diff options
Diffstat (limited to 'contrib/src/boost/integer/static_log2.hpp')
-rw-r--r-- | contrib/src/boost/integer/static_log2.hpp | 254 |
1 files changed, 127 insertions, 127 deletions
diff --git a/contrib/src/boost/integer/static_log2.hpp b/contrib/src/boost/integer/static_log2.hpp index 2d3b8c0..56c7a00 100644 --- a/contrib/src/boost/integer/static_log2.hpp +++ b/contrib/src/boost/integer/static_log2.hpp @@ -1,127 +1,127 @@ -// -------------- Boost static_log2.hpp header file ----------------------- //
-//
-// Copyright (C) 2001 Daryle Walker.
-// Copyright (C) 2003 Vesa Karvonen.
-// Copyright (C) 2003 Gennaro Prota.
-//
-// 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/libs/integer for documentation.
-// ------------------------------------------------------------------------- //
-
-
-#ifndef BOOST_INTEGER_STATIC_LOG2_HPP
-#define BOOST_INTEGER_STATIC_LOG2_HPP
-
-#include "boost/integer_fwd.hpp" // for boost::intmax_t
-
-namespace boost {
-
- namespace detail {
-
- namespace static_log2_impl {
-
- // choose_initial_n<>
- //
- // Recursively doubles its integer argument, until it
- // becomes >= of the "width" (C99, 6.2.6.2p4) of
- // static_log2_argument_type.
- //
- // Used to get the maximum power of two less then the width.
- //
- // Example: if on your platform argument_type has 48 value
- // bits it yields n=32.
- //
- // It's easy to prove that, starting from such a value
- // of n, the core algorithm works correctly for any width
- // of static_log2_argument_type and that recursion always
- // terminates with x = 1 and n = 0 (see the algorithm's
- // invariant).
-
- typedef boost::static_log2_argument_type argument_type;
- typedef boost::static_log2_result_type result_type;
-
- template <result_type n>
- struct choose_initial_n {
-
- BOOST_STATIC_CONSTANT(bool, c = (argument_type(1) << n << n) != 0);
- BOOST_STATIC_CONSTANT(
- result_type,
- value = !c*n + choose_initial_n<2*c*n>::value
- );
-
- };
-
- template <>
- struct choose_initial_n<0> {
- BOOST_STATIC_CONSTANT(result_type, value = 0);
- };
-
-
-
- // start computing from n_zero - must be a power of two
- const result_type n_zero = 16;
- const result_type initial_n = choose_initial_n<n_zero>::value;
-
- // static_log2_impl<>
- //
- // * Invariant:
- // 2n
- // 1 <= x && x < 2 at the start of each recursion
- // (see also choose_initial_n<>)
- //
- // * Type requirements:
- //
- // argument_type maybe any unsigned type with at least n_zero + 1
- // value bits. (Note: If larger types will be standardized -e.g.
- // unsigned long long- then the argument_type typedef can be
- // changed without affecting the rest of the code.)
- //
-
- template <argument_type x, result_type n = initial_n>
- struct static_log2_impl {
-
- BOOST_STATIC_CONSTANT(bool, c = (x >> n) > 0); // x >= 2**n ?
- BOOST_STATIC_CONSTANT(
- result_type,
- value = c*n + (static_log2_impl< (x>>c*n), n/2 >::value)
- );
-
- };
-
- template <>
- struct static_log2_impl<1, 0> {
- BOOST_STATIC_CONSTANT(result_type, value = 0);
- };
-
- }
- } // detail
-
-
-
- // --------------------------------------
- // static_log2<x>
- // ----------------------------------------
-
- template <static_log2_argument_type x>
- struct static_log2 {
-
- BOOST_STATIC_CONSTANT(
- static_log2_result_type,
- value = detail::static_log2_impl::static_log2_impl<x>::value
- );
-
- };
-
-
- template <>
- struct static_log2<0> { };
-
-}
-
-
-
-#endif // include guard
+// -------------- Boost static_log2.hpp header file ----------------------- // +// +// Copyright (C) 2001 Daryle Walker. +// Copyright (C) 2003 Vesa Karvonen. +// Copyright (C) 2003 Gennaro Prota. +// +// 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/libs/integer for documentation. +// ------------------------------------------------------------------------- // + + +#ifndef BOOST_INTEGER_STATIC_LOG2_HPP +#define BOOST_INTEGER_STATIC_LOG2_HPP + +#include "boost/integer_fwd.hpp" // for boost::intmax_t + +namespace boost { + + namespace detail { + + namespace static_log2_impl { + + // choose_initial_n<> + // + // Recursively doubles its integer argument, until it + // becomes >= of the "width" (C99, 6.2.6.2p4) of + // static_log2_argument_type. + // + // Used to get the maximum power of two less then the width. + // + // Example: if on your platform argument_type has 48 value + // bits it yields n=32. + // + // It's easy to prove that, starting from such a value + // of n, the core algorithm works correctly for any width + // of static_log2_argument_type and that recursion always + // terminates with x = 1 and n = 0 (see the algorithm's + // invariant). + + typedef boost::static_log2_argument_type argument_type; + typedef boost::static_log2_result_type result_type; + + template <result_type n> + struct choose_initial_n { + + BOOST_STATIC_CONSTANT(bool, c = (argument_type(1) << n << n) != 0); + BOOST_STATIC_CONSTANT( + result_type, + value = !c*n + choose_initial_n<2*c*n>::value + ); + + }; + + template <> + struct choose_initial_n<0> { + BOOST_STATIC_CONSTANT(result_type, value = 0); + }; + + + + // start computing from n_zero - must be a power of two + const result_type n_zero = 16; + const result_type initial_n = choose_initial_n<n_zero>::value; + + // static_log2_impl<> + // + // * Invariant: + // 2n + // 1 <= x && x < 2 at the start of each recursion + // (see also choose_initial_n<>) + // + // * Type requirements: + // + // argument_type maybe any unsigned type with at least n_zero + 1 + // value bits. (Note: If larger types will be standardized -e.g. + // unsigned long long- then the argument_type typedef can be + // changed without affecting the rest of the code.) + // + + template <argument_type x, result_type n = initial_n> + struct static_log2_impl { + + BOOST_STATIC_CONSTANT(bool, c = (x >> n) > 0); // x >= 2**n ? + BOOST_STATIC_CONSTANT( + result_type, + value = c*n + (static_log2_impl< (x>>c*n), n/2 >::value) + ); + + }; + + template <> + struct static_log2_impl<1, 0> { + BOOST_STATIC_CONSTANT(result_type, value = 0); + }; + + } + } // detail + + + + // -------------------------------------- + // static_log2<x> + // ---------------------------------------- + + template <static_log2_argument_type x> + struct static_log2 { + + BOOST_STATIC_CONSTANT( + static_log2_result_type, + value = detail::static_log2_impl::static_log2_impl<x>::value + ); + + }; + + + template <> + struct static_log2<0> { }; + +} + + + +#endif // include guard |