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/*** |
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*auto_gcroot.h |
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* |
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* Copyright (c) Microsoft Corporation. All rights reserved. |
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* |
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*Purpose: automatic resource management, like std::auto_ptr which can be used |
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* to embed a virtual handle into a native type |
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* |
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* [Public] |
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* |
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****/ |
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#pragma once |
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#if !defined(_INC_MSCLR_AUTO_GCROOT) |
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#ifndef __cplusplus_cli |
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#error ERROR: msclr libraries are not compatible with /clr:oldSyntax |
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#endif |
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#include <vcclr.h> |
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#include <msclr\safebool.h> |
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#include <algorithm> |
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namespace msclr |
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{ |
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// Forward Declaration |
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template<typename _element_type> |
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class auto_gcroot; |
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namespace _detail |
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{ |
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// _auto_gcroot_ref is a proxy reference for auto_gcroot copying. |
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// auto_gcroot's copy constructor takes a non-const reference |
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// because it must assume ownership from the source. But this |
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// makes it impossible for auto_gcroot to be returned by value, |
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// because temporary objects cannot be bound to non-const |
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// references. Instead, a conversion to _auto_gcroot_ref is provided, |
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// and an auto_gcroot can be initialized from an _auto_gcroot_ref. |
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template<typename _element_type> |
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struct _auto_gcroot_ref |
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{ |
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// construct from compatible auto_gcroot |
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_auto_gcroot_ref( auto_gcroot<_element_type> & ref ) |
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: m_ref( ref ) |
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{ |
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} |
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// reference to constructor argument |
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auto_gcroot<_element_type> & m_ref; |
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}; |
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} // namespace detail |
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// wrap a resource to enforce strict ownership and ensure proper cleanup |
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template<typename _element_type> |
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class auto_gcroot |
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{ |
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private: |
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// disallow explicit comparisons to _safe_bool |
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bool operator==( _detail_class::_safe_bool ) const; |
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bool operator!=( _detail_class::_safe_bool ) const; |
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public: |
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// Constructors |
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// construct from object pointer |
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auto_gcroot( _element_type _ptr = nullptr ) |
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: m_ptr( _ptr ) |
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{ |
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} |
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// construct by assuming pointer from _right auto_gcroot |
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auto_gcroot( auto_gcroot<_element_type> & _right ) |
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: m_ptr( _right.release() ) |
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{ |
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} |
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// construct by assuming pointer from _right _detail::_auto_gcroot_ref |
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auto_gcroot( _detail::_auto_gcroot_ref<_element_type> _right ) |
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: m_ptr( _right.m_ref.release() ) |
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{ |
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} |
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template<typename _other_type> |
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auto_gcroot( auto_gcroot<_other_type> & _right ) |
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: m_ptr( _right.release() ) |
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{ |
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} |
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auto_gcroot<_element_type> & attach(_element_type _right) |
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{ |
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reset(_right); |
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return *this; |
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} |
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// assign compatible _right |
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auto_gcroot<_element_type> & attach( |
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auto_gcroot<_element_type> & _right ) |
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{ |
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reset( _right.release() ); |
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return *this; |
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} |
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// assign compatible _right.ref |
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auto_gcroot<_element_type> & attach( |
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_detail::_auto_gcroot_ref<_element_type> & _right ) |
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{ |
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reset( _right.m_ref.release() ); |
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return *this; |
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} |
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template<typename _other_type> |
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auto_gcroot<_element_type> & attach( |
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auto_gcroot<_other_type> & _right ) |
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{ |
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reset( _right.release() ); |
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return *this; |
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} |
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auto_gcroot<_element_type> & operator=(_element_type _right) |
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{ |
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// assign compatible _right.ref |
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auto_gcroot<_element_type> & operator=( |
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_detail::_auto_gcroot_ref<_element_type> & _right ) |
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{ |
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return attach(_right); |
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} |
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template<typename _other_type> |
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auto_gcroot<_element_type> & operator=( |
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auto_gcroot<_other_type> & _right ) |
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{ |
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return attach(_right); |
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} |
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_element_type get() const |
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{ |
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return m_ptr; |
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} |
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// return pointer to class object (assume pointer) |
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_element_type operator->() const |
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{ |
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return m_ptr; |
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} |
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// for use when auto_gcroot appears in a conditional |
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operator _detail_class::_safe_bool() const |
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{ |
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return valid() ? _detail_class::_safe_true : _detail_class::_safe_false; |
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} |
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// for use when auto_gcroot appears in a conditional |
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bool operator!() const |
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{ |
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return ! valid(); |
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} |
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// convert to compatible _detail::_auto_gcroot_ref |
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operator _detail::_auto_gcroot_ref<_element_type>() |
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{ |
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return _detail::_auto_gcroot_ref<_element_type>( *this ); |
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} |
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template<typename _other_type> |
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operator auto_gcroot<_other_type>() |
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{ |
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return auto_gcroot<_other_type>( *this ); |
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} |
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template<typename _other_type> |
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operator _detail::_auto_gcroot_ref<_other_type>() |
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{ |
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return _detail::_auto_gcroot_ref<_other_type>( *this ); |
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} |
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void swap( auto_gcroot<_element_type> & _right ) |
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{ |
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m_ptr.swap( _right.m_ptr ); |
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} |
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void reset( _element_type _new_ptr = nullptr ) |
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{ |
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if( _element_type(m_ptr) != _new_ptr ) |
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{ |
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if( valid() ) |
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{ |
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delete _element_type(m_ptr); |
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} |
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m_ptr = _new_ptr; |
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} |
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} |
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_element_type release() |
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{ |
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_element_type _tmp_ptr = m_ptr; |
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m_ptr = nullptr; |
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return _tmp_ptr; |
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} |
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// destroy the object |
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~auto_gcroot() |
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{ |
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if( valid() ) |
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{ |
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delete _element_type(m_ptr); |
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} |
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} |
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private: |
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bool valid() const |
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{ |
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// see if the managed resource is in the invalid state. |
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return _element_type(m_ptr) != nullptr; |
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} |
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// the wrapped object |
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gcroot<_element_type> m_ptr; |
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}; |
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// swap the contents of two auto_gcroot objects |
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template<typename _element_type> |
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void swap( auto_gcroot<_element_type> & _left, |
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auto_gcroot<_element_type> & _right ) |
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{ |
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_left.swap( _right ); |
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} |
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} // namespace msclr |
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#define _INC_MSCLR_AUTO_GCROOT |
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#endif // _INC_MSCLR_AUTO_GCROOT |
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