source: cpp/common/random.h @ 182

// This file is a part of the Framsticks GDK.
// Copyright (C) 2002-2014  Maciej Komosinski and Szymon Ulatowski.  See LICENSE.txt for details.
// Refer to http://www.framsticks.com/ for further information.

#include "nonstd.h" //LONGLONG
#include <time.h> //time()
#ifdef MULTITHREADED
 #include "threads.h"
#endif
#ifdef LINUX
 #include <unistd.h>
 #include <sys/stat.h>
 #include <fcntl.h>
#endif
#ifdef _WIN32
 #define _WINSOCKAPI_ //http://stackoverflow.com/questions/1372480/c-redefinition-header-files
 #include <rpc.h> //UUID
 #pragma comment(lib, "Rpcrt4.lib")
#endif

//adapted from
//http://en.wikipedia.org/wiki/Mersenne_twister#Pseudocode
//http://my.opera.com/metrallik/blog/2013/04/19/c-class-for-random-generation-with-mersenne-twister-method

class RandomGenerator
{
private:
        static const unsigned int length = 624;
        static const unsigned int bitMask_32 = 0xffffffff;
        static const unsigned int bitPow_31 = 1 << 31;
        static const unsigned int MAXVALUE = 0xffffffff;
        unsigned int counter; //only used in randomize(). uninitialized is OK
#ifdef MULTITHREADED
        pthread_mutex_t lock;
#endif
        unsigned int *mt;
        unsigned int idx;
public:

        RandomGenerator(unsigned int seed)
        {
#ifdef MULTITHREADED
                pthread_mutex_init(&lock, NULL);
#endif
                mt = new unsigned int[length];
                setSeed(seed);
        }

        inline void setSeed(unsigned int seed)
        {
#ifdef MULTITHREADED
                pthread_mutex_lock(&lock);
#endif
                idx = 0;
                mt[0] = seed;
                for (unsigned int i = 1; i < length; i++)
                        mt[i] = (1812433253 * (mt[i - 1] ^ (mt[i - 1] >> 30)) + i)&bitMask_32;
#ifdef MULTITHREADED
                pthread_mutex_unlock(&lock);
#endif
        }

        unsigned int randomize()
        {
                unsigned int seed;
                //for ms visual, could use http://msdn.microsoft.com/en-us/library/sxtz2fa8.aspx
#ifdef LINUX
                int fd=open("/dev/urandom",O_RDONLY);
                if (fd>=0)
                {
                        read(fd,&seed,sizeof(seed));
                        close(fd);
                }
                else
#endif
                {
                        counter++;
                        seed = time(NULL);              //time (seconds); could use hi-res timer but then we would depend on common/timer.h
                        seed ^= counter;                //incremented value, possibly randomly initialized
                        seed ^= (unsigned int)&counter; //memory address
                }
#ifdef _WIN32 //add more randomness from uuid
                UUID uuid;
                ::UuidCreate(&uuid);
                seed ^= uuid.Data1^uuid.Data2^uuid.Data3^uuid.Data4[0];
#endif
                setSeed(seed);
                return seed;
        }

        inline unsigned int getUint32()
        {
#ifdef MULTITHREADED
                pthread_mutex_lock(&lock);
#endif
                if (idx == 0) gen();
                unsigned int y = mt[idx];
                idx = (idx + 1) % length;
#ifdef MULTITHREADED
                pthread_mutex_unlock(&lock);
#endif
                y ^= y >> 11;
                y ^= (y << 7) & 2636928640U;
                y ^= (y << 15) & 4022730752U;
                y ^= y >> 18;
                return y;
        }

        inline double getDouble() // [0,1)
        {
                return double(getUint32()) / ((LONGLONG)(MAXVALUE)+1);
        }

        inline void gen()
        {
                for (unsigned int i = 0; i < length; i++)
                {
                        unsigned int y = (mt[i] & bitPow_31) + (mt[(i + 1) % length] & (bitPow_31 - 1));
                        mt[i] = mt[(i + 397) % length] ^ (y >> 1);
                        if (y % 2) mt[i] ^= 2567483615U;
                }
                return;
        }

        ~RandomGenerator()
        {
                delete[] mt;
        }
};