68 lines
2.9 KiB
C++
68 lines
2.9 KiB
C++
/*
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* Copyright 2011 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 API_REF_COUNT_H_
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#define API_REF_COUNT_H_
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namespace webrtc {
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// Refcounted objects should implement the following informal interface:
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//
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// void AddRef() const ;
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// RefCountReleaseStatus Release() const;
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//
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// You may access members of a reference-counted object, including the AddRef()
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// and Release() methods, only if you already own a reference to it, or if
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// you're borrowing someone else's reference. (A newly created object is a
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// special case: the reference count is zero on construction, and the code that
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// creates the object should immediately call AddRef(), bringing the reference
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// count from zero to one, e.g., by constructing an rtc::scoped_refptr).
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//
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// AddRef() creates a new reference to the object.
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//
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// Release() releases a reference to the object; the caller now has one less
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// reference than before the call. Returns kDroppedLastRef if the number of
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// references dropped to zero because of this (in which case the object destroys
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// itself). Otherwise, returns kOtherRefsRemained, to signal that at the precise
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// time the caller's reference was dropped, other references still remained (but
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// if other threads own references, this may of course have changed by the time
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// Release() returns).
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//
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// The caller of Release() must treat it in the same way as a delete operation:
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// Regardless of the return value from Release(), the caller mustn't access the
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// object. The object might still be alive, due to references held by other
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// users of the object, but the object can go away at any time, e.g., as the
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// result of another thread calling Release().
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//
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// Calling AddRef() and Release() manually is discouraged. It's recommended to
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// use rtc::scoped_refptr to manage all pointers to reference counted objects.
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// Note that rtc::scoped_refptr depends on compile-time duck-typing; formally
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// implementing the below RefCountInterface is not required.
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enum class RefCountReleaseStatus { kDroppedLastRef, kOtherRefsRemained };
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// Interfaces where refcounting is part of the public api should
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// inherit this abstract interface. The implementation of these
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// methods is usually provided by the RefCountedObject template class,
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// applied as a leaf in the inheritance tree.
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class RefCountInterface {
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public:
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virtual void AddRef() const = 0;
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virtual RefCountReleaseStatus Release() const = 0;
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// Non-public destructor, because Release() has exclusive responsibility for
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// destroying the object.
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protected:
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virtual ~RefCountInterface() {}
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};
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} // namespace webrtc
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#endif // API_REF_COUNT_H_
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