Chris@16: /////////////////////////////////////////////////////////////////////////////
Chris@16: //
Chris@16: // (C) Copyright Ion Gaztanaga  2007-2013
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0.
Chris@16: //    (See accompanying file LICENSE_1_0.txt or copy at
Chris@16: //          http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/intrusive for documentation.
Chris@16: //
Chris@16: /////////////////////////////////////////////////////////////////////////////
Chris@16: #ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
Chris@16: #define BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
Chris@16: 
Chris@101: #ifndef BOOST_CONFIG_HPP
Chris@101: #  include <boost/config.hpp>
Chris@101: #endif
Chris@101: 
Chris@101: #if defined(BOOST_HAS_PRAGMA_ONCE)
Chris@101: #  pragma once
Chris@101: #endif
Chris@101: 
Chris@16: #include <boost/intrusive/detail/config_begin.hpp>
Chris@16: #include <cstddef>
Chris@16: 
Chris@16: #if defined(BOOST_MSVC) || ((defined(_WIN32) || defined(__WIN32__) || defined(WIN32)) && defined(BOOST_INTEL))
Chris@16:    #define BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
Chris@16:    #include <boost/static_assert.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace intrusive {
Chris@16: namespace detail {
Chris@16: 
Chris@16: template<class Parent, class Member>
Chris@16: inline std::ptrdiff_t offset_from_pointer_to_member(const Member Parent::* ptr_to_member)
Chris@16: {
Chris@16:    //The implementation of a pointer to member is compiler dependent.
Chris@16:    #if defined(BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER)
Chris@16: 
Chris@16:    //MSVC compliant compilers use their the first 32 bits as offset (even in 64 bit mode)
Chris@16:    union caster_union
Chris@16:    {
Chris@16:       const Member Parent::* ptr_to_member;
Chris@101:       int offset;
Chris@16:    } caster;
Chris@16: 
Chris@16:    //MSVC ABI can use up to 3 int32 to represent pointer to member data
Chris@16:    //with virtual base classes, in those cases there is no simple to
Chris@16:    //obtain the address of the parent. So static assert to avoid runtime errors
Chris@101:    BOOST_STATIC_ASSERT( sizeof(caster) == sizeof(int) );
Chris@16: 
Chris@16:    caster.ptr_to_member = ptr_to_member;
Chris@16:    return std::ptrdiff_t(caster.offset);
Chris@101:    //Additional info on MSVC behaviour for the future. For 2/3 int ptr-to-member
Chris@16:    //types dereference seems to be:
Chris@16:    //
Chris@16:    // vboffset = [compile_time_offset if 2-int ptr2memb] /
Chris@16:    //            [ptr2memb.i32[2] if 3-int ptr2memb].
Chris@16:    // vbtable = *(this + vboffset);
Chris@16:    // adj = vbtable[ptr2memb.i32[1]];
Chris@16:    // var = adj + (this + vboffset) + ptr2memb.i32[0];
Chris@16:    //
Chris@16:    //To reverse the operation we need to
Chris@16:    // - obtain vboffset (in 2-int ptr2memb implementation only)
Chris@16:    // - Go to Parent's vbtable and obtain adjustment at index ptr2memb.i32[1]
Chris@16:    // - parent = member - adj - vboffset - ptr2memb.i32[0]
Chris@16:    //
Chris@16:    //Even accessing to RTTI we might not be able to obtain this information
Chris@16:    //so anyone who thinks it's possible, please send a patch.
Chris@16: 
Chris@16:    //This works with gcc, msvc, ac++, ibmcpp
Chris@16:    #elif defined(__GNUC__)   || defined(__HP_aCC) || defined(BOOST_INTEL) || \
Chris@16:          defined(__IBMCPP__) || defined(__DECCXX)
Chris@16:    const Parent * const parent = 0;
Chris@16:    const char *const member = static_cast<const char*>(static_cast<const void*>(&(parent->*ptr_to_member)));
Chris@16:    return std::ptrdiff_t(member - static_cast<const char*>(static_cast<const void*>(parent)));
Chris@16:    #else
Chris@16:    //This is the traditional C-front approach: __MWERKS__, __DMC__, __SUNPRO_CC
Chris@16:    union caster_union
Chris@16:    {
Chris@16:       const Member Parent::* ptr_to_member;
Chris@16:       std::ptrdiff_t offset;
Chris@16:    } caster;
Chris@16:    caster.ptr_to_member = ptr_to_member;
Chris@16:    return caster.offset - 1;
Chris@16:    #endif
Chris@16: }
Chris@16: 
Chris@16: template<class Parent, class Member>
Chris@16: inline Parent *parent_from_member(Member *member, const Member Parent::* ptr_to_member)
Chris@16: {
Chris@16:    return static_cast<Parent*>
Chris@16:       (
Chris@16:          static_cast<void*>
Chris@16:          (
Chris@16:             static_cast<char*>(static_cast<void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
Chris@16:          )
Chris@16:       );
Chris@16: }
Chris@16: 
Chris@16: template<class Parent, class Member>
Chris@16: inline const Parent *parent_from_member(const Member *member, const Member Parent::* ptr_to_member)
Chris@16: {
Chris@16:    return static_cast<const Parent*>
Chris@16:       (
Chris@16:          static_cast<const void*>
Chris@16:          (
Chris@16:             static_cast<const char*>(static_cast<const void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
Chris@16:          )
Chris@16:       );
Chris@16: }
Chris@16: 
Chris@16: }  //namespace detail {
Chris@16: }  //namespace intrusive {
Chris@16: }  //namespace boost {
Chris@16: 
Chris@16: #ifdef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
Chris@16: #undef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
Chris@16: #endif
Chris@16: 
Chris@16: #include <boost/intrusive/detail/config_end.hpp>
Chris@16: 
Chris@16: #endif   //#ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP