1/*
2 *  Copyright 2011 The WebRTC Project Authors. All rights reserved.
3 *
4 *  Use of this source code is governed by a BSD-style license
5 *  that can be found in the LICENSE file in the root of the source
6 *  tree. An additional intellectual property rights grant can be found
7 *  in the file PATENTS.  All contributing project authors may
8 *  be found in the AUTHORS file in the root of the source tree.
9 */
10
11// Originally these classes are from Chromium.
12// http://src.chromium.org/viewvc/chrome/trunk/src/base/memory/ref_counted.h?view=markup
13
14//
15// A smart pointer class for reference counted objects.  Use this class instead
16// of calling AddRef and Release manually on a reference counted object to
17// avoid common memory leaks caused by forgetting to Release an object
18// reference.  Sample usage:
19//
20//   class MyFoo : public RefCounted<MyFoo> {
21//    ...
22//   };
23//
24//   void some_function() {
25//     scoped_refptr<MyFoo> foo = new MyFoo();
26//     foo->Method(param);
27//     // |foo| is released when this function returns
28//   }
29//
30//   void some_other_function() {
31//     scoped_refptr<MyFoo> foo = new MyFoo();
32//     ...
33//     foo = NULL;  // explicitly releases |foo|
34//     ...
35//     if (foo)
36//       foo->Method(param);
37//   }
38//
39// The above examples show how scoped_refptr<T> acts like a pointer to T.
40// Given two scoped_refptr<T> classes, it is also possible to exchange
41// references between the two objects, like so:
42//
43//   {
44//     scoped_refptr<MyFoo> a = new MyFoo();
45//     scoped_refptr<MyFoo> b;
46//
47//     b.swap(a);
48//     // now, |b| references the MyFoo object, and |a| references NULL.
49//   }
50//
51// To make both |a| and |b| in the above example reference the same MyFoo
52// object, simply use the assignment operator:
53//
54//   {
55//     scoped_refptr<MyFoo> a = new MyFoo();
56//     scoped_refptr<MyFoo> b;
57//
58//     b = a;
59//     // now, |a| and |b| each own a reference to the same MyFoo object.
60//   }
61//
62
63#ifndef WEBRTC_BASE_SCOPED_REF_PTR_H_
64#define WEBRTC_BASE_SCOPED_REF_PTR_H_
65
66#include <stddef.h>
67
68namespace rtc {
69
70template <class T>
71class scoped_refptr {
72 public:
73  scoped_refptr() : ptr_(NULL) {
74  }
75
76  scoped_refptr(T* p) : ptr_(p) {
77    if (ptr_)
78      ptr_->AddRef();
79  }
80
81  scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
82    if (ptr_)
83      ptr_->AddRef();
84  }
85
86  template <typename U>
87  scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
88    if (ptr_)
89      ptr_->AddRef();
90  }
91
92  ~scoped_refptr() {
93    if (ptr_)
94      ptr_->Release();
95  }
96
97  T* get() const { return ptr_; }
98  operator T*() const { return ptr_; }
99  T* operator->() const { return ptr_; }
100
101  // Release a pointer.
102  // The return value is the current pointer held by this object.
103  // If this object holds a NULL pointer, the return value is NULL.
104  // After this operation, this object will hold a NULL pointer,
105  // and will not own the object any more.
106  T* release() {
107    T* retVal = ptr_;
108    ptr_ = NULL;
109    return retVal;
110  }
111
112  scoped_refptr<T>& operator=(T* p) {
113    // AddRef first so that self assignment should work
114    if (p)
115      p->AddRef();
116    if (ptr_ )
117      ptr_ ->Release();
118    ptr_ = p;
119    return *this;
120  }
121
122  scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
123    return *this = r.ptr_;
124  }
125
126  template <typename U>
127  scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
128    return *this = r.get();
129  }
130
131  void swap(T** pp) {
132    T* p = ptr_;
133    ptr_ = *pp;
134    *pp = p;
135  }
136
137  void swap(scoped_refptr<T>& r) {
138    swap(&r.ptr_);
139  }
140
141 protected:
142  T* ptr_;
143};
144
145}  // namespace rtc
146
147#endif  // WEBRTC_BASE_SCOPED_REF_PTR_H_
148