/* 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 */ |