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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 | ||
32 | namespace boost { | |
33 | namespace intrusive { | |
34 | namespace detail { | |
35 | ||
36 | template<class Parent, class Member> | |
37 | BOOST_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 | ||
91 | template<class Parent, class Member> | |
92 | BOOST_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 | ||
103 | template<class Parent, class Member> | |
104 | BOOST_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 |