1 // Copyright (c) 2012 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.
5 #ifndef BASE_MEMORY_REF_COUNTED_H_
6 #define BASE_MEMORY_REF_COUNTED_H_
10 #include "base/atomic_ref_count.h"
11 #include "base/base_export.h"
12 #include "base/compiler_specific.h"
13 #include "base/threading/thread_collision_warner.h"
19 class BASE_EXPORT RefCountedBase {
21 bool HasOneRef() const { return ref_count_ == 1; }
29 // Returns true if the object should self-delete.
33 mutable int ref_count_;
35 mutable bool in_dtor_;
38 DFAKE_MUTEX(add_release_);
40 DISALLOW_COPY_AND_ASSIGN(RefCountedBase);
43 class BASE_EXPORT RefCountedThreadSafeBase {
45 bool HasOneRef() const;
48 RefCountedThreadSafeBase();
49 ~RefCountedThreadSafeBase();
53 // Returns true if the object should self-delete.
57 mutable AtomicRefCount ref_count_;
59 mutable bool in_dtor_;
62 DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafeBase);
68 // A base class for reference counted classes. Otherwise, known as a cheap
69 // knock-off of WebKit's RefCounted<T> class. To use this guy just extend your
70 // class from it like so:
72 // class MyFoo : public base::RefCounted<MyFoo> {
75 // friend class base::RefCounted<MyFoo>;
79 // You should always make your destructor private, to avoid any code deleting
80 // the object accidently while there are references to it.
82 class RefCounted : public subtle::RefCountedBase {
87 subtle::RefCountedBase::AddRef();
90 void Release() const {
91 if (subtle::RefCountedBase::Release()) {
92 delete static_cast<const T*>(this);
100 DISALLOW_COPY_AND_ASSIGN(RefCounted<T>);
103 // Forward declaration.
104 template <class T, typename Traits> class RefCountedThreadSafe;
106 // Default traits for RefCountedThreadSafe<T>. Deletes the object when its ref
107 // count reaches 0. Overload to delete it on a different thread etc.
109 struct DefaultRefCountedThreadSafeTraits {
110 static void Destruct(const T* x) {
111 // Delete through RefCountedThreadSafe to make child classes only need to be
112 // friend with RefCountedThreadSafe instead of this struct, which is an
113 // implementation detail.
114 RefCountedThreadSafe<T,
115 DefaultRefCountedThreadSafeTraits>::DeleteInternal(x);
120 // A thread-safe variant of RefCounted<T>
122 // class MyFoo : public base::RefCountedThreadSafe<MyFoo> {
126 // If you're using the default trait, then you should add compile time
127 // asserts that no one else is deleting your object. i.e.
129 // friend class base::RefCountedThreadSafe<MyFoo>;
131 template <class T, typename Traits = DefaultRefCountedThreadSafeTraits<T> >
132 class RefCountedThreadSafe : public subtle::RefCountedThreadSafeBase {
134 RefCountedThreadSafe() {}
136 void AddRef() const {
137 subtle::RefCountedThreadSafeBase::AddRef();
140 void Release() const {
141 if (subtle::RefCountedThreadSafeBase::Release()) {
142 Traits::Destruct(static_cast<const T*>(this));
147 ~RefCountedThreadSafe() {}
150 friend struct DefaultRefCountedThreadSafeTraits<T>;
151 static void DeleteInternal(const T* x) { delete x; }
153 DISALLOW_COPY_AND_ASSIGN(RefCountedThreadSafe);
157 // A thread-safe wrapper for some piece of data so we can place other
158 // things in scoped_refptrs<>.
162 : public base::RefCountedThreadSafe< base::RefCountedData<T> > {
164 RefCountedData() : data() {}
165 RefCountedData(const T& in_value) : data(in_value) {}
170 friend class base::RefCountedThreadSafe<base::RefCountedData<T> >;
177 // A smart pointer class for reference counted objects. Use this class instead
178 // of calling AddRef and Release manually on a reference counted object to
179 // avoid common memory leaks caused by forgetting to Release an object
180 // reference. Sample usage:
182 // class MyFoo : public RefCounted<MyFoo> {
186 // void some_function() {
187 // scoped_refptr<MyFoo> foo = new MyFoo();
188 // foo->Method(param);
189 // // |foo| is released when this function returns
192 // void some_other_function() {
193 // scoped_refptr<MyFoo> foo = new MyFoo();
195 // foo = NULL; // explicitly releases |foo|
198 // foo->Method(param);
201 // The above examples show how scoped_refptr<T> acts like a pointer to T.
202 // Given two scoped_refptr<T> classes, it is also possible to exchange
203 // references between the two objects, like so:
206 // scoped_refptr<MyFoo> a = new MyFoo();
207 // scoped_refptr<MyFoo> b;
210 // // now, |b| references the MyFoo object, and |a| references NULL.
213 // To make both |a| and |b| in the above example reference the same MyFoo
214 // object, simply use the assignment operator:
217 // scoped_refptr<MyFoo> a = new MyFoo();
218 // scoped_refptr<MyFoo> b;
221 // // now, |a| and |b| each own a reference to the same MyFoo object.
225 class scoped_refptr {
227 typedef T element_type;
229 scoped_refptr() : ptr_(NULL) {
232 scoped_refptr(T* p) : ptr_(p) {
237 scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
242 template <typename U>
243 scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
253 T* get() const { return ptr_; }
255 // Allow scoped_refptr<C> to be used in boolean expression
256 // and comparison operations.
257 operator T*() const { return ptr_; }
259 T* operator->() const {
260 assert(ptr_ != NULL);
264 scoped_refptr<T>& operator=(T* p) {
265 // AddRef first so that self assignment should work
275 scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
276 return *this = r.ptr_;
279 template <typename U>
280 scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
281 return *this = r.get();
290 void swap(scoped_refptr<T>& r) {
298 // Handy utility for creating a scoped_refptr<T> out of a T* explicitly without
299 // having to retype all the template arguments
300 template <typename T>
301 scoped_refptr<T> make_scoped_refptr(T* t) {
302 return scoped_refptr<T>(t);
305 #endif // BASE_MEMORY_REF_COUNTED_H_