C algorithms for Kolibri

#include <stdio.h>
#include <time.h>
#include <stdlib.h>

#define MSG_LENGTH 64

int find_length(char* line) {
    int i = 0;
    for (;;) {
        if (line[i] == 0) break;
        i++;
    }
    return i;
}

void rotate_line(char* in, char* out) {
    int i, j, l;
    l = find_length(in);
    if (l == 0) return;
    i = l - 1;
    j = 0;
    for (;;) {
        out[j] = in[i];
        j++;
        if (i == 0) break;
        i--;
    }
}

void fill_line(char* in) {
    int i;
    i = find_length(in);
    for (;;) {
        if (i == MSG_LENGTH) break;
        in[i] = 32 + rand()%95;
        i++;
    }
}

void copy_line(char* in, char* out) {
    int i;
    i = 0;
    for (;;) {
        if (i == MSG_LENGTH) break;
        out[i] = in[i];
        i++;
    }
}

void shift_left(char* in, char* out, int shft) {
    int i, j;
    j = 0;
    i = shft;
    for (;;) {
       if (i == MSG_LENGTH) break;
       out[j] = in[i];
       i++;
       j++;
    }
    i = 0;
    for (;;) {
       if (i == shft) break;
       out[j] = in[i];
       i++;
       j++;
    }
}

void shift_right(char* in, char* out, int shft) {
    int i, j;
    j = shft;
    i = 0;
    for (;;) {
       if (i == MSG_LENGTH-shft) break;
       out[j] = in[i];
       j++;
       i++;
    }
    j = 0;
    for (;;) {
       if (i == MSG_LENGTH) break;
       out[j] = in[i];
       j++;
       i++;
    }
}

void clear_line(char* in) {
    int i;
    i = 0;
    for (;;) {
        if (i == MSG_LENGTH+1) break;
        in[i] = 0;
        i++;
    }
}

void erase_enters(char* in) {
    int i;
    i = 0;
    for (;;) {
        if (i == MSG_LENGTH+1) break;
        if (in[i] == 0x0a) in[i]=0x0;
        i++;
    }
}

int sum_chars(char* in) {
    int i, s;
    i = 0;
    s = 0;
    for (;;) {
        if (i == MSG_LENGTH) break;
        s = s + in[i];
        i++;
    }
    return s;
}

int main(int argc, char *argv[]) {

    srand(time(NULL));   // should only be called once

    int i, j, rot, shft, direction, sum;

    char msg[MSG_LENGTH+1];
    char tmp[MSG_LENGTH+1];

    clear_line(msg);
    clear_line(tmp);

    printf("Enter a line:\n");
    fgets(msg, MSG_LENGTH+1, stdin);
    erase_enters(msg);
    printf("Got a line:\n%s\nLength = %i\n", msg, find_length(msg));

    /* Fill Line */

    fill_line(msg);

    /* Sum of Chars */

    sum = sum_chars(msg);
    printf("Sum of chars = %i\n", sum);

    /* ??? ROTATE ??? */

    if (argc > 1)
        rot = ( atoi(argv[1]) ) % 2;
    else
        rot = ( rand() + sum ) % 2;

    if (rot == 1) {
        rotate_line(msg, tmp);
        copy_line(tmp, msg);
    }

    printf("Rotate = %i\n", rot);

    /* Print... */

    printf("Filled (and rotated?) line:\n%s\n", msg);
    printf("Last chars: 0x%08x, 0x%08x, 0x%08x\n",
            msg[MSG_LENGTH-2], msg[MSG_LENGTH-1], msg[MSG_LENGTH]);

    /* ??? SHIFT ??? */

    if (argc > 2)
        shft = ( atoi(argv[2]) ) % MSG_LENGTH;
    else
        shft = ( rand() + sum ) % MSG_LENGTH;

    printf("Shift = %i\n", shft);

    /* ??? DIRECTION ??? */

    if (argc > 3)
        direction = ( atoi(argv[3]) ) % 2;
    else
        direction = ( rand() + sum ) % 2;

    printf("Direction = %i\n", direction);

    /* SHIFTING... */

    if (direction == 0)
        shift_left(msg, tmp, shft);
    else
        shift_right(msg, tmp, shft);

    copy_line(tmp, msg);

    printf("Shifted line:\n%s\n", msg);

    /* ... */

    printf("Last chars: 0x%08x, 0x%08x, 0x%08x\n",
            msg[MSG_LENGTH-2], msg[MSG_LENGTH-1], msg[MSG_LENGTH]);

    return 0;
}