//
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// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/beast
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//
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#ifndef BOOST_BEAST_CORE_DETAIL_PCG_HPP
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#define BOOST_BEAST_CORE_DETAIL_PCG_HPP
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#include <boost/core/ignore_unused.hpp>
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#include <cstdint>
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#include <random>
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namespace boost {
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namespace beast {
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namespace detail {
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class pcg
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{
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std::uint64_t state_ = 0;
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std::uint64_t increment_;
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public:
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using result_type = std::uint32_t;
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// Initialize the generator.
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// There are no restrictions on the input values.
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pcg(
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std::uint64_t seed,
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std::uint64_t stream)
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{
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// increment must be odd
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increment_ = 2 * stream + 1;
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boost::ignore_unused((*this)());
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state_ += seed;
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boost::ignore_unused((*this)());
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}
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std::uint32_t
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operator()()
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{
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std::uint64_t const p = state_;
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state_ = p *
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6364136223846793005ULL +
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increment_;
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std::uint32_t const x =
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static_cast<std::uint32_t>(
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((p >> 18) ^ p) >> 27);
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std::uint32_t const r = p >> 59;
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#ifdef BOOST_MSVC
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return _rotr(x, r);
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#else
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return (x >> r) | (x << ((1 + ~r) & 31));
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#endif
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}
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};
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} // detail
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} // beast
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} // boost
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#endif
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