mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
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71 lines
2.6 KiB
C++
71 lines
2.6 KiB
C++
/*=============================================================================
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Copyright (c) 2011-2013 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_DETAIL_INTEGER_STATIC_LOG2_HPP
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#define SPROUT_DETAIL_INTEGER_STATIC_LOG2_HPP
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#include <cstdint>
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#include <sprout/config.hpp>
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#include <sprout/type_traits/integral_constant.hpp>
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namespace sprout {
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namespace detail {
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typedef std::uintmax_t static_log2_argument_type;
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typedef int static_log2_result_type;
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namespace static_log2_impl {
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typedef sprout::detail::static_log2_argument_type argument_type;
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typedef sprout::detail::static_log2_result_type result_type;
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template<result_type n>
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struct choose_initial_n {
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SPROUT_STATIC_CONSTEXPR bool c
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= (sprout::detail::static_log2_impl::argument_type(1) << n << n) != 0
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;
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type value
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= !c * n + choose_initial_n<2 * c * n>::value
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;
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};
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template<>
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struct choose_initial_n<0> {
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type value = 0;
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};
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type n_zero = 16;
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type initial_n
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= sprout::detail::static_log2_impl::choose_initial_n<n_zero>::value
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;
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template<
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sprout::detail::static_log2_impl::argument_type x,
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sprout::detail::static_log2_impl::result_type n = sprout::detail::static_log2_impl::initial_n
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>
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struct static_log2_impl {
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SPROUT_STATIC_CONSTEXPR bool c = (x >> n) > 0;
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type value
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= c * n + (static_log2_impl<(x >> c * n), n / 2>::value)
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;
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};
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template<>
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struct static_log2_impl<1, 0> {
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SPROUT_STATIC_CONSTEXPR sprout::detail::static_log2_impl::result_type value = 0;
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};
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} // namespace static_log2_impl
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template<sprout::detail::static_log2_argument_type x>
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struct static_log2
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: public sprout::integral_constant<
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sprout::detail::static_log2_result_type,
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sprout::detail::static_log2_impl::static_log2_impl<x>::value
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>
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{};
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template<>
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struct static_log2<0> {};
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} // namespace detail
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} // namespace sprout
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#endif // #ifndef SPROUT_DETAIL_INTEGER_STATIC_LOG2_HPP
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