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utils/boost_idb/boost/uuid/random_generator.hpp

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+// Boost random_generator.hpp header file  ----------------------------------------------//
+
+// Copyright 2010 Andy Tompkins.
+// 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)
+
+#ifndef BOOST_UUID_RANDOM_GENERATOR_HPP
+#define BOOST_UUID_RANDOM_GENERATOR_HPP
+
+#include <boost/uuid/uuid.hpp>
+#include <boost/uuid/seed_rng.hpp>
+#include <boost/random/uniform_int.hpp>
+#include <boost/random/variate_generator.hpp>
+#include <boost/random/mersenne_twister.hpp>
+#include <boost/assert.hpp>
+#include <boost/shared_ptr.hpp>
+#include <limits>
+
+namespace boost {
+namespace uuids {
+
+// generate a random-based uuid
+template <typename UniformRandomNumberGenerator>
+class basic_random_generator {
+private:
+    typedef uniform_int<unsigned long> distribution_type;
+    typedef variate_generator<UniformRandomNumberGenerator*, distribution_type> generator_type;
+
+    struct null_deleter
+    {
+        void operator()(void const *) const {}
+    };
+
+public:
+    typedef uuid result_type;
+    
+    // default constructor creates the random number generator
+    basic_random_generator()
+        : pURNG(new UniformRandomNumberGenerator)
+        , generator
+          ( pURNG.get()
+          , distribution_type
+            ( (std::numeric_limits<unsigned long>::min)()
+            , (std::numeric_limits<unsigned long>::max)()
+            )
+          )
+    {
+        // seed the random number generator
+        detail::seed(*pURNG);
+    }
+    
+    // keep a reference to a random number generator
+    // don't seed a given random number generator
+    explicit basic_random_generator(UniformRandomNumberGenerator& gen)
+        : pURNG(&gen, null_deleter())
+        , generator
+          ( pURNG.get()
+          , distribution_type
+            ( (std::numeric_limits<unsigned long>::min)()
+            , (std::numeric_limits<unsigned long>::max)()
+            )
+          )
+    {}
+    
+    // keep a pointer to a random number generator
+    // don't seed a given random number generator
+    explicit basic_random_generator(UniformRandomNumberGenerator* pGen)
+        : pURNG(pGen, null_deleter())
+        , generator
+          ( pURNG.get()
+          , distribution_type
+            ( (std::numeric_limits<unsigned long>::min)()
+            , (std::numeric_limits<unsigned long>::max)()
+            )
+          )
+    {
+        BOOST_ASSERT(pURNG);
+    }
+    
+    uuid operator()()
+    {
+        uuid u;
+        
+        int i=0;
+        unsigned long random_value = generator();
+        for (uuid::iterator it=u.begin(); it!=u.end(); ++it, ++i) {
+            if (i==sizeof(unsigned long)) {
+                random_value = generator();
+                i = 0;
+            }
+
+			// static_cast gets rid of warnings of converting unsigned long to boost::uint8_t
+            *it = static_cast<uuid::value_type>((random_value >> (i*8)) & 0xFF);
+        }
+
+        // set variant
+        // must be 0b10xxxxxx
+        *(u.begin()+8) &= 0xBF;
+        *(u.begin()+8) |= 0x80;
+
+        // set version
+        // must be 0b0100xxxx
+        *(u.begin()+6) &= 0x4F; //0b01001111
+        *(u.begin()+6) |= 0x40; //0b01000000
+
+        return u;
+    }
+
+private:
+    shared_ptr<UniformRandomNumberGenerator> pURNG;
+    generator_type generator;
+};
+
+typedef basic_random_generator<mt19937> random_generator;
+
+}} // namespace boost::uuids
+
+#endif //BOOST_UUID_RANDOM_GENERATOR_HPP