mirror of
https://github.com/bolero-MURAKAMI/Sprout
synced 2024-11-12 21:09:01 +00:00
75 lines
2.3 KiB
C++
75 lines
2.3 KiB
C++
/*=============================================================================
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Copyright (c) 2011-2017 Bolero MURAKAMI
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https://github.com/bolero-MURAKAMI/Sprout
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef SPROUT_INTEGER_CARRY_TO_EXP2_HPP
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#define SPROUT_INTEGER_CARRY_TO_EXP2_HPP
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#include <climits>
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#include <limits>
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#include <sprout/config.hpp>
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#include <sprout/bit/cntl0.hpp>
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#include <sprout/bit/popcount.hpp>
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#include <sprout/type_traits/is_sint.hpp>
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#include <sprout/type_traits/is_uint.hpp>
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#include <sprout/type_traits/enabler_if.hpp>
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namespace sprout {
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namespace detail {
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template<typename IntType>
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inline SPROUT_CONSTEXPR IntType
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carry_to_exp2_simpl(IntType x) {
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return sprout::popcount(x) <= 1 ? x
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: IntType(1) << (sizeof(IntType) * CHAR_BIT - sprout::cntl0(x))
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;
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}
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template<typename UIntType>
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inline SPROUT_CONSTEXPR UIntType
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carry_to_exp2_uimpl(int n) {
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return !n ? UIntType(0)
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: UIntType(1) << (sizeof(UIntType) * CHAR_BIT - n)
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;
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}
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} // namespace detail
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//
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// carry_to_exp2
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//
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// note: for signed integer
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// x == MIN
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// --> carry_to_exp2(x) returns x .
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// x < 0
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// --> carry_to_exp2(x) returns -carry_to_exp2(-x) .
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// -(MIN / 2) < x
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// --> carry_to_exp2(x) returns MIN .
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//
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// note: for unsigned integer
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// MAX / 2 + 1 < x
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// --> carry_to_exp2(x) returns 0 .
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//
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template<
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typename IntType,
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typename sprout::enabler_if<sprout::is_sint<IntType>::value>::type = sprout::enabler
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>
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inline SPROUT_CONSTEXPR IntType
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carry_to_exp2(IntType x) {
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return x == std::numeric_limits<IntType>::min() ? x
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: x < IntType(0) ? -sprout::detail::carry_to_exp2_simpl(-x)
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: sprout::detail::carry_to_exp2_simpl(x)
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;
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}
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template<
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typename UIntType,
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typename sprout::enabler_if<sprout::is_uint<UIntType>::value>::type = sprout::enabler
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>
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inline SPROUT_CONSTEXPR UIntType
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carry_to_exp2(UIntType x) {
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return sprout::popcount(x) <= 1 ? x
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: sprout::detail::carry_to_exp2_uimpl<UIntType>(sprout::cntl0(x))
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;
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}
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} // namespace sprout
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#endif // #ifndef SPROUT_INTEGER_CARRY_TO_EXP2_HPP
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