mergesort.c

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

static int mergesort_(void *base,const size_t num,const size_t size
     ,int (*compare)(const void *,const void *),int *temp)
{
	size_t counter_a = 0,counter_b = 0;
	if(size != 1){
		mergesort_(array,size>>1,temp);
		mergesort_(&array[size>>1],size-(size>>1),temp);
		while(counter_a != size>>1 && (size>>1)+counter_b != size){
			if(array[counter_a] <= array[(size>>1)+counter_b]){
				temp[counter_a+counter_b] = array[counter_a];
				counter_a++;
			}
			else{
				temp[counter_a+counter_b] = array[(size>>1)+counter_b];
				counter_b++;
			}
		}
		if(counter_a != size>>1){
			memcpy(&array[counter_a+counter_b],&array[counter_a]
			    ,sizeof(int)*(size-counter_a-counter_b));
		}
		memcpy(array,temp,sizeof(int)*(counter_a+counter_b));
	}
}

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

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

int main(void)
{
	int array[10] = {6,6,1,4,2,9,3,7,10,8};
	size_t counter = 0;
	mergesort(array,10,sizeof(int),compare_integer);
	while(counter != 10){
		printf("%d ",array[counter]);
		counter++;
	}
	return 0;
}