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/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/assert.hpp>
17#include <boost/shared_ptr.hpp>
18#include <limits>
19
20namespace boost {
21namespace uuids {
22
23// generate a random-based uuid
24template <typename UniformRandomNumberGenerator>
25class basic_random_generator {
26private:
27 typedef uniform_int<unsigned long> distribution_type;
28 typedef variate_generator<UniformRandomNumberGenerator*, distribution_type> generator_type;
29
30 struct null_deleter
31 {
32 void operator()(void const *) const {}
33 };
34
35public:
36 typedef uuid result_type;
37
38 // default constructor creates the random number generator
39 basic_random_generator()
40 : pURNG(new UniformRandomNumberGenerator)
41 , generator
42 ( pURNG.get()
43 , distribution_type
44 ( (std::numeric_limits<unsigned long>::min)()
45 , (std::numeric_limits<unsigned long>::max)()
46 )
47 )
48 {
49 // seed the random number generator
50 detail::seed(*pURNG);
51 }
52
53 // keep a reference to a random number generator
54 // don't seed a given random number generator
55 explicit basic_random_generator(UniformRandomNumberGenerator& gen)
56 : pURNG(&gen, null_deleter())
57 , generator
58 ( pURNG.get()
59 , distribution_type
60 ( (std::numeric_limits<unsigned long>::min)()
61 , (std::numeric_limits<unsigned long>::max)()
62 )
63 )
64 {}
65
66 // keep a pointer to a random number generator
67 // don't seed a given random number generator
68 explicit basic_random_generator(UniformRandomNumberGenerator* pGen)
69 : pURNG(pGen, null_deleter())
70 , generator
71 ( pURNG.get()
72 , distribution_type
73 ( (std::numeric_limits<unsigned long>::min)()
74 , (std::numeric_limits<unsigned long>::max)()
75 )
76 )
77 {
78 BOOST_ASSERT(pURNG);
79 }
80
81 uuid operator()()
82 {
83 uuid u;
84
85 int i=0;
86 unsigned long random_value = generator();
87 for (uuid::iterator it=u.begin(); it!=u.end(); ++it, ++i) {
88 if (i==sizeof(unsigned long)) {
89 random_value = generator();
90 i = 0;
91 }
92
93 // static_cast gets rid of warnings of converting unsigned long to boost::uint8_t
94 *it = static_cast<uuid::value_type>((random_value >> (i*8)) & 0xFF);
95 }
96
97 // set variant
98 // must be 0b10xxxxxx
99 *(u.begin()+8) &= 0xBF;
100 *(u.begin()+8) |= 0x80;
101
102 // set version
103 // must be 0b0100xxxx
104 *(u.begin()+6) &= 0x4F; //0b01001111
105 *(u.begin()+6) |= 0x40; //0b01000000
106
107 return u;
108 }
109
110private:
111 shared_ptr<UniformRandomNumberGenerator> pURNG;
112 generator_type generator;
113};
114
115typedef basic_random_generator<mt19937> random_generator;
116
117}} // namespace boost::uuids
118
119#endif //BOOST_UUID_RANDOM_GENERATOR_HPP
120