Cleanups.

[TD_C.git] / TP_7_C / exo3-extra.c

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

int stringLength(const char* str) {
    int result = 0;

    for (; str[result]; ++result);

    return result;
}

void swap(char* v1, char* v2) {
    char temp = *v1;
    *v1 = *v2;
    *v2 = temp;
}

void reverseString(char* str) {
    char* begin = str;
    char* end = str + stringLength(str) - 1;

    while (begin < end) {
        swap(begin++, end--);
    }
}

/** Perform a classical ROT13 permutation in-place */
void rot13(char* str) {
    char* cursor = str;
    char* end = str + stringLength(str);

    while (cursor < end) {
        if (*cursor >= 'a' && *cursor <= 'z') {
            *cursor = (*cursor - 'a' + 13) % 26 + 'a';
        } else if (*cursor >= 'A' && *cursor <= 'Z') {
            *cursor = (*cursor - 'A' + 13) % 26 + 'A';
        }

        ++cursor;
    }
}

int main() {
    char* msg;
    puts("Enter your message:");
    int readValue = scanf("%ms", &msg);

    if (readValue == 0) {
        puts("oops");
        return 0;
    }

    printf("Initial value: \"%s\"\n", msg);
    reverseString(msg);
    printf("Reversed     : \"%s\"\n", msg);
    reverseString(msg); // Restore the original message
    rot13(msg);
    printf("ROT13        : \"%s\"\n", msg);
    free(msg); // scanf("%ms") allocate dynamic memory
}