| /* boost random/random_device.hpp header file |
| * |
| * Copyright Jens Maurer 2000 |
| * Copyright Steven Watanabe 2010-2011 |
| * Distributed under the Boost Software License, Version 1.0. (See |
| * accompanying file LICENSE_1_0.txt or copy at |
| * http://www.boost.org/LICENSE_1_0.txt) |
| * |
| * $Id: random_device.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $ |
| * |
| * Revision history |
| * 2000-02-18 Portability fixes (thanks to Beman Dawes) |
| */ |
| |
| // See http://www.boost.org/libs/random for documentation. |
| |
| |
| #ifndef BOOST_RANDOM_RANDOM_DEVICE_HPP |
| #define BOOST_RANDOM_RANDOM_DEVICE_HPP |
| |
| #include <string> |
| #include <boost/config.hpp> |
| #include <boost/noncopyable.hpp> |
| #include <boost/random/detail/auto_link.hpp> |
| |
| namespace boost { |
| namespace random { |
| |
| /** |
| * Class \random_device models a \nondeterministic_random_number_generator. |
| * It uses one or more implementation-defined stochastic processes to |
| * generate a sequence of uniformly distributed non-deterministic random |
| * numbers. For those environments where a non-deterministic random number |
| * generator is not available, class random_device must not be implemented. See |
| * |
| * @blockquote |
| * "Randomness Recommendations for Security", D. Eastlake, S. Crocker, |
| * J. Schiller, Network Working Group, RFC 1750, December 1994 |
| * @endblockquote |
| * |
| * for further discussions. |
| * |
| * @xmlnote |
| * Some operating systems abstract the computer hardware enough |
| * to make it difficult to non-intrusively monitor stochastic processes. |
| * However, several do provide a special device for exactly this purpose. |
| * It seems to be impossible to emulate the functionality using Standard |
| * C++ only, so users should be aware that this class may not be available |
| * on all platforms. |
| * @endxmlnote |
| * |
| * <b>Implementation Note for Linux</b> |
| * |
| * On the Linux operating system, token is interpreted as a filesystem |
| * path. It is assumed that this path denotes an operating system |
| * pseudo-device which generates a stream of non-deterministic random |
| * numbers. The pseudo-device should never signal an error or end-of-file. |
| * Otherwise, @c std::ios_base::failure is thrown. By default, |
| * \random_device uses the /dev/urandom pseudo-device to retrieve |
| * the random numbers. Another option would be to specify the /dev/random |
| * pseudo-device, which blocks on reads if the entropy pool has no more |
| * random bits available. |
| * |
| * <b>Implementation Note for Windows</b> |
| * |
| * On the Windows operating system, token is interpreted as the name |
| * of a cryptographic service provider. By default \random_device uses |
| * MS_DEF_PROV. |
| * |
| * <b>Performance</b> |
| * |
| * The test program <a href="\boost/libs/random/performance/nondet_random_speed.cpp"> |
| * nondet_random_speed.cpp</a> measures the execution times of the |
| * random_device.hpp implementation of the above algorithms in a tight |
| * loop. The performance has been evaluated on an |
| * Intel(R) Core(TM) i7 CPU Q 840 \@ 1.87GHz, 1867 Mhz with |
| * Visual C++ 2010, Microsoft Windows 7 Professional and with gcc 4.4.5, |
| * Ubuntu Linux 2.6.35-25-generic. |
| * |
| * <table cols="2"> |
| * <tr><th>Platform</th><th>time per invocation [microseconds]</th></tr> |
| * <tr><td> Windows </td><td>2.9</td></tr> |
| * <tr><td> Linux </td><td>1.7</td></tr> |
| * </table> |
| * |
| * The measurement error is estimated at +/- 1 usec. |
| */ |
| class random_device : private noncopyable |
| { |
| public: |
| typedef unsigned int result_type; |
| BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
| |
| /** Returns the smallest value that the \random_device can produce. */ |
| static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return 0; } |
| /** Returns the largest value that the \random_device can produce. */ |
| static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return ~0u; } |
| |
| /** Constructs a @c random_device, optionally using the default device. */ |
| BOOST_RANDOM_DECL random_device(); |
| /** |
| * Constructs a @c random_device, optionally using the given token as an |
| * access specification (for example, a URL) to some implementation-defined |
| * service for monitoring a stochastic process. |
| */ |
| BOOST_RANDOM_DECL explicit random_device(const std::string& token); |
| |
| BOOST_RANDOM_DECL ~random_device(); |
| |
| /** |
| * Returns: An entropy estimate for the random numbers returned by |
| * operator(), in the range min() to log2( max()+1). A deterministic |
| * random number generator (e.g. a pseudo-random number engine) |
| * has entropy 0. |
| * |
| * Throws: Nothing. |
| */ |
| BOOST_RANDOM_DECL double entropy() const; |
| /** Returns a random value in the range [min, max]. */ |
| BOOST_RANDOM_DECL unsigned int operator()(); |
| |
| /** Fills a range with random 32-bit values. */ |
| template<class Iter> |
| void generate(Iter begin, Iter end) |
| { |
| for(; begin != end; ++begin) { |
| *begin = (*this)(); |
| } |
| } |
| |
| private: |
| class impl; |
| impl * pimpl; |
| }; |
| |
| } // namespace random |
| |
| using random::random_device; |
| |
| } // namespace boost |
| |
| #endif /* BOOST_RANDOM_RANDOM_DEVICE_HPP */ |