Quick sorting in C

This is the implementation of quick sort algorithm in C.

#include <stdio.h>
#include "algutils.h"

template<class T>
void qsort(T* a, long len)
{
    printf("call\n");
    long l = 0, r = len, mid = len/2;
    T temp, p;

    p = a[mid]; // central item

    /* Swap: items less than p will go to left, above - to right,
       l going from the left, r - from the right, before the item,
       which denies this rule. After finding of such items we will
       swap them
    do {
        // looking for item from the left which > p
        while (a[l] < p) l++;
        // looking for item from the right < p
        while (a[r] > p) r--;

        // swap them if no wrapping
        if (l <= r) {
            SWAP(a[l], a[r], temp);
            l++; r--; // go to next - without it - hang up!
        }
    } while (l<=r); // XXX may be better is l<r ?


    /* Recursive calls if there is what to sort.
    Both cases works, upper makes about 2 times lesser calls!
    Split by the point where on left side are all < p, on right:
    all > p. If to choice another point of splitting, result
    of pre-sorting will be lost - ordering on one of the sides
    will be denied
    */
    if (r > 0) qsort(a, r);
    if (len > l) qsort(a+l, len-l);

    /*if (len>1) {
        qsort(a, mid);
        qsort(a + mid, len - mid);
    }*/
}


/*****************************************
                   main
 ****************************************/
int main(void)
{
    int arr[] = {10, 9, 4, 5, 11, 45, 6, 7, 88, 1, 0, 1};
    PRINTARR(arr, "%d");
    qsort(arr, sizeofarray(arr));
    PRINTARR(arr, "%d");
    return (0);
}