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