointer it holds (if any). | |
52 // That is, scoped_ptr<T> owns the T object that it points to. | |
53 // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object. | |
54 // Also like T*, scoped_ptr<T> is thread-compatible, and once you | |
55 // dereference it, you get the threadsafety guarantees of T. | |
56 // | |
57 // The size of a scoped_ptr is small: | |
58 // sizeof(scoped_ptr<C>) == sizeof(C*) | |
59 template <class C> | |
60 class scoped_ptr { | |
61 public: | |
62 | |
63 // The element type | |
64 typedef C element_type; | |
65 | |
66 // Constructor. Defaults to initializing with NULL. | |
67 // There is no way to create an uninitialized scoped_ptr. | |
68 // The input parameter must be allocated with new. | |
69 explicit scoped_ptr(C* p = NULL) : ptr_(p) { } | |
70 | |
71 // Destructor. If there is a C object, delete it. | |
72 // We don't need to test ptr_ == NULL because C++ does that for us. | |
73 ~scoped_ptr() { | |
74 enum { type_must_be_complete = sizeof(C) }; | |
75 delete ptr_; | |
76 } | |
77 | |
78 // Reset. Deletes the current owned object, if any. | |
79 // Then takes ownership of a new object, if given. | |
80 // this->reset(this->get()) works. | |
81 void reset(C* p = NULL) { | |
82 if (p != ptr_) { | |
83 enum { type_must_be_complete = sizeof(C) }; | |
84 delete ptr_; | |
85 ptr_ = p; | |
86 } | |
87 } | |
88 | |
89 // Accessors to get the owned object. | |
90 // operator* and operator-> will assert() if there is no current object. | |
91 C& operator*() const { | |
92 assert(ptr_ != NULL); | |
93 return *ptr_; | |
94 } | |
95 C* operator->() const { | |
96 assert(ptr_ != NULL); | |
97 return ptr_; | |
98 } | |
99 C* get() const { return ptr_; } | |
100 | |
101 // Comparison operators. | |
102 // These return whether two scoped_ptr refer to the same object, not just to | |
103 // two different but equal objects. | |
104 bool operator==(C* p) const { return ptr_ == p; } | |
105 bool operator!=(C* p) const { return ptr_ != p; } | |
106 | |
107 // Swap two scoped pointers. | |
108 void swap(scoped_ptr& p2) { | |
109 C* tmp = ptr_; | |
110 ptr_ = p2.ptr_; | |
111 p2.ptr_ = tmp; | |
112 } | |
113 | |
114 // Release a pointer. | |
115 // The return value is the current pointer held by this object. | |
116 // If this object holds a NULL pointer, the return value is NULL. | |
117 // After this operation, this object will hold a NULL pointer, | |
118 // and will not own the object any more. | |
119 C* release() WARN_UNUSED_RESULT { | |
120 C* retVal = ptr_; | |
121 ptr_ = NULL; | |
122 return retVal; | |
123 } | |
124 | |
125 private: | |
126 C* ptr_; | |
127 | |
128 // Forbid comparison of scoped_ptr types. If C2 != C, it totally doesn't | |
129 // make sense, and if C2 == C, it still doesn't make sense because you should | |
130 // never have the same object owned by two different scoped_ptrs. | |
131 template <class C2> bool operator==(scoped_ptr<C2> const& p2) const; | |
132 template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const; | |
133 | |
134 // Disallow evil constructors | |
135 scoped_ptr(const scoped_ptr&); | |
136 void operator=(const scoped_ptr&); | |
137 }; | |
138 | |
139 // Free functions | |
140 template <class C> | |
141 void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) { | |
142 p1.swap(p2); | |
143 } | |
144 | |
145 template <class C> | |
146 bool operator==(C* p1, const scoped_ptr<C>& p2) { | |
147 return p1 == p2.get(); | |
148 } | |
149 | |
150 template <class C> | |
151 bool operator!=(C* p1, const scoped_ptr<C>& p2) { | |
152 return p1 != p2.get(); | |
153 } | |
154 | |
155 // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate | |
156 // with new [] and the destructor deletes objects with delete []. | |
157 // | |
158 // As with scoped_ptr<C>, a scoped_array<C> either points to an object | |
159 // or is NULL. A scoped_array<C> owns the object that it points to. | |
160 // scoped_array<T> is thread-compatible, and once you index into it, | |
161 // the returned objects have only the threadsafety guarantees of T. | |
162 // | |
163 // Size: sizeof(scoped_array<C>) == sizeof(C*) | |
164 template <class C> | |
165 class scoped_array { | |
166 public: | |
167 | |
168 // The element type | |
169 typedef C element_type; | |
170 | |
171 // Constructor. Defaults to intializing with NULL. | |
172 // There is no way to create an uninitialized scoped_array. | |
173 // The input parameter must be allocated with new []. | |
174 explicit scoped_array(C* p = NULL) : array_(p) { } | |
175 | |
176 // Destructor. If there is a C object, delete it. | |
177 // We don't need to test ptr_ == NULL because C++ does that for us. | |
178 ~scoped_array() { | |
179 enum { type_must_be_complete = sizeof(C) }; | |
180 delete[] array_; | |
181 } | |
182 | |
183 // Reset. Deletes the current owned object, if any. | |
184 // Then takes ownership of a new object, if given. | |
185 // this->reset(this->get()) works. | |
186 void reset(C* p = NULL) { | |
187 if (p != array_) { | |
188 enum { type_must_be_complete = sizeof(C) }; | |
189 delete[] array_; | |
190 array_ = p; | |
191 } | |
192 } | |
193 | |
194 // Get one element of the current object. | |
195 // Will assert() if there is no current object, or index i is negative. | |
196 C& operator[](ptrdiff_t i) const { | |
197 assert(i >= 0); | |
198 assert(array_ != NULL); | |
199 return array_[i]; | |
200 } | |
201 | |
202 // Get a pointer to the zeroth element of the current object. | |
203 // If there is no current object, return NULL. | |
204 C* get() const { | |
205 return array_; | |
206 } | |
207 | |
208 // Comparison operators. | |
209 // These return whether two scoped_array refer to the same object, not just to | |
210 // two different but equal objects. | |
211 bool operator==(C* p) const { return array_ == p; } | |
212 bool operator!=(C* p) const { return array_ != p; } | |
213 | |
214 // Swap two scoped arrays. | |
215 void swap(scoped_array& p2) { | |
216 C* tmp = array_; | |
217 array_ = p2.array_; | |
218 p2.array_ = tmp; | |
219 } | |
220 | |
221 // Release an array. | |
222 // The return value is the current pointer held by this object. | |
223 // If this object holds a NULL pointer, the return value is NULL. | |
224 // After this operation, this object will hold a NULL pointer, | |
225 // and will not own the object any more. | |
226 C* release() WARN_UNUSED_RESULT { | |
227 C* retVal = array_; | |
228 array_ = NULL; | |
229 return retVal; | |
230 } | |
231 | |
232 private: | |
233 C* array_; | |
234 | |
235 // Forbid comparison of different scoped_array types. | |
236 template <class C2> bool operator==(scoped_array<C2> const& p2) const; | |
237 template <class C2> bool operator!=(scoped_array<C2> const& p2) const; | |
238 | |
239 // Disallow evil constructors | |
240 scoped_array(const scoped_array&); | |
241 void operator=(const scoped_array&); | |
242 }; | |
243 | |
244 // Free functions | |
245 template <class C> | |
246 void swap(scoped_array<C>& p1, scoped_array<C>& p2) { | |
247 p1.swap(p2); | |
248 } | |
249 | |
250 template <class C> | |
251 bool operator==(C* p1, const scoped_array<C>& p2) { | |
252 return p1 == p2.get(); | |
253 } | |
254 | |
255 template <class C> | |
256 bool operator!=(C* p1, const scoped_array<C>& p2) { | |
257 return p1 != p2.get(); | |
258 } | |
259 | |
260 // This class wraps the c library function free() in a class that can be | |
261 // passed as a template argument to scoped_ptr_malloc below. | |
262 class ScopedPtrMallocFree { | |
263 public: | |
264 inline void operator()(void* x) const { | |
265 free(x); | |
266 } | |
267 }; | |
268 | |
269 // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a | |
270 // second template argument, the functor used to free the object. | |
271 | |
272 template<class C, class FreeProc = ScopedPtrMallocFree> | |
273 class scoped_ptr_malloc { | |
274 public: | |
275 | |
276 // The element type | |
277 typedef C element_type; | |
278 | |
279 // Constructor. Defaults to initializing with NULL. | |
280 // There is no way to create an uninitialized scoped_ptr. | |
281 // The input parameter must be allocated with an allocator that matches the | |
282 // Free functor. For the default Free functor, this is malloc, calloc, or | |
283 // realloc. | |
284 explicit scoped_ptr_malloc(C* p = NULL): ptr_(p) {} | |
285 | |
286 // Destructor. If there is a C object, call the Free functor. | |
287 ~scoped_ptr_malloc() { | |
288 free_(ptr_); | |
289 } | |
290 | |
291 // Reset. Calls the Free functor on the current owned object, if any. | |
292 // Then takes ownership of a new object, if given. | |
293 // this->reset(this->get()) works. | |
294 void reset(C* p = NULL) { | |
295 if (ptr_ != p) { | |
296 free_(ptr_); | |
297 ptr_ = p; | |
298 } | |
299 } | |
300 | |
301 // Get the current object. | |
302 // operator* and operator-> will cause an assert() failure if there is | |
303 // no current object. | |
304 C& operator*() const { | |
305 assert(ptr_ != NULL); | |
306 return *ptr_; | |
307 } | |
308 | |
309 C* operator->() const { | |
310 assert(ptr_ != NULL); | |
311 return ptr_; | |
312 } | |
313 | |
314 C* get() const { | |
315 return ptr_; | |
316 } | |
317 | |
318 // Comparison operators. | |
319 // These return whether a scoped_ptr_malloc and a plain pointer refer | |
320 // to the same object, not just to two different but equal objects. | |
321 // For compatibility with the boost-derived implementation, these | |
322 // take non-const arguments. | |
323 bool operator==(C* p) const { | |
324 return ptr_ == p; | |
325 } | |
326 | |
327 bool operator!=(C* p) const { | |
328 return ptr_ != p; | |
329 } | |
330 | |
331 // Swap two scoped pointers. | |
332 void swap(scoped_ptr_malloc & b) { | |
333 C* tmp = b.ptr_; | |
334 b.ptr_ = ptr_; | |
335 ptr_ = tmp; | |
336 } | |
337 | |
338 // Release a pointer. | |
339 // The return value is the current pointer held by this object. | |
340 // If this object holds a NULL pointer, the return value is NULL. | |
341 // After this operation, this object will hold a NULL pointer, | |
342 // and will not own the object any more. | |
343 C* release() WARN_UNUSED_RESULT { | |
344 C* tmp = ptr_; | |
345 ptr_ = NULL; | |
346 return tmp; | |
347 } | |
348 | |
349 private: | |
350 C* ptr_; | |
351 | |
352 // no reason to use these: each scoped_ptr_malloc should have its own object | |
353 template <class C2, class GP> | |
354 bool operator==(scoped_ptr_malloc<C2, GP> const& p) const; | |
355 template <class C2, class GP> | |
356 bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const; | |
357 | |
358 static FreeProc const free_; | |
359 | |
360 // Disallow evil constructors | |
361 scoped_ptr_malloc(const scoped_ptr_malloc&); | |
362 void operator=(const scoped_ptr_malloc&); | |
363 }; | |
364 | |
365 template<class C, class FP> | |
366 FP const scoped_ptr_malloc<C, FP>::free_ = FP(); | |
367 | |
368 template<class C, class FP> inline | |
369 void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) { | |
370 a.swap(b); | |
371 } | |
372 | |
373 template<class C, class FP> inline | |
374 bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) { | |
375 return p == b.get(); | |
376 } | |
377 | |
378 template<class C, class FP> inline | |
379 bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) { | |
380 return p != b.get(); | |
381 } | |
382 | |
383 #endif // BASE_SCOPED_PTR_H_ | |
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