// tagged pointer, for aba prevention
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//
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// Copyright (C) 2008, 2016 Tim Blechmann
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// 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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#ifndef BOOST_LOCKFREE_TAGGED_PTR_DCAS_HPP_INCLUDED
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#define BOOST_LOCKFREE_TAGGED_PTR_DCAS_HPP_INCLUDED
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#include <cstddef> /* for std::size_t */
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#include <limits>
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#include <boost/predef.h>
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namespace boost {
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namespace lockfree {
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namespace detail {
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template <class T>
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class
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#if BOOST_COMP_MSVC && BOOST_ARCH_X86_64
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BOOST_ALIGNMENT(16)
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#elif BOOST_COMP_MSVC && BOOST_ARCH_X86_32
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BOOST_ALIGNMENT(8)
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#else
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BOOST_ALIGNMENT(2 * sizeof(void*))
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#endif
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tagged_ptr
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{
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public:
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typedef std::size_t tag_t;
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/** uninitialized constructor */
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tagged_ptr(void) BOOST_NOEXCEPT//: ptr(0), tag(0)
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{}
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#ifdef BOOST_NO_CXX11_DEFAULTED_FUNCTIONS
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tagged_ptr(tagged_ptr const & p):
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ptr(p.ptr), tag(p.tag)
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{}
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#else
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tagged_ptr(tagged_ptr const & p) = default;
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#endif
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explicit tagged_ptr(T * p, tag_t t = 0):
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ptr(p), tag(t)
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{}
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/** unsafe set operation */
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/* @{ */
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#ifdef BOOST_NO_CXX11_DEFAULTED_FUNCTIONS
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tagged_ptr & operator= (tagged_ptr const & p)
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{
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set(p.ptr, p.tag);
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return *this;
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}
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#else
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tagged_ptr & operator= (tagged_ptr const & p) = default;
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#endif
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void set(T * p, tag_t t)
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{
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ptr = p;
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tag = t;
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}
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/* @} */
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/** comparing semantics */
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/* @{ */
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bool operator== (volatile tagged_ptr const & p) const
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{
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return (ptr == p.ptr) && (tag == p.tag);
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}
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bool operator!= (volatile tagged_ptr const & p) const
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{
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return !operator==(p);
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}
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/* @} */
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/** pointer access */
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/* @{ */
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T * get_ptr(void) const
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{
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return ptr;
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}
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void set_ptr(T * p)
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{
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ptr = p;
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}
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/* @} */
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/** tag access */
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/* @{ */
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tag_t get_tag() const
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{
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return tag;
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}
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tag_t get_next_tag() const
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{
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tag_t next = (get_tag() + 1) & (std::numeric_limits<tag_t>::max)();
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return next;
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}
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void set_tag(tag_t t)
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{
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tag = t;
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}
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/* @} */
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/** smart pointer support */
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/* @{ */
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T & operator*() const
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{
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return *ptr;
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}
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T * operator->() const
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{
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return ptr;
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}
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operator bool(void) const
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{
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return ptr != 0;
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}
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/* @} */
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protected:
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T * ptr;
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tag_t tag;
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};
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} /* namespace detail */
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} /* namespace lockfree */
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} /* namespace boost */
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#endif /* BOOST_LOCKFREE_TAGGED_PTR_DCAS_HPP_INCLUDED */
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