Inserting an element into a sorted array

bin_insertion.c

int binpos(int *,int,int,int);
int insert(int *,int,int);

int binpos(int *a,int low,int high,int key)
{
	int mid=0;
    while(high>=low)
    {
        mid=(low+high)/2;
        if(a[mid]==key)
            return mid;
        else if(a[mid]>key)
            high=mid-1;
        else
            low=mid+1;
	}
    return mid;
}

int insert(int a[],int r,int key)
{
	int pos=binpos(a,0,r,key),i=0;
	r++;
	if(key<a[pos])
		for(i=r;i>pos;i--)
			a[i]=a[i-1];
	else
		for(i=r;i>pos+1;i--)
			a[i]=a[i-1];
	a[i]=key;
	return r;
}

Give the current array,highest index and new element as input, it returns the new index after inserting the element into the array,
if array is null then highest index is -1