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/////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2007-2013
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/libs/intrusive for documentation.
//
/////////////////////////////////////////////////////////////////////////////
#ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
#define BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
#include <boost/intrusive/detail/config_begin.hpp>
#include <cstddef>
#if defined(BOOST_MSVC) || ((defined(_WIN32) || defined(__WIN32__) || defined(WIN32)) && defined(BOOST_INTEL))
#define BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
#include <boost/cstdint.hpp>
#include <boost/static_assert.hpp>
#endif
namespace boost {
namespace intrusive {
namespace detail {
template<class Parent, class Member>
inline std::ptrdiff_t offset_from_pointer_to_member(const Member Parent::* ptr_to_member)
{
//The implementation of a pointer to member is compiler dependent.
#if defined(BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER)
//MSVC compliant compilers use their the first 32 bits as offset (even in 64 bit mode)
union caster_union
{
const Member Parent::* ptr_to_member;
boost::int32_t offset;
} caster;
//MSVC ABI can use up to 3 int32 to represent pointer to member data
//with virtual base classes, in those cases there is no simple to
//obtain the address of the parent. So static assert to avoid runtime errors
BOOST_STATIC_ASSERT( sizeof(caster) == sizeof(boost::int32_t) );
caster.ptr_to_member = ptr_to_member;
return std::ptrdiff_t(caster.offset);
//Additional info on MSVC behaviour for the future. For 2/3 int ptr-to-member
//types dereference seems to be:
//
// vboffset = [compile_time_offset if 2-int ptr2memb] /
// [ptr2memb.i32[2] if 3-int ptr2memb].
// vbtable = *(this + vboffset);
// adj = vbtable[ptr2memb.i32[1]];
// var = adj + (this + vboffset) + ptr2memb.i32[0];
//
//To reverse the operation we need to
// - obtain vboffset (in 2-int ptr2memb implementation only)
// - Go to Parent's vbtable and obtain adjustment at index ptr2memb.i32[1]
// - parent = member - adj - vboffset - ptr2memb.i32[0]
//
//Even accessing to RTTI we might not be able to obtain this information
//so anyone who thinks it's possible, please send a patch.
//This works with gcc, msvc, ac++, ibmcpp
#elif defined(__GNUC__) || defined(__HP_aCC) || defined(BOOST_INTEL) || \
defined(__IBMCPP__) || defined(__DECCXX)
const Parent * const parent = 0;
const char *const member = static_cast<const char*>(static_cast<const void*>(&(parent->*ptr_to_member)));
return std::ptrdiff_t(member - static_cast<const char*>(static_cast<const void*>(parent)));
#else
//This is the traditional C-front approach: __MWERKS__, __DMC__, __SUNPRO_CC
union caster_union
{
const Member Parent::* ptr_to_member;
std::ptrdiff_t offset;
} caster;
caster.ptr_to_member = ptr_to_member;
return caster.offset - 1;
#endif
}
template<class Parent, class Member>
inline Parent *parent_from_member(Member *member, const Member Parent::* ptr_to_member)
{
return static_cast<Parent*>
(
static_cast<void*>
(
static_cast<char*>(static_cast<void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
)
);
}
template<class Parent, class Member>
inline const Parent *parent_from_member(const Member *member, const Member Parent::* ptr_to_member)
{
return static_cast<const Parent*>
(
static_cast<const void*>
(
static_cast<const char*>(static_cast<const void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
)
);
}
} //namespace detail {
} //namespace intrusive {
} //namespace boost {
#ifdef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
#undef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
#endif
#include <boost/intrusive/detail/config_end.hpp>
#endif //#ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
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