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 // An implementation of minstd_rand that does not require
   9 // the Random library
  10
  11 #include <boost/cstdint.hpp>
  12
  13 namespace boost
  14 {
  15 namespace detail
  16 {
  17
  18 class minstd_rand
  19 {
  20 private:
  21
  22     boost::uint_least32_t x_;
  23
  24     enum { a = 48271, m = 2147483647 };
  25
  26 public:
  27
  28     minstd_rand(): x_( 1 )
  29     {
  30     }
  31
  32     explicit minstd_rand( boost::uint_least32_t x ): x_( x % m )
  33     {
  34         if( x_ == 0 )
  35         {
  36             x_ = 1;
  37         }
  38     }
  39
  40     boost::uint_least32_t operator()()
  41     {
  42         boost::uint_least64_t y = x_;
  43
  44         y = ( a * y ) % m;
  45
  46         x_ = static_cast<boost::uint_least32_t>( y );
  47
  48         return x_;
  49     }
  50 };
  51
  52 } // namespace detail
  53 } // namespace boost
  54
  55 #endif // #ifndef BOOST_UTILITY_DETAIL_MINSTD_RAND_HPP_INCLUDED