lyx_mirror/development/attic/cow_ptr.h

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// -*- C++ -*-
/**
* \file cow_ptr.h
* This file is part of LyX, the document processor.
* Licence details can be found in the file COPYING.
*
* \author Angus Leeming
*
* A pointer with copy-on-write semantics
*
* The original version of this class was written by Yonat Sharon
* and is freely available at http://ootips.org/yonat/
*
* I modified it to use boost::shared_ptr internally, rather than use his
* home-grown equivalent.
*/
#ifndef COW_PTR_H
#define COW_PTR_H
#include <boost/shared_ptr.hpp>
namespace lyx {
namespace support {
template <typename T>
class cow_ptr {
public:
explicit cow_ptr(T * = 0);
cow_ptr(cow_ptr const &);
cow_ptr & operator=(cow_ptr const &);
T const & operator*() const;
T const * operator->() const;
T const * get() const;
T & operator*();
T * operator->();
T * get();
private:
boost::shared_ptr<T> ptr_;
void copy();
};
template <typename T>
cow_ptr<T>::cow_ptr(T * p)
: ptr_(p)
{}
template <typename T>
cow_ptr<T>::cow_ptr(cow_ptr const & other)
: ptr_(other.ptr_)
{}
template <typename T>
cow_ptr<T> & cow_ptr<T>::operator=(cow_ptr const & other)
{
if (&other != this)
ptr_ = other.ptr_;
return *this;
}
template <typename T>
T const & cow_ptr<T>::operator*() const
{
return *ptr_;
}
template <typename T>
T const * cow_ptr<T>::operator->() const
{
return ptr_.get();
}
template <typename T>
T const * cow_ptr<T>::get() const
{
return ptr_.get();
}
template <typename T>
T & cow_ptr<T>::operator*()
{
copy();
return *ptr_;
}
template <typename T>
T * cow_ptr<T>::operator->()
{
copy();
return ptr_.get();
}
template <typename T>
T * cow_ptr<T>::get()
{
copy();
return ptr_.get();
}
template <typename T>
void cow_ptr<T>::copy()
{
if (!ptr_.unique())
ptr_ = boost::shared_ptr<T>(new T(*ptr_.get()));
}
} // namespace support
} // namespace lyx
#endif // NOT COW_PTR_H