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Diffstat (limited to 'src/third_party/boost-1.60.0/boost/random/detail/integer_log2.hpp')
-rw-r--r-- | src/third_party/boost-1.60.0/boost/random/detail/integer_log2.hpp | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/src/third_party/boost-1.60.0/boost/random/detail/integer_log2.hpp b/src/third_party/boost-1.60.0/boost/random/detail/integer_log2.hpp new file mode 100644 index 00000000000..248243a4b2e --- /dev/null +++ b/src/third_party/boost-1.60.0/boost/random/detail/integer_log2.hpp @@ -0,0 +1,84 @@ +/* boost random/detail/integer_log2.hpp header file + * + * Copyright Steven Watanabe 2011 + * Distributed under the Boost Software License, Version 1.0. (See + * accompanying file LICENSE_1_0.txt or copy at + * http://www.boost.org/LICENSE_1_0.txt) + * + * See http://www.boost.org for most recent version including documentation. + * + * $Id$ + * + */ + +#ifndef BOOST_RANDOM_DETAIL_INTEGER_LOG2_HPP +#define BOOST_RANDOM_DETAIL_INTEGER_LOG2_HPP + +#include <boost/config.hpp> +#include <boost/limits.hpp> +#include <boost/pending/integer_log2.hpp> + +namespace boost { +namespace random { +namespace detail { + +#if !defined(BOOST_NO_CXX11_CONSTEXPR) +#define BOOST_RANDOM_DETAIL_CONSTEXPR constexpr +#elif defined(BOOST_MSVC) +#define BOOST_RANDOM_DETAIL_CONSTEXPR __forceinline +#elif defined(__GNUC__) && __GNUC__ >= 4 +#define BOOST_RANDOM_DETAIL_CONSTEXPR inline __attribute__((__const__)) __attribute__((__always_inline__)) +#else +#define BOOST_RANDOM_DETAIL_CONSTEXPR inline +#endif + +template<int Shift> +struct integer_log2_impl +{ +#if defined(BOOST_NO_CXX11_CONSTEXPR) + template<class T> + BOOST_RANDOM_DETAIL_CONSTEXPR static int apply(T t, int accum) + { + int update = ((t >> Shift) != 0) * Shift; + return integer_log2_impl<Shift / 2>::apply(t >> update, accum + update); + } +#else + template<class T> + BOOST_RANDOM_DETAIL_CONSTEXPR static int apply2(T t, int accum, int update) + { + return integer_log2_impl<Shift / 2>::apply(t >> update, accum + update); + } + + template<class T> + BOOST_RANDOM_DETAIL_CONSTEXPR static int apply(T t, int accum) + { + return apply2(t, accum, ((t >> Shift) != 0) * Shift); + } +#endif +}; + +template<> +struct integer_log2_impl<1> +{ + template<class T> + BOOST_RANDOM_DETAIL_CONSTEXPR static int apply(T t, int accum) + { + return int(t >> 1) + accum; + } +}; + +template<class T> +BOOST_RANDOM_DETAIL_CONSTEXPR int integer_log2(T t) +{ + return integer_log2_impl< + ::boost::detail::max_pow2_less< + ::std::numeric_limits<T>::digits, 4 + >::value + >::apply(t, 0); +} + +} // namespace detail +} // namespace random +} // namespace boost + +#endif // BOOST_RANDOM_DETAIL_INTEGER_LOG2_HPP |