| /* boost nondet_random.hpp header file |
| * |
| * Copyright Jens Maurer 2000 |
| * 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: nondet_random.hpp 62347 2010-05-31 16:44:36Z steven_watanabe $ |
| * |
| * Revision history |
| * 2000-02-18 Portability fixes (thanks to Beman Dawes) |
| */ |
| |
| // See http://www.boost.org/libs/random for documentation. |
| |
| |
| #ifndef BOOST_NONDET_RANDOM_HPP |
| #define BOOST_NONDET_RANDOM_HPP |
| |
| #include <string> // std::abs |
| #include <algorithm> // std::min |
| #include <boost/config/no_tr1/cmath.hpp> |
| #include <boost/config.hpp> |
| #include <boost/utility.hpp> // noncopyable |
| #include <boost/integer_traits.hpp> // compile-time integral limits |
| #include <boost/random/detail/auto_link.hpp> |
| |
| namespace boost { |
| |
| /** |
| * 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 |
| * nondet_random.hpp implementation of the above algorithms in a tight |
| * loop. The performance has been evaluated on a Pentium Pro 200 MHz |
| * with gcc 2.95.2, Linux 2.2.13, glibc 2.1.2. |
| * |
| * <table cols="2"> |
| * <tr><th>class</th><th>time per invocation [usec]</th></tr> |
| * <tr><td> @xmlonly <classname alt="boost::random_device">random_device</classname> @endxmlonly </td><td>92.0</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 = true); |
| BOOST_STATIC_CONSTANT(result_type, min_value = integer_traits<result_type>::const_min); |
| BOOST_STATIC_CONSTANT(result_type, max_value = integer_traits<result_type>::const_max); |
| |
| /** |
| * Returns: The smallest value that the \random_device can produce. |
| */ |
| result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return min_value; } |
| /** |
| * Returns: The largest value that the \random_device can produce. |
| */ |
| result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return max_value; } |
| /** |
| * 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 = default_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()(); |
| |
| private: |
| BOOST_RANDOM_DECL static const char * const default_token; |
| |
| /* |
| * std:5.3.5/5 [expr.delete]: "If the object being deleted has incomplete |
| * class type at the point of deletion and the complete class has a |
| * non-trivial destructor [...], the behavior is undefined". |
| * This disallows the use of scoped_ptr<> with pimpl-like classes |
| * having a non-trivial destructor. |
| */ |
| class impl; |
| impl * pimpl; |
| }; |
| |
| |
| // TODO: put Schneier's Yarrow-160 algorithm here. |
| |
| } // namespace boost |
| |
| #endif /* BOOST_NONDET_RANDOM_HPP */ |