io_speed_buffer.c

#include <stdio.h>
#include <unistd.h>
#include <sys/times.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>

#define MAX_PUFFER_GROESSE 1<<14
// Ausgabe
static void zeit_ausgabe(long int puff_groesse, clock_t realzeit, struct tms *start_zeit, struct tms *ende_zeit, long int schleiflaeufe);

int main(void) {
    char puffer[MAX_PUFFER_GROESSE];
    ssize_t n;
    long int i, j=0, puffer_groesse, opt_puffer;
    struct tms start_zeit, ende_zeit;
    static long ticks=0;
    clock_t uhr_start, uhr_ende, system_cpu=0.0;

    // Ausgabe
    fprintf(stderr, "+--------------+-------------+--------------+--------------+--------------+\n");
    fprintf(stderr, "| %-10s | %-10s | %-10s | %-10s | %-10s |\n",
                    "Puffer-", "UserCPU", "SystemCPU", "Gebrauchte", "Schleifen-");
    fprintf(stderr, "| %10s | %10s | %10s | %10s | %10s |\n",
                    " groesse", " (Sek)", " (Sek)", " Uhrzeit", " laeufe");
    fprintf(stderr, "+--------------+-------------+--------------+--------------+--------------+\n");

    while (j <= 14) {
        i=0;
        puffer_groesse=1<<j;
        if (lseek(STDIN_FILENO, 0L, SEEK_SET) == -1) {
            fprintf(stderr, "Error: lseek");
            exit(1);
        }
        if (lseek(STDOUT_FILENO, 0L, SEEK_SET) == -1) {
            fprintf(stderr, "Errir: lseek");
            exit(1);
        }
        if ( (uhr_start = times(&start_zeit)) == -1) {
            fprintf(stderr, "Error: times");
            exit(2);
        }
        while ( (n=read(STDIN_FILENO, puffer, puffer_groesse)) > 0) {
            if (write(STDOUT_FILENO, puffer, n) != n) {
                fprintf(stderr, "Error: write");
                exit(3);
            }
            i++;
        }
        if (n < 0) {
            fprintf(stderr, "Error: read");
            exit(4);
        }
        if ( (uhr_ende = times(&ende_zeit)) == -1) {
            fprintf(stderr, "Error: times");
            exit(5);
        }

        if (ticks == 0) {
            if ( (ticks = sysconf(_SC_CLK_TCK)) < 0) {
                fprintf(stderr, "Error: sysconf");
                exit(6);
            }
        }
        // Ausgabe
        zeit_ausgabe(puffer_groesse, uhr_ende-uhr_start, &start_zeit, &ende_zeit, i);
        j++;
    }
    exit(0);
}

// Ausgabe
static void zeit_ausgabe(long int puff_groesse, clock_t realzeit, struct tms *start_zeit, struct tms *ende_zeit, long int schleiflaeufe) {
    static long ticks=0;
    if (ticks == 0) {
        if ( (ticks = sysconf(_SC_CLK_TCK)) < 0) {
            fprintf(stderr, "Error: sysconf");
            exit(6);
        }
    }
    fprintf(stderr, "| %10ld | %10.2f | %10.2f | %10.2f | %10ld |\n", puff_groesse, (ende_zeit->tms_utime - start_zeit->tms_utime) / (double)ticks, (ende_zeit->tms_stime - start_zeit->tms_stime) / (double)ticks, realzeit / (double)ticks, schleiflaeufe);
    return;
}