ceph/src/boost/boost/utility/detail/minstd_rand.hpp

   1 #ifndef BOOST_UTILITY_DETAIL_MINSTD_RAND_HPP_INCLUDED
   2 #define BOOST_UTILITY_DETAIL_MINSTD_RAND_HPP_INCLUDED
   3
   4 // Copyright 2017 Peter Dimov
   5 //
   6 // Distributed under the Boost Software License, Version 1.0.
   7 //
   8 // See accompanying file LICENSE_1_0.txt or copy at
   9 // http://www.boost.org/LICENSE_1_0.txt
  10 //
  11 // An implementation of minstd_rand that does not require
  12 // the Random library
  13
  14 #include <boost/cstdint.hpp>
  15
  16 namespace boost
  17 {
  18 namespace detail
  19 {
  20
  21 class minstd_rand
  22 {
  23 private:
  24
  25     boost::uint_least32_t x_;
  26
  27     enum { a = 48271, m = 2147483647 };
  28
  29 public:
  30
  31     minstd_rand(): x_( 1 )
  32     {
  33     }
  34
  35     explicit minstd_rand( boost::uint_least32_t x ): x_( x % m )
  36     {
  37         if( x_ == 0 )
  38         {
  39             x_ = 1;
  40         }
  41     }
  42
  43     boost::uint_least32_t operator()()
  44     {
  45         boost::uint_least64_t y = x_;
  46
  47         y = ( a * y ) % m;
  48
  49         x_ = static_cast<boost::uint_least32_t>( y );
  50
  51         return x_;
  52     }
  53 };
  54
  55 } // namespace detail
  56 } // namespace boost
  57
  58 #endif // #ifndef BOOST_UTILITY_DETAIL_MINSTD_RAND_HPP_INCLUDED