83 lines
1.6 KiB
C++
83 lines
1.6 KiB
C++
/*
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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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* Copyright (c) 2020 Andrey Semashev
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*/
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/*!
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* \file bit_operation_tools.hpp
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*
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* This file contains bit operation tools
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*/
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#ifndef BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_
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#define BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_
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#include <boost/predef/architecture/x86.h>
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#if BOOST_ARCH_X86
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#include <boost/atomic/detail/config.hpp>
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#include <boost/atomic/detail/header.hpp>
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#if defined(_MSC_VER)
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extern "C" unsigned char _BitScanForward(unsigned long* index, unsigned long x);
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#if defined(BOOST_MSVC)
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#pragma intrinsic(_BitScanForward)
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#endif
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#endif
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namespace boost {
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namespace atomics {
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namespace detail {
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//! Counts trailing zero bits
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BOOST_FORCEINLINE unsigned int count_trailing_zeros(unsigned int x)
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{
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#if defined(__GNUC__)
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return __builtin_ctz(x);
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#elif defined(_MSC_VER)
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unsigned long index;
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_BitScanForward(&index, x);
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return static_cast< unsigned int >(index);
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#else
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unsigned int index = 0u;
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if ((x & 0xFFFF) == 0u)
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{
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x >>= 16;
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index += 16u;
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}
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if ((x & 0xFF) == 0u)
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{
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x >>= 8;
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index += 8u;
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}
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if ((x & 0xF) == 0u)
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{
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x >>= 4;
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index += 4u;
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}
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if ((x & 0x3) == 0u)
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{
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x >>= 2;
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index += 2u;
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}
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if ((x & 0x1) == 0u)
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{
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index += 1u;
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}
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return index;
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#endif
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}
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} // namespace detail
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} // namespace atomics
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} // namespace boost
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#include <boost/atomic/detail/footer.hpp>
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#endif // BOOST_ARCH_X86
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#endif // BOOST_ATOMIC_BIT_OPERATION_TOOLS_HPP_INCLUDED_
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