I do not do a lot of programing but ...

Would really love some help on getting this working.

I was given the decrypt function and was trying to build the shell. I really don't remember my pointers and references, but think it is close...

Please help! - Thanks!

Code:

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#include <stdio.h>

void decrypt();

int main() {
char in[255] = "NpfTvZKQKlM8Jh19/vI";

decrypt(in);

}

int index(char *x) {
  char encIndex[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

// Not sure how to reference the array, but I believe I need to take in a char and return
// an int.

return 0;
}
void decrypt (char *in)
{
    char first, second, third, fourth;
    int lf_count = 0,
        i        = 0;
    int byte_count = strlen(in);
    while (byte_count > 0)
    {
        first  = index(&in[i]);
        second = index(&in[i + 1]);
        third  = index(&in[i + 2]);
        fourth = index(&in[i + 3]);

        if (byte_count > 2)
            first = (first << 2) | (second >> 4);
        else
            first = (first << 2);

        printf("%c", first);

        if (byte_count > 2)
        {
            if (byte_count > 3)
                second = (second << 4) | (third >> 2);
            else
                second = (second << 4);
        }

        printf("%c", second);

        if (byte_count > 3)
        {
            third = (third << 6) | fourth;
            printf("%c", third);
        }

        i += 4;
        byte_count -= 4;
        lf_count++;
    }
}

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Welcome to the boards - use CODE tags when pasting code. Like:
[code]-Your code-[/code]

> int index(char *x)

int index(char x)
first = index(in[ i ]);
Would seem a better interface.

Then in your index() function, use a for loop to compare each element of encIndex with the parameter.

Your encIndex array has gone out of bounds at size 64. The encrypted input is "NpfTvZKQKlM8Jh19/vI". So, what would be the expected decrypted output for this string?

A possible suggestion for the index function..

Code:

---

int index(char *x)
{
  char encIndex[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  // or char encIndex[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  return (int) (strchr(encIndex, *x)- encIndex);
 // Not sure how to reference the array, but I believe I need to take in a char and return
// an int.
}

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