ceph/src/boost/boost/uuid/random_generator.hpp

   1 // Boost random_generator.hpp header file  ----------------------------------------------//
   2
   3 // Copyright 2010 Andy Tompkins.
   4 // Distributed under the Boost Software License, Version 1.0. (See
   5 // accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7
   8 #ifndef BOOST_UUID_RANDOM_GENERATOR_HPP
   9 #define BOOST_UUID_RANDOM_GENERATOR_HPP
  10
  11 #include <boost/uuid/uuid.hpp>
  12 #include <boost/uuid/detail/seed_rng.hpp>
  13 #include <boost/random/uniform_int.hpp>
  14 #include <boost/random/variate_generator.hpp>
  15 #include <boost/random/mersenne_twister.hpp>
  16 #include <boost/core/null_deleter.hpp>
  17 #include <boost/assert.hpp>
  18 #include <boost/shared_ptr.hpp>
  19 #include <limits>
  20
  21 namespace boost {
  22 namespace uuids {
  23
  24 // generate a random-based uuid
  25 template <typename UniformRandomNumberGenerator>
  26 class basic_random_generator {
  27 private:
  28     typedef uniform_int<unsigned long> distribution_type;
  29     typedef variate_generator<UniformRandomNumberGenerator*, distribution_type> generator_type;
  30
  31 public:
  32     typedef uuid result_type;
  33
  34     // default constructor creates the random number generator
  35     basic_random_generator()
  36         : pURNG(new UniformRandomNumberGenerator)
  37         , generator
  38           ( pURNG.get()
  39           , distribution_type
  40             ( (std::numeric_limits<unsigned long>::min)()
  41             , (std::numeric_limits<unsigned long>::max)()
  42             )
  43           )
  44     {
  45         // seed the random number generator
  46         detail::seed(*pURNG);
  47     }
  48
  49     // keep a reference to a random number generator
  50     // don't seed a given random number generator
  51     explicit basic_random_generator(UniformRandomNumberGenerator& gen)
  52         : pURNG(&gen, boost::null_deleter())
  53         , generator
  54           ( pURNG.get()
  55           , distribution_type
  56             ( (std::numeric_limits<unsigned long>::min)()
  57             , (std::numeric_limits<unsigned long>::max)()
  58             )
  59           )
  60     {}
  61
  62     // keep a pointer to a random number generator
  63     // don't seed a given random number generator
  64     explicit basic_random_generator(UniformRandomNumberGenerator* pGen)
  65         : pURNG(pGen, boost::null_deleter())
  66         , generator
  67           ( pURNG.get()
  68           , distribution_type
  69             ( (std::numeric_limits<unsigned long>::min)()
  70             , (std::numeric_limits<unsigned long>::max)()
  71             )
  72           )
  73     {
  74         BOOST_ASSERT(pURNG);
  75     }
  76
  77     uuid operator()()
  78     {
  79         uuid u;
  80
  81         int i=0;
  82         unsigned long random_value = generator();
  83         for (uuid::iterator it=u.begin(); it!=u.end(); ++it, ++i) {
  84             if (i==sizeof(unsigned long)) {
  85                 random_value = generator();
  86                 i = 0;
  87             }
  88
  89             // static_cast gets rid of warnings of converting unsigned long to boost::uint8_t
  90             *it = static_cast<uuid::value_type>((random_value >> (i*8)) & 0xFF);
  91         }
  92
  93         // set variant
  94         // must be 0b10xxxxxx
  95         *(u.begin()+8) &= 0xBF;
  96         *(u.begin()+8) |= 0x80;
  97
  98         // set version
  99         // must be 0b0100xxxx
 100         *(u.begin()+6) &= 0x4F; //0b01001111
 101         *(u.begin()+6) |= 0x40; //0b01000000
 102
 103         return u;
 104     }
 105
 106 private:
 107     shared_ptr<UniformRandomNumberGenerator> pURNG;
 108     generator_type generator;
 109 };
 110
 111 typedef basic_random_generator<mt19937> random_generator;
 112
 113 }} // namespace boost::uuids
 114
 115 #endif //BOOST_UUID_RANDOM_GENERATOR_HPP