Cycle shift with bitwise operators, help pls

Hello,

I'm writing a function which performs a cyclic shift on the bits of an unsigned character with bitwise operators.

For example: my variable is 128, so the bits are 1000 0000, if I cycle 2 then I get 0000 0010.

It works, my output is fine and everything, but I get an error message: 'stack around the variable number is corrupt'.

I think it has something to do with the fact that I add an integer to an unsigned char, but how do I correct it? Atoi doesn't work.

Post your code.

Oh yes, forgot it.

Code:

---

/* AUTH: Kevin Strijbos  DATE: 02/02/2012
  DESC: excercise 12.4 */


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


void cycle_shift (unsigned char *number, int n);


int main (void)
{
        unsigned char number;
        int n;


        printf("Enter a number: ");
        scanf("%d", &number);
        printf("How many positions do you want to shift: ");
        scanf("%d", &n);


        cycle_shift(&number, n);
        printf("SHIFTED: %d\n", number);


        return 0;
}


/* perfoms a cyclic shift */
void cycle_shift (unsigned char *number, int n)
{
        unsigned char LBIT = 0x80;
        unsigned char RBIT = 0x01;
        int counter;


        if (n >= 0)
        {
                /* left shift */
                for (counter = 0; counter < n ;counter++)
                {
                        if (LBIT & *number)
                        {
                                *number <<= 1;
                                *number += 1;
                        }
                        else
                                *number <<= 1;
                }
        }
        else
        {
                /* right shift */
                for (counter = 0; counter < n ;counter++)
                {
                        if (RBIT & *number)
                        {
                                *number >>= 1;
                                *number += 128;
                        }
                        else
                                *number >>= 1;
                }
        }
}

---

Perhaps the problem lies here:

Code:

---

scanf("%d", &number);

---

You could try using:

Code:

---

unsigned int input;
scanf("%u", &input);
number = (unsigned char)input;

---

and see if it makes a difference.

By the way, I think your right shift is broken because counter < n is always false since n < 0.

Oh indeed, didn't test that part and copied it quickly from my left shift.

And it works that way indeed, thanks for the help!