mirror of
https://github.com/bolero-MURAKAMI/Sprout.git
synced 2024-11-14 10:39:05 +00:00
115 lines
3.8 KiB
C++
115 lines
3.8 KiB
C++
/*=============================================================================
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Copyright (c) 2011-2014 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_BIT_CLZ_HPP
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#define SPROUT_BIT_CLZ_HPP
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#include <cstddef>
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#include <climits>
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#include <type_traits>
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#include <sprout/config.hpp>
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#include <sprout/utility/pair/pair.hpp>
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#include <sprout/bit/shlr.hpp>
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#include <sprout/bit/shll.hpp>
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namespace sprout {
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namespace detail {
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# if SPROUT_USE_BUILTIN_BIT_OPERATION
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inline SPROUT_CONSTEXPR int
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clz_non0(unsigned x) {
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return __builtin_clz(x);
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}
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inline SPROUT_CONSTEXPR int
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clz_non0(unsigned long x) {
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return __builtin_clzl(x);
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}
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inline SPROUT_CONSTEXPR int
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clz_non0(unsigned long long x) {
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return __builtin_clzll(x);
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}
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# endif
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template<std::size_t N, typename Integral>
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inline SPROUT_CONSTEXPR typename std::enable_if<
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(N == 1),
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sprout::pair<Integral, int>
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>::type
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clz_bytes(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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return xn;
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}
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template<std::size_t N, typename Integral>
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inline SPROUT_CONSTEXPR typename std::enable_if<
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(N > 1),
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sprout::pair<Integral, int>
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>::type
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clz_bytes(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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typedef sprout::pair<Integral, int> type;
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return sprout::detail::clz_bytes<N / 2>(
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sprout::shlr(xn.first, (sizeof(Integral) - N / 2) * CHAR_BIT) ? xn
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: type(sprout::shll(xn.first, N / 2 * CHAR_BIT), xn.second + N / 2 * CHAR_BIT)
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);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR sprout::pair<Integral, int>
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clz_bytes(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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return sprout::detail::clz_bytes<sizeof(Integral)>(xn);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz_bits1(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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return xn.second - sprout::shlr(xn.first, sizeof(Integral) * CHAR_BIT - 1);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz_bits2(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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typedef sprout::pair<Integral, int> type;
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return sprout::detail::clz_bits1(
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sprout::shlr(xn.first, sizeof(Integral) * CHAR_BIT - 2) ? xn
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: type(sprout::shll(xn.first, 2), xn.second + 2)
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);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz_bits4(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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typedef sprout::pair<Integral, int> type;
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return sprout::detail::clz_bits2(
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sprout::shlr(xn.first, sizeof(Integral) * CHAR_BIT - 4) ? xn
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: type(sprout::shll(xn.first, 4), xn.second + 4)
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);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz_bits(sprout::pair<Integral, int> const& xn) SPROUT_NOEXCEPT {
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return sprout::detail::clz_bits4(xn);
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz_non0(Integral x) SPROUT_NOEXCEPT {
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typedef sprout::pair<Integral, int> type;
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return sprout::detail::clz_bits(sprout::detail::clz_bytes(type(x, 1)));
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}
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template<typename Integral>
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inline SPROUT_CONSTEXPR int
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clz(Integral x) SPROUT_NOEXCEPT {
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return x == 0 ? static_cast<int>(sizeof(x) * CHAR_BIT)
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: sprout::detail::clz_non0(x)
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;
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}
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} // namespace detail
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//
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// clz
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//
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template<typename Integral>
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inline SPROUT_CONSTEXPR typename std::enable_if<
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std::is_integral<Integral>::value,
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int
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>::type
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clz(Integral x) SPROUT_NOEXCEPT {
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return sprout::detail::clz(x);
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}
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} // namespace sprout
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#endif // #ifndef SPROUT_BIT_CLZ_HPP
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