/Src/Dependencies/Boost/boost/random/detail/integer_log2.hpp
http://hadesmem.googlecode.com/ · C++ Header · 72 lines · 49 code · 9 blank · 14 comment · 3 complexity · 3003967f341e362460ad8d35a4482e4e MD5 · raw file
- /* 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: integer_log2.hpp 72861 2011-07-02 20:26:19Z danieljames $
- *
- */
- #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 {
- // Daniel James: Disabled use of constexpr because integer_log2_impl is not a
- // valid constexpr.
- #if 0 && !defined(BOOST_NO_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 __attribute__((const)) __attribute__((always_inline))
- #else
- #define BOOST_RANDOM_DETAIL_CONSTEXPR inline
- #endif
- template<int Shift>
- struct integer_log2_impl
- {
- 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);
- }
- };
- 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