1/////////////////////////////////////////////////////////////////////////////
2//
3// (C) Copyright Ion Gaztanaga 2007-2013
4//
5// Distributed under the Boost Software License, Version 1.0.
6// (See accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8//
9// See http://www.boost.org/libs/intrusive for documentation.
10//
11/////////////////////////////////////////////////////////////////////////////
12#ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
13#define BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
14
15#ifndef BOOST_CONFIG_HPP
16# include <boost/config.hpp>
17#endif
18
19#if defined(BOOST_HAS_PRAGMA_ONCE)
20# pragma once
21#endif
22
23#include <boost/intrusive/detail/config_begin.hpp>
24#include <cstddef>
25
26#if defined(BOOST_MSVC) || ((defined(_WIN32) || defined(__WIN32__) || defined(WIN32)) && defined(BOOST_INTEL))
27 #define BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
28 #include <boost/static_assert.hpp>
29#endif
30
31namespace boost {
32namespace intrusive {
33namespace detail {
34
35template<class Parent, class Member>
36inline std::ptrdiff_t offset_from_pointer_to_member(const Member Parent::* ptr_to_member)
37{
38 //The implementation of a pointer to member is compiler dependent.
39 #if defined(BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER)
40
41 //MSVC compliant compilers use their the first 32 bits as offset (even in 64 bit mode)
42 union caster_union
43 {
44 const Member Parent::* ptr_to_member;
45 int offset;
46 } caster;
47
48 //MSVC ABI can use up to 3 int32 to represent pointer to member data
49 //with virtual base classes, in those cases there is no simple to
50 //obtain the address of the parent. So static assert to avoid runtime errors
51 BOOST_STATIC_ASSERT( sizeof(caster) == sizeof(int) );
52
53 caster.ptr_to_member = ptr_to_member;
54 return std::ptrdiff_t(caster.offset);
55 //Additional info on MSVC behaviour for the future. For 2/3 int ptr-to-member
56 //types dereference seems to be:
57 //
58 // vboffset = [compile_time_offset if 2-int ptr2memb] /
59 // [ptr2memb.i32[2] if 3-int ptr2memb].
60 // vbtable = *(this + vboffset);
61 // adj = vbtable[ptr2memb.i32[1]];
62 // var = adj + (this + vboffset) + ptr2memb.i32[0];
63 //
64 //To reverse the operation we need to
65 // - obtain vboffset (in 2-int ptr2memb implementation only)
66 // - Go to Parent's vbtable and obtain adjustment at index ptr2memb.i32[1]
67 // - parent = member - adj - vboffset - ptr2memb.i32[0]
68 //
69 //Even accessing to RTTI we might not be able to obtain this information
70 //so anyone who thinks it's possible, please send a patch.
71
72 //This works with gcc, msvc, ac++, ibmcpp
73 #elif defined(__GNUC__) || defined(__HP_aCC) || defined(BOOST_INTEL) || \
74 defined(__IBMCPP__) || defined(__DECCXX)
75 const Parent * const parent = 0;
76 const char *const member = static_cast<const char*>(static_cast<const void*>(&(parent->*ptr_to_member)));
77 return std::ptrdiff_t(member - static_cast<const char*>(static_cast<const void*>(parent)));
78 #else
79 //This is the traditional C-front approach: __MWERKS__, __DMC__, __SUNPRO_CC
80 union caster_union
81 {
82 const Member Parent::* ptr_to_member;
83 std::ptrdiff_t offset;
84 } caster;
85 caster.ptr_to_member = ptr_to_member;
86 return caster.offset - 1;
87 #endif
88}
89
90template<class Parent, class Member>
91inline Parent *parent_from_member(Member *member, const Member Parent::* ptr_to_member)
92{
93 return static_cast<Parent*>
94 (
95 static_cast<void*>
96 (
97 static_cast<char*>(static_cast<void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
98 )
99 );
100}
101
102template<class Parent, class Member>
103inline const Parent *parent_from_member(const Member *member, const Member Parent::* ptr_to_member)
104{
105 return static_cast<const Parent*>
106 (
107 static_cast<const void*>
108 (
109 static_cast<const char*>(static_cast<const void*>(member)) - offset_from_pointer_to_member(ptr_to_member)
110 )
111 );
112}
113
114} //namespace detail {
115} //namespace intrusive {
116} //namespace boost {
117
118#ifdef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
119#undef BOOST_INTRUSIVE_MSVC_ABI_PTR_TO_MEMBER
120#endif
121
122#include <boost/intrusive/detail/config_end.hpp>
123
124#endif //#ifndef BOOST_INTRUSIVE_DETAIL_PARENT_FROM_MEMBER_HPP
125