comparison DEPENDENCIES/generic/include/boost/random/random_device.hpp @ 16:2665513ce2d3

Add boost headers

+/* 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 */