1 : // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : // Scopers help you manage ownership of a pointer, helping you easily manage the
6 : // a pointer within a scope, and automatically destroying the pointer at the
7 : // end of a scope. There are two main classes you will use, which coorespond
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 owernship, 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 :
39 : // This is an implementation designed to match the anticipated future TR2
40 : // implementation of the scoped_ptr class, and its closely-related brethren,
41 : // scoped_array, scoped_ptr_malloc.
42 :
43 : #include <assert.h>
44 : #include <stdlib.h>
45 : #include <cstddef>
46 :
47 : // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
48 : // automatically deletes the pointer it holds (if any).
49 : // That is, scoped_ptr<T> owns the T object that it points to.
50 : // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
51 : // Also like T*, scoped_ptr<T> is thread-compatible, and once you
52 : // dereference it, you get the threadsafety guarantees of T.
53 : //
54 : // The size of a scoped_ptr is small:
55 : // sizeof(scoped_ptr<C>) == sizeof(C*)
56 : template <class C>
57 : class scoped_ptr {
58 : public:
59 :
60 : // The element type
61 : typedef C element_type;
62 :
63 : // Constructor. Defaults to intializing with NULL.
64 : // There is no way to create an uninitialized scoped_ptr.
65 : // The input parameter must be allocated with new.
66 1424 : explicit scoped_ptr(C* p = NULL) : ptr_(p) { }
67 :
68 : // Destructor. If there is a C object, delete it.
69 : // We don't need to test ptr_ == NULL because C++ does that for us.
70 1420 : ~scoped_ptr() {
71 : enum { type_must_be_complete = sizeof(C) };
72 1420 : delete ptr_;
73 1420 : }
74 :
75 : // Reset. Deletes the current owned object, if any.
76 : // Then takes ownership of a new object, if given.
77 : // this->reset(this->get()) works.
78 1 : void reset(C* p = NULL) {
79 1 : if (p != ptr_) {
80 : enum { type_must_be_complete = sizeof(C) };
81 1 : delete ptr_;
82 1 : ptr_ = p;
83 : }
84 1 : }
85 :
86 : // Accessors to get the owned object.
87 : // operator* and operator-> will assert() if there is no current object.
88 0 : C& operator*() const {
89 0 : assert(ptr_ != NULL);
90 0 : return *ptr_;
91 : }
92 1421 : C* operator->() const {
93 1421 : assert(ptr_ != NULL);
94 1421 : return ptr_;
95 : }
96 1423 : C* get() const { return ptr_; }
97 :
98 : // Comparison operators.
99 : // These return whether two scoped_ptr refer to the same object, not just to
100 : // two different but equal objects.
101 : bool operator==(C* p) const { return ptr_ == p; }
102 : bool operator!=(C* p) const { return ptr_ != p; }
103 :
104 : // Swap two scoped pointers.
105 : void swap(scoped_ptr& p2) {
106 : C* tmp = ptr_;
107 : ptr_ = p2.ptr_;
108 : p2.ptr_ = tmp;
109 : }
110 :
111 : // Release a pointer.
112 : // The return value is the current pointer held by this object.
113 : // If this object holds a NULL pointer, the return value is NULL.
114 : // After this operation, this object will hold a NULL pointer,
115 : // and will not own the object any more.
116 1420 : C* release() {
117 1420 : C* retVal = ptr_;
118 1420 : ptr_ = NULL;
119 1420 : return retVal;
120 : }
121 :
122 : private:
123 : C* ptr_;
124 :
125 : // Forbid comparison of scoped_ptr types. If C2 != C, it totally doesn't
126 : // make sense, and if C2 == C, it still doesn't make sense because you should
127 : // never have the same object owned by two different scoped_ptrs.
128 : template <class C2> bool operator==(scoped_ptr<C2> const& p2) const;
129 : template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const;
130 :
131 : // Disallow evil constructors
132 : scoped_ptr(const scoped_ptr&);
133 : void operator=(const scoped_ptr&);
134 : };
135 :
136 : // Free functions
137 : template <class C>
138 : void swap(scoped_ptr<C>& p1, scoped_ptr<C>& p2) {
139 : p1.swap(p2);
140 : }
141 :
142 : template <class C>
143 : bool operator==(C* p1, const scoped_ptr<C>& p2) {
144 : return p1 == p2.get();
145 : }
146 :
147 : template <class C>
148 : bool operator!=(C* p1, const scoped_ptr<C>& p2) {
149 : return p1 != p2.get();
150 : }
151 :
152 : // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate
153 : // with new [] and the destructor deletes objects with delete [].
154 : //
155 : // As with scoped_ptr<C>, a scoped_array<C> either points to an object
156 : // or is NULL. A scoped_array<C> owns the object that it points to.
157 : // scoped_array<T> is thread-compatible, and once you index into it,
158 : // the returned objects have only the threadsafety guarantees of T.
159 : //
160 : // Size: sizeof(scoped_array<C>) == sizeof(C*)
161 : template <class C>
162 : class scoped_array {
163 : public:
164 :
165 : // The element type
166 : typedef C element_type;
167 :
168 : // Constructor. Defaults to intializing with NULL.
169 : // There is no way to create an uninitialized scoped_array.
170 : // The input parameter must be allocated with new [].
171 0 : explicit scoped_array(C* p = NULL) : array_(p) { }
172 :
173 : // Destructor. If there is a C object, delete it.
174 : // We don't need to test ptr_ == NULL because C++ does that for us.
175 0 : ~scoped_array() {
176 : enum { type_must_be_complete = sizeof(C) };
177 0 : delete[] array_;
178 0 : }
179 :
180 : // Reset. Deletes the current owned object, if any.
181 : // Then takes ownership of a new object, if given.
182 : // this->reset(this->get()) works.
183 : void reset(C* p = NULL) {
184 : if (p != array_) {
185 : enum { type_must_be_complete = sizeof(C) };
186 : delete[] array_;
187 : array_ = p;
188 : }
189 : }
190 :
191 : // Get one element of the current object.
192 : // Will assert() if there is no current object, or index i is negative.
193 0 : C& operator[](std::ptrdiff_t i) const {
194 0 : assert(i >= 0);
195 0 : assert(array_ != NULL);
196 0 : return array_[i];
197 : }
198 :
199 : // Get a pointer to the zeroth element of the current object.
200 : // If there is no current object, return NULL.
201 0 : C* get() const {
202 0 : return array_;
203 : }
204 :
205 : // Comparison operators.
206 : // These return whether two scoped_array refer to the same object, not just to
207 : // two different but equal objects.
208 : bool operator==(C* p) const { return array_ == p; }
209 : bool operator!=(C* p) const { return array_ != p; }
210 :
211 : // Swap two scoped arrays.
212 : void swap(scoped_array& p2) {
213 : C* tmp = array_;
214 : array_ = p2.array_;
215 : p2.array_ = tmp;
216 : }
217 :
218 : // Release an array.
219 : // The return value is the current pointer held by this object.
220 : // If this object holds a NULL pointer, the return value is NULL.
221 : // After this operation, this object will hold a NULL pointer,
222 : // and will not own the object any more.
223 : C* release() {
224 : C* retVal = array_;
225 : array_ = NULL;
226 : return retVal;
227 : }
228 :
229 : private:
230 : C* array_;
231 :
232 : // Forbid comparison of different scoped_array types.
233 : template <class C2> bool operator==(scoped_array<C2> const& p2) const;
234 : template <class C2> bool operator!=(scoped_array<C2> const& p2) const;
235 :
236 : // Disallow evil constructors
237 : scoped_array(const scoped_array&);
238 : void operator=(const scoped_array&);
239 : };
240 :
241 : // Free functions
242 : template <class C>
243 : void swap(scoped_array<C>& p1, scoped_array<C>& p2) {
244 : p1.swap(p2);
245 : }
246 :
247 : template <class C>
248 : bool operator==(C* p1, const scoped_array<C>& p2) {
249 : return p1 == p2.get();
250 : }
251 :
252 : template <class C>
253 : bool operator!=(C* p1, const scoped_array<C>& p2) {
254 : return p1 != p2.get();
255 : }
256 :
257 : // This class wraps the c library function free() in a class that can be
258 : // passed as a template argument to scoped_ptr_malloc below.
259 : class ScopedPtrMallocFree {
260 : public:
261 : inline void operator()(void* x) const {
262 : free(x);
263 : }
264 : };
265 :
266 : // scoped_ptr_malloc<> is similar to scoped_ptr<>, but it accepts a
267 : // second template argument, the functor used to free the object.
268 :
269 : template<class C, class FreeProc = ScopedPtrMallocFree>
270 : class scoped_ptr_malloc {
271 : public:
272 :
273 : // The element type
274 : typedef C element_type;
275 :
276 : // Constructor. Defaults to intializing with NULL.
277 : // There is no way to create an uninitialized scoped_ptr.
278 : // The input parameter must be allocated with an allocator that matches the
279 : // Free functor. For the default Free functor, this is malloc, calloc, or
280 : // realloc.
281 0 : explicit scoped_ptr_malloc(C* p = NULL): ptr_(p) {}
282 :
283 : // Destructor. If there is a C object, call the Free functor.
284 0 : ~scoped_ptr_malloc() {
285 0 : free_(ptr_);
286 0 : }
287 :
288 : // Reset. Calls the Free functor on the current owned object, if any.
289 : // Then takes ownership of a new object, if given.
290 : // this->reset(this->get()) works.
291 0 : void reset(C* p = NULL) {
292 0 : if (ptr_ != p) {
293 0 : free_(ptr_);
294 0 : ptr_ = p;
295 : }
296 0 : }
297 :
298 : // Get the current object.
299 : // operator* and operator-> will cause an assert() failure if there is
300 : // no current object.
301 : C& operator*() const {
302 : assert(ptr_ != NULL);
303 : return *ptr_;
304 : }
305 :
306 : C* operator->() const {
307 : assert(ptr_ != NULL);
308 : return ptr_;
309 : }
310 :
311 0 : C* get() const {
312 0 : return ptr_;
313 : }
314 :
315 : // Comparison operators.
316 : // These return whether a scoped_ptr_malloc and a plain pointer refer
317 : // to the same object, not just to two different but equal objects.
318 : // For compatibility wwith the boost-derived implementation, these
319 : // take non-const arguments.
320 : bool operator==(C* p) const {
321 : return ptr_ == p;
322 : }
323 :
324 : bool operator!=(C* p) const {
325 : return ptr_ != p;
326 : }
327 :
328 : // Swap two scoped pointers.
329 : void swap(scoped_ptr_malloc & b) {
330 : C* tmp = b.ptr_;
331 : b.ptr_ = ptr_;
332 : ptr_ = tmp;
333 : }
334 :
335 : // Release a pointer.
336 : // The return value is the current pointer held by this object.
337 : // If this object holds a NULL pointer, the return value is NULL.
338 : // After this operation, this object will hold a NULL pointer,
339 : // and will not own the object any more.
340 : C* release() {
341 : C* tmp = ptr_;
342 : ptr_ = NULL;
343 : return tmp;
344 : }
345 :
346 : private:
347 : C* ptr_;
348 :
349 : // no reason to use these: each scoped_ptr_malloc should have its own object
350 : template <class C2, class GP>
351 : bool operator==(scoped_ptr_malloc<C2, GP> const& p) const;
352 : template <class C2, class GP>
353 : bool operator!=(scoped_ptr_malloc<C2, GP> const& p) const;
354 :
355 : static FreeProc const free_;
356 :
357 : // Disallow evil constructors
358 : scoped_ptr_malloc(const scoped_ptr_malloc&);
359 : void operator=(const scoped_ptr_malloc&);
360 : };
361 :
362 : template<class C, class FP>
363 2928 : FP const scoped_ptr_malloc<C, FP>::free_ = FP();
364 :
365 : template<class C, class FP> inline
366 : void swap(scoped_ptr_malloc<C, FP>& a, scoped_ptr_malloc<C, FP>& b) {
367 : a.swap(b);
368 : }
369 :
370 : template<class C, class FP> inline
371 : bool operator==(C* p, const scoped_ptr_malloc<C, FP>& b) {
372 : return p == b.get();
373 : }
374 :
375 : template<class C, class FP> inline
376 : bool operator!=(C* p, const scoped_ptr_malloc<C, FP>& b) {
377 : return p != b.get();
378 : }
379 :
380 : #endif // BASE_SCOPED_PTR_H_
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