diff -r 666f914201fb -r 2fe1408b6811 epoc32/include/stdapis/boost/pending/integer_log2.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/epoc32/include/stdapis/boost/pending/integer_log2.hpp Tue Mar 16 16:12:26 2010 +0000 @@ -0,0 +1,113 @@ +// ------------------------------------- +// integer_log2.hpp +// +// Gives the integer part of the logarithm, in base 2, of a +// given number. Behavior is undefined if the argument is <= 0. +// +// +// (C) Copyright Gennaro Prota 2003 - 2004. +// +// 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) +// +// ------------------------------------------------------ + + + +#ifndef BOOST_INTEGER_LOG2_HPP_GP_20030301 +#define BOOST_INTEGER_LOG2_HPP_GP_20030301 + +#include +#include // actually used for Borland only +#include "boost/limits.hpp" +#include "boost/config.hpp" + + +namespace boost { + namespace detail { + + template + int integer_log2_impl(T x, int n) { + + int result = 0; + + while (x != 1) { + + const T t = x >> n; + if (t) { + result += n; + x = t; + } + n /= 2; + + } + + return result; + } + + + + // helper to find the maximum power of two + // less than p (more involved than necessary, + // to avoid PTS) + // + template + struct max_pow2_less { + + enum { c = 2*n < p }; + + BOOST_STATIC_CONSTANT(int, value = + c ? (max_pow2_less< c*p, 2*c*n>::value) : n); + + }; + + template <> + struct max_pow2_less<0, 0> { + + BOOST_STATIC_CONSTANT(int, value = 0); + }; + + // this template is here just for Borland :( + // we could simply rely on numeric_limits but sometimes + // Borland tries to use numeric_limits, because + // of its usual const-related problems in argument deduction + // - gps + template + struct width { + +#ifdef __BORLANDC__ + BOOST_STATIC_CONSTANT(int, value = sizeof(T) * CHAR_BIT); +#else + BOOST_STATIC_CONSTANT(int, value = (std::numeric_limits::digits)); +#endif + + }; + + } // detail + + + // --------- + // integer_log2 + // --------------- + // + template + int integer_log2(T x) { + + assert(x > 0); + + const int n = detail::max_pow2_less< + detail::width :: value, 4 + > :: value; + + return detail::integer_log2_impl(x, n); + + } + + + +} + + + +#endif // include guard