/* gcc noise.c -o noise -lm */

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/time.h>
#include <time.h>
#include <string.h>

#define error(msg) { fprintf(stderr, msg); fflush(stderr); _exit(1); }
#define lhrandom(MIN,MAX) (((double)rand() / RAND_MAX) * ((MAX)-(MIN)) + (MIN))
#define clamp(VAL,MIN,MAX) ((VAL)>(MAX) ? (MAX) : (VAL) < (MIN) ? (MIN) : (VAL))

double sys_get_time (void)
{
    struct timeval t;
    gettimeofday(&t, 0);
    return (double)t.tv_sec + ((double)t.tv_usec)/1000000.0;
}

#define SCALE 24
#define BLAST 5.5

int main (void)
{
    int f = open("/dev/dsp", O_WRONLY);

    if (f < 0)
        error("Failed to open /dev/dsp for writing\n");

    srand(time(NULL));

    while (1)
    {
        uint i;
        unsigned char b[SCALE];
        double t = sys_get_time()*BLAST;
        static unsigned char c = 0, inc = 1, c2 = 0;
        static int k = 2;

        memset(b, 0, sizeof(b));

        if (c)
        {
            for (i = 0; i < sizeof(b) ;i+=k)
                b[i] = (inc+1)*sin(t)*100 + lhrandom(0, k*100);

            c = 0;
        }
        else
        {
            for (i = 0; i < sizeof(b) ;i+=k + inc - 1)
                b[i] = k + cos(t)*k*5 + lhrandom(-32*inc, 32);

            c = 1;
        }

        if (inc)
        {
            if (++k > 64)
            {
                inc = 0;
                k = 64;
            }
        }
        else
        {
            if (--k < 2)
                inc = k = 2;
        }

        if (k == 64)
        {
            c2++;
            if (c2 > 3)
                c2 = 0;
        }

        if (sin(t/k) > 0.9 || BLAST*sin(t*4) > 0.8)
        {
            for (i = 0; i < SCALE ;i+=1+(k&9)+c2)
                if (c)
                    b[i] |= ~(int)(64*k*(inc ? cos(t*5) : sin(t*3)) + lhrandom(-100, 100));
                else
                    b[i] |=  (int)(64*k*(inc ? cos(t*5) : sin(t*3)) + lhrandom(-100, 100));
        }

        write(f, b, sizeof(b));
        write(f, b + sizeof(b)/2 + k/3, sizeof(b)/2 - sizeof(b)/(1+inc));
    }

    close(f);

    return 0;
}