C++ 智能指针
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template<typename _Tp>
class auto_ptr
{
private:
_Tp* _M_ptr;
public:
/// The pointed-to type.
typedef _Tp element_type;
/**
* @brief An %auto_ptr is usually constructed from a raw pointer.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p.
*/
explicit
auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership.
*/
auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a
* pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership.
*/
template<typename _Tp1>
auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership. The object that this one @e
* used to own and track has been deleted.
*/
auto_ptr&
operator=(auto_ptr& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership. The object that this one @e
* used to own and track has been deleted.
*/
template<typename _Tp1>
auto_ptr&
operator=(auto_ptr<_Tp1>& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* When the %auto_ptr goes out of scope, the object it owns is
* deleted. If it no longer owns anything (i.e., @c get() is
* @c NULL), then this has no effect.
*
* @if maint
* The C++ standard says there is supposed to be an empty throw
* specification here, but omitting it is standard conforming. Its
* presence can be detected only if _Tp::~_Tp() throws, but this is
* prohibited. [17.4.3.6]/2
* @end maint
*/
~auto_ptr() { delete _M_ptr; }
/**
* @brief Smart pointer dereferencing.
*
* If this %auto_ptr no longer owns anything, then this
* operation will crash. (For a smart pointer, "no longer owns
* anything" is the same as being a null pointer, and you know
* what happens when you dereference one of those...)
*/
element_type&
operator*() const throw()
{
_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
return *_M_ptr;
}
/**
* @brief Smart pointer dereferencing.
*
* This returns the pointer itself, which the language then will
* automatically cause to be dereferenced.
*/
element_type*
operator->() const throw()
{
_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
return _M_ptr;
}
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts
* a raw pointer.
*
* @note This %auto_ptr still owns the memory.
*/
element_type*
get() const throw() { return _M_ptr; }
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts
* a raw pointer.
*
* @note This %auto_ptr no longer owns the memory. When this object
* goes out of scope, nothing will happen.
*/
element_type*
release() throw()
{
element_type* __tmp = _M_ptr;
_M_ptr = 0;
return __tmp;
}
/**
* @brief Forcibly deletes the managed object.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p. The
* previous object has been deleted.
*/
void
reset(element_type* __p = 0) throw()
{
if (__p != _M_ptr)
{
delete _M_ptr;
_M_ptr = __p;
}
}
/** @{
* @brief Automatic conversions
*
* These operations convert an %auto_ptr into and from an auto_ptr_ref
* automatically as needed. This allows constructs such as
* @code
* auto_ptr<Derived> func_returning_auto_ptr(.....);
* ...
* auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
* @endcode
*/
auto_ptr(auto_ptr_ref<element_type> __ref) throw()
: _M_ptr(__ref._M_ptr) { }
auto_ptr&
operator=(auto_ptr_ref<element_type> __ref) throw()
{
if (__ref._M_ptr != this->get())
{
delete _M_ptr;
_M_ptr = __ref._M_ptr;
}
return *this;
}
template<typename _Tp1>
operator auto_ptr_ref<_Tp1>() throw()
{ return auto_ptr_ref<_Tp1>(this->release()); }
template<typename _Tp1>
operator auto_ptr<_Tp1>() throw()
{ return auto_ptr<_Tp1>(this->release()); }
/** @} */
};
} // namespace std
class auto_ptr
{
private:
_Tp* _M_ptr;
public:
/// The pointed-to type.
typedef _Tp element_type;
/**
* @brief An %auto_ptr is usually constructed from a raw pointer.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p.
*/
explicit
auto_ptr(element_type* __p = 0) throw() : _M_ptr(__p) { }
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership.
*/
auto_ptr(auto_ptr& __a) throw() : _M_ptr(__a.release()) { }
/**
* @brief An %auto_ptr can be constructed from another %auto_ptr.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a
* pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership.
*/
template<typename _Tp1>
auto_ptr(auto_ptr<_Tp1>& __a) throw() : _M_ptr(__a.release()) { }
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of the same type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership. The object that this one @e
* used to own and track has been deleted.
*/
auto_ptr&
operator=(auto_ptr& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* @brief %auto_ptr assignment operator.
* @param a Another %auto_ptr of a different but related type.
*
* A pointer-to-Tp1 must be convertible to a pointer-to-Tp/element_type.
*
* This object now @e owns the object previously owned by @a a,
* which has given up ownsership. The object that this one @e
* used to own and track has been deleted.
*/
template<typename _Tp1>
auto_ptr&
operator=(auto_ptr<_Tp1>& __a) throw()
{
reset(__a.release());
return *this;
}
/**
* When the %auto_ptr goes out of scope, the object it owns is
* deleted. If it no longer owns anything (i.e., @c get() is
* @c NULL), then this has no effect.
*
* @if maint
* The C++ standard says there is supposed to be an empty throw
* specification here, but omitting it is standard conforming. Its
* presence can be detected only if _Tp::~_Tp() throws, but this is
* prohibited. [17.4.3.6]/2
* @end maint
*/
~auto_ptr() { delete _M_ptr; }
/**
* @brief Smart pointer dereferencing.
*
* If this %auto_ptr no longer owns anything, then this
* operation will crash. (For a smart pointer, "no longer owns
* anything" is the same as being a null pointer, and you know
* what happens when you dereference one of those...)
*/
element_type&
operator*() const throw()
{
_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
return *_M_ptr;
}
/**
* @brief Smart pointer dereferencing.
*
* This returns the pointer itself, which the language then will
* automatically cause to be dereferenced.
*/
element_type*
operator->() const throw()
{
_GLIBCXX_DEBUG_ASSERT(_M_ptr != 0);
return _M_ptr;
}
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts
* a raw pointer.
*
* @note This %auto_ptr still owns the memory.
*/
element_type*
get() const throw() { return _M_ptr; }
/**
* @brief Bypassing the smart pointer.
* @return The raw pointer being managed.
*
* You can get a copy of the pointer that this object owns, for
* situations such as passing to a function which only accepts
* a raw pointer.
*
* @note This %auto_ptr no longer owns the memory. When this object
* goes out of scope, nothing will happen.
*/
element_type*
release() throw()
{
element_type* __tmp = _M_ptr;
_M_ptr = 0;
return __tmp;
}
/**
* @brief Forcibly deletes the managed object.
* @param p A pointer (defaults to NULL).
*
* This object now @e owns the object pointed to by @a p. The
* previous object has been deleted.
*/
void
reset(element_type* __p = 0) throw()
{
if (__p != _M_ptr)
{
delete _M_ptr;
_M_ptr = __p;
}
}
/** @{
* @brief Automatic conversions
*
* These operations convert an %auto_ptr into and from an auto_ptr_ref
* automatically as needed. This allows constructs such as
* @code
* auto_ptr<Derived> func_returning_auto_ptr(.....);
* ...
* auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
* @endcode
*/
auto_ptr(auto_ptr_ref<element_type> __ref) throw()
: _M_ptr(__ref._M_ptr) { }
auto_ptr&
operator=(auto_ptr_ref<element_type> __ref) throw()
{
if (__ref._M_ptr != this->get())
{
delete _M_ptr;
_M_ptr = __ref._M_ptr;
}
return *this;
}
template<typename _Tp1>
operator auto_ptr_ref<_Tp1>() throw()
{ return auto_ptr_ref<_Tp1>(this->release()); }
template<typename _Tp1>
operator auto_ptr<_Tp1>() throw()
{ return auto_ptr<_Tp1>(this->release()); }
/** @} */
};
} // namespace std
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