mirror of
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145 lines
3.5 KiB
C++
145 lines
3.5 KiB
C++
/*
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* Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef SYSTEM_WRAPPERS_INTERFACE_SCOPED_REFPTR_H_
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#define SYSTEM_WRAPPERS_INTERFACE_SCOPED_REFPTR_H_
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#include <stddef.h>
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namespace webrtc {
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// Extracted from Chromium's src/base/memory/ref_counted.h.
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//
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// A smart pointer class for reference counted objects. Use this class instead
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// of calling AddRef and Release manually on a reference counted object to
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// avoid common memory leaks caused by forgetting to Release an object
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// reference. Sample usage:
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//
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// class MyFoo : public RefCounted<MyFoo> {
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// ...
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// };
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//
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// void some_function() {
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// scoped_refptr<MyFoo> foo = new MyFoo();
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// foo->Method(param);
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// // |foo| is released when this function returns
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// }
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//
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// void some_other_function() {
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// scoped_refptr<MyFoo> foo = new MyFoo();
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// ...
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// foo = NULL; // explicitly releases |foo|
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// ...
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// if (foo)
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// foo->Method(param);
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// }
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//
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// The above examples show how scoped_refptr<T> acts like a pointer to T.
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// Given two scoped_refptr<T> classes, it is also possible to exchange
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// references between the two objects, like so:
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//
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// {
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// scoped_refptr<MyFoo> a = new MyFoo();
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// scoped_refptr<MyFoo> b;
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//
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// b.swap(a);
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// // now, |b| references the MyFoo object, and |a| references NULL.
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// }
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//
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// To make both |a| and |b| in the above example reference the same MyFoo
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// object, simply use the assignment operator:
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//
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// {
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// scoped_refptr<MyFoo> a = new MyFoo();
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// scoped_refptr<MyFoo> b;
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//
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// b = a;
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// // now, |a| and |b| each own a reference to the same MyFoo object.
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// }
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//
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template <class T>
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class scoped_refptr {
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public:
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scoped_refptr() : ptr_(NULL) {
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}
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scoped_refptr(T* p) : ptr_(p) {
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if (ptr_)
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ptr_->AddRef();
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}
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scoped_refptr(const scoped_refptr<T>& r) : ptr_(r.ptr_) {
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if (ptr_)
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ptr_->AddRef();
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}
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template <typename U>
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scoped_refptr(const scoped_refptr<U>& r) : ptr_(r.get()) {
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if (ptr_)
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ptr_->AddRef();
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}
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~scoped_refptr() {
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if (ptr_)
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ptr_->Release();
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}
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T* get() const { return ptr_; }
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operator T*() const { return ptr_; }
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T* operator->() const { return ptr_; }
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// Release a pointer.
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// The return value is the current pointer held by this object.
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// If this object holds a NULL pointer, the return value is NULL.
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// After this operation, this object will hold a NULL pointer,
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// and will not own the object any more.
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T* release() {
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T* retVal = ptr_;
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ptr_ = NULL;
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return retVal;
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}
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scoped_refptr<T>& operator=(T* p) {
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// AddRef first so that self assignment should work
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if (p)
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p->AddRef();
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if (ptr_ )
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ptr_->Release();
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ptr_ = p;
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return *this;
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}
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scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
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return *this = r.ptr_;
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}
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template <typename U>
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scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
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return *this = r.get();
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}
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void swap(T** pp) {
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T* p = ptr_;
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ptr_ = *pp;
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*pp = p;
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}
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void swap(scoped_refptr<T>& r) {
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swap(&r.ptr_);
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}
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protected:
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T* ptr_;
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};
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} // namespace webrtc
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#endif // SYSTEM_WRAPPERS_INTERFACE_SCOPED_REFPTR_H_
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