client.c

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

#define FIB_DEV "/dev/fibonacci"

int main(int argc, char *argv[])
{
    int fd, fd_out;
    long long sz;

    clockid_t cid = 1;
    struct timespec start, end;

    char write_buf[] = "testing writing";
    int offset = 100;
    int i = 0;

    fd = open(FIB_DEV, O_RDWR);
    fd_out = open(argv[1], O_RDWR | O_CREAT | O_TRUNC, 644);

    if (fd < 0) {
        perror("Failed to open character device");
        exit(1);
    }

    for (i = 0; i <= offset; i++) {
        sz = write(fd, write_buf, strlen(write_buf));
        printf("Writing to " FIB_DEV ", returned the sequence %lld\n", sz);
    }

    char buffer[300];
    char kbuffer[300];
    for (i = 0; i <= offset; i++) {
        lseek(fd, i, SEEK_SET);

        clock_gettime(cid, &start);
        sz = read(fd, kbuffer, 50);

        clock_gettime(cid, &end);
        long int sec, nanosec;
        sec = end.tv_sec - start.tv_sec;
        nanosec = end.tv_nsec - start.tv_nsec;

        char time[8];
        memcpy(time, kbuffer, 8);
        snprintf(buffer, 300, "%d %ld %ld\n", i, sec * 1000000000 + nanosec,
                 atol(time));
        write(fd_out, buffer, strlen(buffer));
        printf("Reading from " FIB_DEV " at offset %d, returned the sequence ",
               i);

        int j = 0;
        while (1) {
            if (kbuffer[8 + j] == 0) {
                break;
            }
            printf("%c", kbuffer[8 + j]);
            j++;
        }

        printf(".\n");
    }

    for (i = offset; i >= 0; i--) {
        lseek(fd, i, SEEK_SET);
        sz = read(fd, kbuffer, 50);
        printf("Reading from " FIB_DEV " at offset %d, returned the sequence ",
               i);
        int j = 0;
        while (1) {
            if (kbuffer[8 + j] == 0) {
                break;
            }
            printf("%c", kbuffer[8 + j]);
            j++;
        }

        printf(".\n");
    }

    close(fd);
    close(fd_out);
    return 0;
}