#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

//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
	}

	inline unsigned int randomize()
	{
		unsigned int seed;
#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)
			seed^=counter;                //incremented value, possibly randomly initialized
			seed^=(unsigned int)&counter; //memory address
		}
		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;
	}
};