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

static void quicksort_(void *base,const size_t num,const size_t size
    ,void *temp,int (*compare)(const void *,const void *))
{
	size_t pivot = 0,first2last = 0,last2first = num-1;
	while(pivot+1 != num && !compare(base+size*pivot,base+size*(pivot+1))){
		pivot++;
	}
	if(pivot+1 == num){
		return;
	}
	if(0 > compare(base+size*pivot,base+size*(pivot+1))){
		pivot++;
	}
	while(first2last < last2first){
		while(0 < compare(base+size*pivot,base+size*first2last)
		    && first2last != num-1){
			first2last++;
		}
		while(0 >= compare(base+size*pivot,base+size*last2first)
		    && last2first){
			last2first--;
		}
		if(first2last < last2first){
			if(pivot == first2last || pivot == last2first){
				pivot = pivot^last2first^first2last;
			}
			memcpy(temp,base+size*first2last,size);
			memcpy(base+size*first2last,base+size*last2first,size);
			memcpy(base+size*last2first,temp,size);
		}
	}
	quicksort_(base,first2last,size,temp,compare);
	quicksort_(base+size*first2last,num-first2last,size,temp,compare);
}

int quicksort(void *base,const size_t num,const size_t size
    ,int (*compare)(const void *,const void *))
{
	void *temp = malloc(size);
	if(!temp){
		return -1;
	}
	quicksort_(base,num,size,temp,compare);
	free(temp);
	return 0;
}

int compare_integer(const void *a,const void *b)
{
	return *(int *)a-*(int *)b;
}

int main(void)
{
	int array[8] = {6,6,1,4,2,9,3,7};
	int errcode = quicksort(array,8,sizeof(int),compare_integer);
	size_t counter = 0;
	if(errcode < 0){
		fputs("Error!\n",stderr);
		return -1;
	}
	while(counter != 8){
		printf("%d ",array[counter]);
		counter++;
	}
	return 0;
}