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