126 lines
5.0 KiB
C++
126 lines
5.0 KiB
C++
/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
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*
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* This library is open source and may be redistributed and/or modified under
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* the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
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* (at your option) any later version. The full license is in LICENSE file
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* included with this distribution, and on the openscenegraph.org website.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* OpenSceneGraph Public License for more details.
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*/
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#ifndef OSG_OBSERVER_PTR
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#define OSG_OBSERVER_PTR
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#include <osg/Notify>
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#include <osg/ref_ptr>
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#include <osg/Observer>
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namespace osg {
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/** Smart pointer for observed objects, that automatically set pointers to them to null when they deleted.
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* To use the observer_ptr<> robustly in mulit-threaded applications it is recommend to access the pointer via
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* the lock() method that passes back a ref_ptr<> that safely takes a reference to the object to prevent deletion
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* during usage of the object. In certain conditions it may be safe to use the pointer directly without using lock(),
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* which will confer a perfomance advantage, the conditions are:
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* 1) The data structure is only accessed/deleted in single threaded/serial way.
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* 2) The data strucutre is guarenteed by high level management of data strucutures and threads which avoid
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* possible situations where the observer_ptr<>'s object may be deleted by one thread whilst being accessed
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* by another.
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* If you are in any doubt about whether it is safe to access the object safe then use
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* ref_ptr<> observer_ptr<>.lock() combination. */
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template<class T>
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class observer_ptr : public Observer
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{
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public:
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typedef T element_type;
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observer_ptr() :_ptr(0L) {}
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observer_ptr(T* t):_ptr(t) { if (_ptr) _ptr->addObserver(this); }
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observer_ptr(const observer_ptr& rp):Observer(), _ptr(rp._ptr) { if (_ptr) _ptr->addObserver(this); }
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~observer_ptr()
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{
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
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if (_ptr) _ptr->removeObserver(this);
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}
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inline observer_ptr& operator = (const observer_ptr& rp)
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{
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if (&rp==this) return *this;
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
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if (_ptr==rp._ptr) return *this;
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if (_ptr) _ptr->removeObserver(this);
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_ptr = rp._ptr;
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if (_ptr) _ptr->addObserver(this);
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return *this;
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}
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inline observer_ptr& operator = (T* ptr)
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{
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
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if (_ptr==ptr) return *this;
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if (_ptr) _ptr->removeObserver(this);
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_ptr = ptr;
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if (_ptr) _ptr->addObserver(this);
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return *this;
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}
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// robust thread safe access to pointer
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ref_ptr<T> lock() const
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{
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
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return ref_ptr<T>(_ptr);
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}
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// get the raw C pointer
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inline T* get() const { return _ptr; }
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// comparison operators for observer_ptr.
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inline bool operator == (const observer_ptr& rp) const { return (_ptr==rp._ptr); }
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inline bool operator != (const observer_ptr& rp) const { return (_ptr!=rp._ptr); }
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inline bool operator < (const observer_ptr& rp) const { return (_ptr<rp._ptr); }
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inline bool operator > (const observer_ptr& rp) const { return (_ptr>rp._ptr); }
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// comparison operator for const T*.
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inline bool operator == (const T* ptr) const { return (_ptr==ptr); }
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inline bool operator != (const T* ptr) const { return (_ptr!=ptr); }
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inline bool operator < (const T* ptr) const { return (_ptr<ptr); }
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inline bool operator > (const T* ptr) const { return (_ptr>ptr); }
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// convinience methods for operating on object, however, access to not automatically threadsafe
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// to make thread safe one should either ensure a high level that object will not be deleted
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// which operating on it, or by using the observer_ptr<>::lock() to get a ref_ptr<> that ensures the
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// objects stay alive throughout all access to it.
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inline T& operator*() const { return *_ptr; }
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inline T* operator->() const { return _ptr; }
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inline bool operator!() const { return _ptr==0L; }
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inline bool valid() const { return _ptr!=0L; }
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protected:
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virtual void objectDeleted(void* obj)
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{
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T* ref_obj = static_cast<T*>(obj);
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OpenThreads::ScopedLock<OpenThreads::Mutex> lock(*getObserverMutex());
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if (ref_obj->referenceCount() == 0) _ptr = 0;
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}
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T* _ptr;
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};
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}
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#endif
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