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/**
* @file llptrto.h
* @author Nat Goodspeed
* @date 2008-08-19
* @brief LLPtrTo<TARGET> is a template helper to pick either TARGET* or -- when
* TARGET is a subclass of LLRefCount or LLThreadSafeRefCount --
* LLPointer<TARGET>. LLPtrTo<> chooses whichever pointer type is best.
*
* $LicenseInfo:firstyear=2008&license=viewerlgpl$
* Second Life Viewer Source Code
* Copyright (C) 2010, Linden Research, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License only.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
* $/LicenseInfo$
*/
#if ! defined(LL_LLPTRTO_H)
#define LL_LLPTRTO_H
#include "llpointer.h"
#include "llrefcount.h" // LLRefCount
#include <boost/intrusive_ptr.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/type_traits/is_base_of.hpp>
#include <boost/type_traits/remove_pointer.hpp>
#include <memory> // std::shared_ptr, std::unique_ptr
#include <type_traits>
/**
* LLPtrTo<TARGET>::type is either of two things:
*
* * When TARGET is a subclass of either LLRefCount or LLThreadSafeRefCount,
* LLPtrTo<TARGET>::type is LLPointer<TARGET>.
* * Otherwise, LLPtrTo<TARGET>::type is TARGET*.
*
* This way, a class template can use LLPtrTo<TARGET>::type to select an
* appropriate pointer type to store.
*/
template <class T, class ENABLE=void>
struct LLPtrTo
{
typedef T* type;
};
/// specialize for subclasses of LLRefCount
template <class T>
struct LLPtrTo<T, typename std::enable_if< boost::is_base_of<LLRefCount, T>::value >::type>
{
typedef LLPointer<T> type;
};
/// specialize for subclasses of LLThreadSafeRefCount
template <class T>
struct LLPtrTo<T, typename std::enable_if< boost::is_base_of<LLThreadSafeRefCount, T>::value >::type>
{
typedef LLPointer<T> type;
};
/**
* LLRemovePointer<PTRTYPE>::type gets you the underlying (pointee) type.
*/
template <typename PTRTYPE>
struct LLRemovePointer
{
typedef typename boost::remove_pointer<PTRTYPE>::type type;
};
/// specialize for LLPointer<SOMECLASS>
template <typename SOMECLASS>
struct LLRemovePointer< LLPointer<SOMECLASS> >
{
typedef SOMECLASS type;
};
namespace LL
{
/*****************************************************************************
* get_ref()
*****************************************************************************/
template <typename T>
struct GetRef
{
// return const ref or non-const ref, depending on whether we can bind
// a non-const lvalue ref to the argument
const auto& operator()(const T& obj) const { return obj; }
auto& operator()(T& obj) const { return obj; }
};
template <typename T>
struct GetRef<const T*>
{
const auto& operator()(const T* ptr) const { return *ptr; }
};
template <typename T>
struct GetRef<T*>
{
auto& operator()(T* ptr) const { return *ptr; }
};
template <typename T>
struct GetRef< LLPointer<T> >
{
auto& operator()(LLPointer<T> ptr) const { return *ptr; }
};
/// whether we're passed a pointer or a reference, return a reference
template <typename T>
auto& get_ref(T& ptr_or_ref)
{
return GetRef<typename std::decay<T>::type>()(ptr_or_ref);
}
template <typename T>
const auto& get_ref(const T& ptr_or_ref)
{
return GetRef<typename std::decay<T>::type>()(ptr_or_ref);
}
/*****************************************************************************
* get_ptr()
*****************************************************************************/
// if T is any pointer type we recognize, return it unchanged
template <typename T>
const T* get_ptr(const T* ptr) { return ptr; }
template <typename T>
T* get_ptr(T* ptr) { return ptr; }
template <typename T>
const std::shared_ptr<T>& get_ptr(const std::shared_ptr<T>& ptr) { return ptr; }
template <typename T>
const std::unique_ptr<T>& get_ptr(const std::unique_ptr<T>& ptr) { return ptr; }
template <typename T>
const boost::shared_ptr<T>& get_ptr(const boost::shared_ptr<T>& ptr) { return ptr; }
template <typename T>
const boost::intrusive_ptr<T>& get_ptr(const boost::intrusive_ptr<T>& ptr) { return ptr; }
template <typename T>
const LLPointer<T>& get_ptr(const LLPointer<T>& ptr) { return ptr; }
// T is not any pointer type we recognize, take a pointer to the parameter
template <typename T>
const T* get_ptr(const T& obj) { return &obj; }
template <typename T>
T* get_ptr(T& obj) { return &obj; }
} // namespace LL
#endif /* ! defined(LL_LLPTRTO_H) */
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