//
// eput - Display elapsed time since previous measurement.
//        Note: EPUT = Events Per Unit Time, i.e., frequency.
//
// - User supplies event scaling factor (default 1).
// - One millisecond resolution (15 ms PC clock granularity).
//
// 24 Mar 2008 /tvb
//

#include <stdio.h>
#include <stdlib.h>
#include <sys/timeb.h>

char *eput_file = "/tmp/eput.txt";

void main (int argc, char *argv[])
{
    FILE *f;
    double now, then, scale, et, eput;
    double time_stamp (void);
    char *why;

    // Get optional arguments.

    why = "since last call";
    if (argc > 1) {
        why = argv[1];
    }
    scale = 1.0;
    if (argc > 2) {
        scale = atof(argv[1]);
        why = argv[2];
    }

    // Get previous time stamp.

    then = 0;
    f = fopen(eput_file, "r");
    if (f != NULL) {
        fscanf(f, "%lf", &then);
        fclose(f);
    }

    // Store current time stamp.

    now = time_stamp();
    f = fopen(eput_file, "w");
    if (f != NULL) {
        fprintf(f, "%.3lf", now);
        fclose(f);
    }

    // Calculate elapsed time (time interval).

    et = now - then;

    // Calculate events per unit time (frequency).

    eput = (et != 0.0) ? 1.0 * scale / et : 0.0;

    // Display results.

    printf("%.3lf seconds, %.3lf Hz: %s\n", et, eput, why);
}

// Get millisecond resolution time stamp.

double time_stamp (void)
{
    struct _timeb tb;

    _ftime(&tb);
    return tb.time + (double)tb.millitm / 1e3;
}