#include <stdint.h>
#include <math.h>

/*
 *  This is a simple random number generator with good quality for audio purposes.
 *  It consists of two polycounters with opposite rotation direction and different
 *  periods. The periods are coprime, so the total period is the product of both.
 *
 *     -------------------------------------------------------------------------------------------------
 * +-> |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0|
 * |   -------------------------------------------------------------------------------------------------
 * |                                                                          |  |  |  |     |        |
 * |                                                                          +--+--+--+-XOR-+--------+
 * |                                                                                      |
 * +--------------------------------------------------------------------------------------+
 *
 *     -------------------------------------------------------------------------------------------------
 *     |31:30:29:28:27:26:25:24:23:22:21:20:19:18:17:16:15:14:13:12:11:10: 9: 8: 7: 6: 5: 4: 3: 2: 1: 0| <-+
 *     -------------------------------------------------------------------------------------------------   |
 *       |  |           |  |                                                                               |
 *       +--+----XOR----+--+                                                                               |
 *                |                                                                                        |
 *                +----------------------------------------------------------------------------------------+
 *
 *
 *  The first has an period of 3*5*17*257*65537, the second of 7*47*73*178481,
 *  which gives a period of 18.410.713.077.675.721.215. The result is the
 *  XORed values of both generators.
 */


static const unsigned char  Parity [256] = {  // parity
    0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
    1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
    1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
    0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
    1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,
    0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
    0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0,1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,
    1,0,0,1,0,1,1,0,0,1,1,0,1,0,0,1,0,1,1,0,1,0,0,1,1,0,0,1,0,1,1,0
};

static uint32_t  rnd_r1 = 1;
static uint32_t  rnd_r2 = 1;


void
set_seed ( uint32_t seed )
{
    rnd_r1 = seed != 0 ? seed : 1;              // 0 is a forbidden value which locks the generator
    rnd_r2 = 1;                                 // the are several (8389119) forbidden codes. 1 is not one of them
}


uint32_t
random_int ( void )
{
    uint32_t  t1, t2, t3, t4;

    t3   = t1 = rnd_r1; t4   = t2 = rnd_r2;     // Parity calculation is done via table lookup, this is also available
    t1  &= 0xF5;        t2 >>= 25;              // on CPUs without parity, can be implemented in C and avoid unpredictable
    t1   = Parity [t1]; t2  &= 0x63;            // jumps and slow rotate through the carry flag operations.
    t1 <<= 31;          t2   = Parity [t2];

    return (rnd_r1 = (t3 >> 1) | t1 ) ^ (rnd_r2 = (t4 + t4) | t2 );
}


double
Random_Equal ( double mult )                    // gives a equal distributed random number
{                                               // between -2^31*mult and +2^31*mult
    return mult * (int32_t) random_int ();
}


double
Random_Normal ( void )                          // gives a normal distributed random number
{
    return sqrt (-2. * log ( (random_int () + 1) * (1./4294967296.)) ) *
           cos  ( (2.*M_PI/4294967296.) * random_int () );
}


double
Random_Exponential ( double mult )
{
    return -log ( (1. + random_int ()) * (1./4294967296.) );
}


double
Random_Triangular ( double mult )
{
    return mult * ((double)(int32_t) random_int () + (double)(int32_t) random_int ());
}

/* end of random.c */