126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
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/*
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* Copyright 2004 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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/*
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* linked_ptr - simple reference linked pointer
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* (like reference counting, just using a linked list of the references
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* instead of their count.)
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*
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* The implementation stores three pointers for every linked_ptr, but
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* does not allocate anything on the free store.
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*/
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#ifndef WEBRTC_BASE_LINKED_PTR_H__
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#define WEBRTC_BASE_LINKED_PTR_H__
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namespace rtc {
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/* For ANSI-challenged compilers, you may want to #define
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* NO_MEMBER_TEMPLATES, explicit or mutable */
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#define NO_MEMBER_TEMPLATES
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template <class X> class linked_ptr
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{
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public:
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#ifndef NO_MEMBER_TEMPLATES
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# define TEMPLATE_FUNCTION template <class Y>
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TEMPLATE_FUNCTION friend class linked_ptr<Y>;
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#else
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# define TEMPLATE_FUNCTION
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typedef X Y;
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#endif
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typedef X element_type;
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explicit linked_ptr(X* p = 0) throw()
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: itsPtr(p) {itsPrev = itsNext = this;}
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~linked_ptr()
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{release();}
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linked_ptr(const linked_ptr& r) throw()
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{acquire(r);}
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linked_ptr& operator=(const linked_ptr& r)
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{
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if (this != &r) {
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release();
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acquire(r);
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}
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return *this;
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}
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#ifndef NO_MEMBER_TEMPLATES
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template <class Y> friend class linked_ptr<Y>;
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template <class Y> linked_ptr(const linked_ptr<Y>& r) throw()
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{acquire(r);}
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template <class Y> linked_ptr& operator=(const linked_ptr<Y>& r)
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{
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if (this != &r) {
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release();
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acquire(r);
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}
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return *this;
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}
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#endif // NO_MEMBER_TEMPLATES
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X& operator*() const throw() {return *itsPtr;}
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X* operator->() const throw() {return itsPtr;}
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X* get() const throw() {return itsPtr;}
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bool unique() const throw() {return itsPrev ? itsPrev==this : true;}
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private:
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X* itsPtr;
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mutable const linked_ptr* itsPrev;
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mutable const linked_ptr* itsNext;
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void acquire(const linked_ptr& r) throw()
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{ // insert this to the list
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itsPtr = r.itsPtr;
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itsNext = r.itsNext;
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itsNext->itsPrev = this;
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itsPrev = &r;
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#ifndef mutable
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r.itsNext = this;
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#else // for ANSI-challenged compilers
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(const_cast<linked_ptr<X>*>(&r))->itsNext = this;
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#endif
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}
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#ifndef NO_MEMBER_TEMPLATES
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template <class Y> void acquire(const linked_ptr<Y>& r) throw()
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{ // insert this to the list
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itsPtr = r.itsPtr;
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itsNext = r.itsNext;
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itsNext->itsPrev = this;
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itsPrev = &r;
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#ifndef mutable
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r.itsNext = this;
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#else // for ANSI-challenged compilers
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(const_cast<linked_ptr<X>*>(&r))->itsNext = this;
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#endif
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}
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#endif // NO_MEMBER_TEMPLATES
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void release()
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{ // erase this from the list, delete if unique
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if (unique()) delete itsPtr;
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else {
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itsPrev->itsNext = itsNext;
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itsNext->itsPrev = itsPrev;
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itsPrev = itsNext = 0;
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}
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itsPtr = 0;
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}
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};
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} // namespace rtc
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#endif // WEBRTC_BASE_LINKED_PTR_H__
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