/*****************************************************************
Program:        randstp.c

    Generates random steps from a series of random numbers.
 
*****************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#define IBSIZ 1200000
#define OBSIZ 1000

int
main(argc, argv)
int  argc;
char *argv[];
{
char ifn[100], ofn[100];
FILE *ifd, *ofd;
char ibuf[IBSIZ];          /* Input Data Buffer    */
float obuf[OBSIZ];         /* Output Data Buffer   */
double ampli, period, sampint, srate;
float ratio;
int tfac, i, j, cnt1, n, N;
int incnt, outcnt, npad, datasize;
char  *pc;
short *ps;
long  *pl;

    pc = ibuf;
    ps = (short *) ibuf;
    pl = (long  *) ibuf;

    printf("%s", "Enter name of file containing the random numbers: ");
    scanf("%s", ifn);

	datasize = 2;
	ifd = fopen(ifn,"r");
	n = 150372;

    fread(ibuf, datasize, n, ifd);
    for (i = 0; i < n; i++) {
        if      (datasize == 1 && *pc++ == 0) break;
        else if (datasize == 2 && *ps++ == 0) break;
        else if (datasize == 4 && *pl++ == 0) break;
    }
    n = i;

    printf(" '%s' contains %d values; enter number of ouput steps  ", ifn, n);
    scanf("%d", &incnt);
    if (incnt > n) {
        fprintf(stderr,"randstp: bad input value\n");
        exit(1);
    }

    ampli = 1.0;

    printf("%s", "Enter clock period, that is, the minimum duration between steps (secs, integer)  ");
    scanf("%lf", &period);

    printf("%s", "Enter sample rate of output series (Hz)  ");
    scanf("%lf", &srate);
    sampint = 1. / srate;
    if (sampint == 0) {
        fprintf(stderr,"randstp: bad sample interval\n");
        exit(1);
    }
    ratio = (period / sampint);
    tfac = (int)(period / sampint);
    if ((ratio - (float) tfac) != 0.0) {
	fprintf(stderr,"randstp: sampint must be a multiple of clock period. Exiting.\n");
	exit(1);
    }

    printf("%s", "Enter name of output file (floats)  ");
    scanf("%s", ofn);
    ofd = fopen(ofn, "w");

/* zeroes padded at beg */
    printf("%s", "Enter number of zeroes to pad at the beginning: ");
    scanf("%d", &npad);
    for (i = 0; i < OBSIZ; i++) obuf[i] = 0;
    outcnt = 0;
    N = npad / OBSIZ;
    for (i = 0; i < N; i++) fwrite(obuf, sizeof(float), OBSIZ, ofd);
    N = npad % OBSIZ;
    fwrite(obuf, sizeof(float), N, ofd);
    outcnt += npad;

/* now make steps */
    cnt1 = 1;
    ampli = -ampli;
    i = j = 0;
    pc = ibuf;
    ps = (short *) ibuf;
    pl = (long  *) ibuf;
    while (1) {
        if (--cnt1 <= 0) {
            if      (datasize == 1) cnt1 = *pc++ * tfac;
            else if (datasize == 2) cnt1 = *ps++ * tfac;
            else if (datasize == 4) cnt1 = *pl++ * tfac;
            ampli = -ampli;
            ++j;
        }
        if ( j > incnt ) {
            fwrite(obuf, sizeof(float), i, ofd);
            break;
        }
        ++outcnt;
        obuf[i] = ampli;
        if ( ++i >= OBSIZ ) {
            fwrite(obuf, sizeof(float), OBSIZ, ofd);
            i = 0;
        }
    }

/* zeroes padded at end */
    printf("Enter number of zeroes to pad at the end:  ");
    scanf("%d", &npad);
    for (i = 0; i < OBSIZ; i++) obuf[i] = 0;
    N = npad / OBSIZ;
    for (i = 0; i < N; i++) fwrite(obuf, sizeof(float), OBSIZ, ofd);
    N = npad % OBSIZ;
    fwrite(obuf, sizeof(float), N, ofd);
    outcnt += npad;

    printf(" file '%s' written, %d points.\n", ofn, outcnt);
    fclose(ofd);
    exit(0);
}