OLD | NEW |
| (Empty) |
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 | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef BASE_WIN_SCOPED_COMPTR_H_ | |
6 #define BASE_WIN_SCOPED_COMPTR_H_ | |
7 | |
8 #include <unknwn.h> | |
9 | |
10 #include "base/logging.h" | |
11 #include "base/memory/ref_counted.h" | |
12 | |
13 namespace base { | |
14 namespace win { | |
15 | |
16 // A fairly minimalistic smart class for COM interface pointers. | |
17 // Uses scoped_refptr for the basic smart pointer functionality | |
18 // and adds a few IUnknown specific services. | |
19 template <class Interface, const IID* interface_id = &__uuidof(Interface)> | |
20 class ScopedComPtr : public scoped_refptr<Interface> { | |
21 public: | |
22 // Utility template to prevent users of ScopedComPtr from calling AddRef | |
23 // and/or Release() without going through the ScopedComPtr class. | |
24 class BlockIUnknownMethods : public Interface { | |
25 private: | |
26 STDMETHOD(QueryInterface)(REFIID iid, void** object) = 0; | |
27 STDMETHOD_(ULONG, AddRef)() = 0; | |
28 STDMETHOD_(ULONG, Release)() = 0; | |
29 }; | |
30 | |
31 typedef scoped_refptr<Interface> ParentClass; | |
32 | |
33 ScopedComPtr() { | |
34 } | |
35 | |
36 explicit ScopedComPtr(Interface* p) : ParentClass(p) { | |
37 } | |
38 | |
39 ScopedComPtr(const ScopedComPtr<Interface, interface_id>& p) | |
40 : ParentClass(p) { | |
41 } | |
42 | |
43 ~ScopedComPtr() { | |
44 // We don't want the smart pointer class to be bigger than the pointer | |
45 // it wraps. | |
46 COMPILE_ASSERT(sizeof(ScopedComPtr<Interface, interface_id>) == | |
47 sizeof(Interface*), ScopedComPtrSize); | |
48 } | |
49 | |
50 // Explicit Release() of the held object. Useful for reuse of the | |
51 // ScopedComPtr instance. | |
52 // Note that this function equates to IUnknown::Release and should not | |
53 // be confused with e.g. scoped_ptr::release(). | |
54 void Release() { | |
55 if (ptr_ != NULL) { | |
56 ptr_->Release(); | |
57 ptr_ = NULL; | |
58 } | |
59 } | |
60 | |
61 // Sets the internal pointer to NULL and returns the held object without | |
62 // releasing the reference. | |
63 Interface* Detach() { | |
64 Interface* p = ptr_; | |
65 ptr_ = NULL; | |
66 return p; | |
67 } | |
68 | |
69 // Accepts an interface pointer that has already been addref-ed. | |
70 void Attach(Interface* p) { | |
71 DCHECK(!ptr_); | |
72 ptr_ = p; | |
73 } | |
74 | |
75 // Retrieves the pointer address. | |
76 // Used to receive object pointers as out arguments (and take ownership). | |
77 // The function DCHECKs on the current value being NULL. | |
78 // Usage: Foo(p.Receive()); | |
79 Interface** Receive() { | |
80 DCHECK(!ptr_) << "Object leak. Pointer must be NULL"; | |
81 return &ptr_; | |
82 } | |
83 | |
84 // A convenience for whenever a void pointer is needed as an out argument. | |
85 void** ReceiveVoid() { | |
86 return reinterpret_cast<void**>(Receive()); | |
87 } | |
88 | |
89 template <class Query> | |
90 HRESULT QueryInterface(Query** p) { | |
91 DCHECK(p != NULL); | |
92 DCHECK(ptr_ != NULL); | |
93 // IUnknown already has a template version of QueryInterface | |
94 // so the iid parameter is implicit here. The only thing this | |
95 // function adds are the DCHECKs. | |
96 return ptr_->QueryInterface(p); | |
97 } | |
98 | |
99 // QI for times when the IID is not associated with the type. | |
100 HRESULT QueryInterface(const IID& iid, void** obj) { | |
101 DCHECK(obj != NULL); | |
102 DCHECK(ptr_ != NULL); | |
103 return ptr_->QueryInterface(iid, obj); | |
104 } | |
105 | |
106 // Queries |other| for the interface this object wraps and returns the | |
107 // error code from the other->QueryInterface operation. | |
108 HRESULT QueryFrom(IUnknown* object) { | |
109 DCHECK(object != NULL); | |
110 return object->QueryInterface(Receive()); | |
111 } | |
112 | |
113 // Convenience wrapper around CoCreateInstance | |
114 HRESULT CreateInstance(const CLSID& clsid, IUnknown* outer = NULL, | |
115 DWORD context = CLSCTX_ALL) { | |
116 DCHECK(!ptr_); | |
117 HRESULT hr = ::CoCreateInstance(clsid, outer, context, *interface_id, | |
118 reinterpret_cast<void**>(&ptr_)); | |
119 return hr; | |
120 } | |
121 | |
122 // Checks if the identity of |other| and this object is the same. | |
123 bool IsSameObject(IUnknown* other) { | |
124 if (!other && !ptr_) | |
125 return true; | |
126 | |
127 if (!other || !ptr_) | |
128 return false; | |
129 | |
130 ScopedComPtr<IUnknown> my_identity; | |
131 QueryInterface(my_identity.Receive()); | |
132 | |
133 ScopedComPtr<IUnknown> other_identity; | |
134 other->QueryInterface(other_identity.Receive()); | |
135 | |
136 return my_identity == other_identity; | |
137 } | |
138 | |
139 // Provides direct access to the interface. | |
140 // Here we use a well known trick to make sure we block access to | |
141 // IUnknown methods so that something bad like this doesn't happen: | |
142 // ScopedComPtr<IUnknown> p(Foo()); | |
143 // p->Release(); | |
144 // ... later the destructor runs, which will Release() again. | |
145 // and to get the benefit of the DCHECKs we add to QueryInterface. | |
146 // There's still a way to call these methods if you absolutely must | |
147 // by statically casting the ScopedComPtr instance to the wrapped interface | |
148 // and then making the call... but generally that shouldn't be necessary. | |
149 BlockIUnknownMethods* operator->() const { | |
150 DCHECK(ptr_ != NULL); | |
151 return reinterpret_cast<BlockIUnknownMethods*>(ptr_); | |
152 } | |
153 | |
154 // Pull in operator=() from the parent class. | |
155 using scoped_refptr<Interface>::operator=; | |
156 | |
157 // static methods | |
158 | |
159 static const IID& iid() { | |
160 return *interface_id; | |
161 } | |
162 }; | |
163 | |
164 } // namespace win | |
165 } // namespace base | |
166 | |
167 #endif // BASE_WIN_SCOPED_COMPTR_H_ | |
OLD | NEW |