Chris@16: // Boost seed_rng.hpp header file  ----------------------------------------------//
Chris@16: 
Chris@16: // Copyright 2007 Andy Tompkins.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: // Revision History
Chris@16: //  09 Nov 2007 - Initial Revision
Chris@16: //  25 Feb 2008 - moved to namespace boost::uuids::detail
Chris@16: //  28 Nov 2009 - disabled deprecated warnings for MSVC
Chris@16: 
Chris@16: // seed_rng models a UniformRandomNumberGenerator (see Boost.Random).
Chris@16: // Random number generators are hard to seed well.  This is intended to provide
Chris@16: // good seed values for random number generators.
Chris@16: // It creates random numbers from a sha1 hash of data from a variary of sources,
Chris@16: // all of which are standard function calls.  It produces random numbers slowly.
Chris@16: // Peter Dimov provided the details of sha1_random_digest_().
Chris@16: // see http://archives.free.net.ph/message/20070507.175609.4c4f503a.en.html
Chris@16: 
Chris@16: #ifndef BOOST_UUID_SEED_RNG_HPP
Chris@16: #define BOOST_UUID_SEED_RNG_HPP
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: #include <cstring> // for memcpy
Chris@16: #include <limits>
Chris@16: #include <ctime> // for time_t, time, clock_t, clock
Chris@16: #include <cstdlib> // for rand
Chris@16: #include <cstdio> // for FILE, fopen, fread, fclose
Chris@16: #include <boost/uuid/sha1.hpp>
Chris@16: //#include <boost/nondet_random.hpp> //forward declare boost::random::random_device
Chris@16: 
Chris@16: // can't use boost::generator_iterator since boost::random number seed(Iter&, Iter)
Chris@16: // functions need a last iterator
Chris@16: //#include <boost/generator_iterator.hpp>
Chris@16: # include <boost/iterator/iterator_facade.hpp>
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma warning(push) // Save warning settings.
Chris@16: #pragma warning(disable : 4996) // Disable deprecated std::fopen
Chris@16: #endif
Chris@16: 
Chris@16: #ifdef BOOST_NO_STDC_NAMESPACE
Chris@16: namespace std {
Chris@16:     using ::memcpy;
Chris@16:     using ::time_t;
Chris@16:     using ::time;
Chris@16:     using ::clock_t;
Chris@16:     using ::clock;
Chris@16:     using ::rand;
Chris@16:     using ::FILE;
Chris@16:     using ::fopen;
Chris@16:     using ::fread;
Chris@16:     using ::fclose;
Chris@16: } //namespace std
Chris@16: #endif
Chris@16: 
Chris@16: // forward declare random number generators
Chris@16: namespace boost { namespace random {
Chris@16: class random_device;
Chris@16: }} //namespace boost::random
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace uuids {
Chris@16: namespace detail {
Chris@16: 
Chris@16: // should this be part of Boost.Random?
Chris@16: class seed_rng
Chris@16: {
Chris@16: public:
Chris@16:     typedef unsigned int result_type;
Chris@16:     BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
Chris@16:     //BOOST_STATIC_CONSTANT(unsigned int, min_value = 0);
Chris@16:     //BOOST_STATIC_CONSTANT(unsigned int, max_value = UINT_MAX);
Chris@16: 
Chris@16: public:
Chris@16:     // note: rd_ intentionally left uninitialized
Chris@16:     seed_rng()
Chris@16:         : rd_index_(5)
Chris@16:         , random_(std::fopen( "/dev/urandom", "rb" ))
Chris@16:     {}
Chris@16: 
Chris@16:     ~seed_rng()
Chris@16:     {
Chris@16:         if (random_) {
Chris@16:             std::fclose(random_);
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const
Chris@16:     {
Chris@16:         return (std::numeric_limits<result_type>::min)();
Chris@16:     }
Chris@16:     result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const
Chris@16:     {
Chris@16:         return (std::numeric_limits<result_type>::max)();
Chris@16:     }
Chris@16: 
Chris@16:     result_type operator()()
Chris@16:     {
Chris@16:         if (rd_index_ >= 5) {
Chris@16:             //get new digest
Chris@16:             sha1_random_digest_();
Chris@16: 
Chris@16:             rd_index_ = 0;
Chris@16:         }
Chris@16: 
Chris@16:         return rd_[rd_index_++];
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     inline void ignore_size(size_t) {}
Chris@16: 
Chris@16:     static unsigned int * sha1_random_digest_state_()
Chris@16:     {
Chris@16:         static unsigned int state[ 5 ];
Chris@16:         return state;
Chris@16:     }
Chris@16: 
Chris@16:     void sha1_random_digest_()
Chris@16:     {
Chris@16:         boost::uuids::detail::sha1 sha;
Chris@16: 
Chris@16:         unsigned int * ps = sha1_random_digest_state_();
Chris@16: 
Chris@16:         unsigned int state[ 5 ];
Chris@16:         std::memcpy( state, ps, sizeof( state ) ); // harmless data race
Chris@16: 
Chris@16:         sha.process_bytes( (unsigned char const*)state, sizeof( state ) );
Chris@16:         sha.process_bytes( (unsigned char const*)&ps, sizeof( ps ) );
Chris@16: 
Chris@16:         {
Chris@16:             std::time_t tm = std::time( 0 );
Chris@16:             sha.process_bytes( (unsigned char const*)&tm, sizeof( tm ) );
Chris@16:         }
Chris@16: 
Chris@16:         {
Chris@16:             std::clock_t ck = std::clock();
Chris@16:             sha.process_bytes( (unsigned char const*)&ck, sizeof( ck ) );
Chris@16:         }
Chris@16: 
Chris@16:         {
Chris@16:             unsigned int rn[] =
Chris@16:                 { static_cast<unsigned int>(std::rand())
Chris@16:                 , static_cast<unsigned int>(std::rand())
Chris@16:                 , static_cast<unsigned int>(std::rand())
Chris@16:                 };
Chris@16:             sha.process_bytes( (unsigned char const*)rn, sizeof( rn ) );
Chris@16:         }
Chris@16: 
Chris@16:         {
Chris@16:             // intentionally left uninitialized
Chris@16:             unsigned char buffer[ 20 ];
Chris@16: 
Chris@16:             if(random_)
Chris@16:             {
Chris@16:                 ignore_size(std::fread( buffer, 1, 20, random_ ));
Chris@16:             }
Chris@16: 
Chris@16:             // using an uninitialized buffer[] if fopen fails
Chris@16:             // intentional, we rely on its contents being random
Chris@16:             sha.process_bytes( buffer, sizeof( buffer ) );
Chris@16:         }
Chris@16: 
Chris@16:         {
Chris@16:             // *p is intentionally left uninitialized
Chris@16:             unsigned int * p = new unsigned int;
Chris@16: 
Chris@16:             sha.process_bytes( (unsigned char const*)p, sizeof( *p ) );
Chris@16:             sha.process_bytes( (unsigned char const*)&p, sizeof( p ) );
Chris@16: 
Chris@16:             delete p;
Chris@16:         }
Chris@16: 
Chris@16:         sha.process_bytes( (unsigned char const*)rd_, sizeof( rd_ ) );
Chris@16: 
Chris@16:         unsigned int digest[ 5 ];
Chris@16:         sha.get_digest( digest );
Chris@16: 
Chris@16:         for( int i = 0; i < 5; ++i )
Chris@16:         {
Chris@16:             // harmless data race
Chris@16:             ps[ i ] ^= digest[ i ];
Chris@16:             rd_[ i ] ^= digest[ i ];
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16: private:
Chris@16:     unsigned int rd_[5];
Chris@16:     int rd_index_;
Chris@16:     std::FILE * random_;
Chris@16: 
Chris@16: private: // make seed_rng noncopyable
Chris@16:     seed_rng(seed_rng const&);
Chris@16:     seed_rng& operator=(seed_rng const&);
Chris@16: };
Chris@16: 
Chris@16: // almost a copy of boost::generator_iterator
Chris@16: // but default constructor sets m_g to NULL
Chris@16: template <class Generator>
Chris@16: class generator_iterator
Chris@16:   : public iterator_facade<
Chris@16:         generator_iterator<Generator>
Chris@16:       , typename Generator::result_type
Chris@16:       , single_pass_traversal_tag
Chris@16:       , typename Generator::result_type const&
Chris@16:     >
Chris@16: {
Chris@16:     typedef iterator_facade<
Chris@16:         generator_iterator<Generator>
Chris@16:       , typename Generator::result_type
Chris@16:       , single_pass_traversal_tag
Chris@16:       , typename Generator::result_type const&
Chris@16:     > super_t;
Chris@16: 
Chris@16:  public:
Chris@16:     generator_iterator() : m_g(NULL), m_value(0) {}
Chris@16:     generator_iterator(Generator* g) : m_g(g), m_value((*m_g)()) {}
Chris@16: 
Chris@16:     void increment()
Chris@16:     {
Chris@16:         m_value = (*m_g)();
Chris@16:     }
Chris@16: 
Chris@16:     const typename Generator::result_type&
Chris@16:     dereference() const
Chris@16:     {
Chris@16:         return m_value;
Chris@16:     }
Chris@16: 
Chris@16:     bool equal(generator_iterator const& y) const
Chris@16:     {
Chris@16:         return this->m_g == y.m_g && this->m_value == y.m_value;
Chris@16:     }
Chris@16: 
Chris@16:  private:
Chris@16:     Generator* m_g;
Chris@16:     typename Generator::result_type m_value;
Chris@16: };
Chris@16: 
Chris@16: // seed() seeds a random number generator with good seed values
Chris@16: 
Chris@16: template <typename UniformRandomNumberGenerator>
Chris@16: inline void seed(UniformRandomNumberGenerator& rng)
Chris@16: {
Chris@16:     seed_rng seed_gen;
Chris@16:     generator_iterator<seed_rng> begin(&seed_gen);
Chris@16:     generator_iterator<seed_rng> end;
Chris@16:     rng.seed(begin, end);
Chris@16: }
Chris@16: 
Chris@16: // random_device does not / can not be seeded
Chris@16: template <>
Chris@16: inline void seed<boost::random::random_device>(boost::random::random_device&) {}
Chris@16: 
Chris@16: // random_device does not / can not be seeded
Chris@16: template <>
Chris@16: inline void seed<seed_rng>(seed_rng&) {}
Chris@16: 
Chris@16: }}} //namespace boost::uuids::detail
Chris@16: 
Chris@16: #if defined(_MSC_VER)
Chris@16: #pragma warning(pop) // Restore warnings to previous state.
Chris@16: #endif
Chris@16: 
Chris@16: #endif