40 lines
925 B
C++
40 lines
925 B
C++
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// -----------------------------------------------------------
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// lowest_bit.hpp
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//
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// Position of the lowest bit 'on'
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//
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// Copyright (c) 2003-2004, 2008 Gennaro Prota
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//
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// -----------------------------------------------------------
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#ifndef BOOST_LOWEST_BIT_HPP_GP_20030301
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#define BOOST_LOWEST_BIT_HPP_GP_20030301
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#include <assert.h>
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#include "boost/pending/integer_log2.hpp"
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namespace boost {
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template <typename T>
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int lowest_bit(T x) {
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assert(x >= 1); // PRE
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// clear all bits on except the rightmost one,
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// then calculate the logarithm base 2
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//
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return boost::integer_log2<T>( x - ( x & (x-1) ) );
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}
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}
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#endif // include guard
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