In-place array rotation

The idea that is commonly seen in skill testing interview questions is using three reversals to perform the rotations: rev(1,k) rev(k+1,n-k) rev(1,n). This leads us to the following code:

int reverse(struct baseType * a, int n) { 
    int i, j; 
    j = n / 2;
    n--;
    for (i=0; i < j; i++) { 
        struct baseType tmp = a[i]; 
        a[i] = a[n-i];
        a[n-i] = tmp;
    }
    return 0;
}

int rotate(struct baseType a[], int n, int k) { 
    if(a == NULL || n <= 0) 
       return -__LINE__;
    if(k < 0 || k >= n){ 
       k %= n; 
       if (k < 0) k += n; 
    }
    if (k == 0) return 0;
    reverse (a, k);
    reverse (a + k, n - k);
    reverse (a, n);
    return 0;
 }

This solution reads and writes each element twice, however, some quick performance testing on random arrays shows that this code is faster for very small sized baseTypes. The reason being that the reverse() is very good for memory access locality. However, for any larger sized baseTypes, the first code sequence given will win by the simple virtue of performing fewer operations.