void bn_mul_recursive(BN_ULONG *r, BN_ULONG *a, BN_ULONG *b, int n2,
	     BN_ULONG *t)
	{
	int n=n2/2,c1,c2;
	unsigned int neg,zero;
	BN_ULONG ln,lo,*p;

#ifdef BN_COUNT
printf(" bn_mul_recursive %d * %d\n",n2,n2);
#endif
#ifdef BN_MUL_COMBA
/*	if (n2 == 4)
		{
		bn_mul_comba4(r,a,b);
		return;
		}
	else */ if (n2 == 8)
		{
		bn_mul_comba8(r,a,b);
		return; 
		}
#endif
	if (n2 < BN_MUL_RECURSIVE_SIZE_NORMAL)
		{
		/* This should not happen */
		bn_mul_normal(r,a,n2,b,n2);
		return;
		}
	/* r=(a[0]-a[1])*(b[1]-b[0]) */
	c1=bn_cmp_words(a,&(a[n]),n);
	c2=bn_cmp_words(&(b[n]),b,n);
	zero=neg=0;
	switch (c1*3+c2)
		{
	case -4:
		bn_sub_words(t,      &(a[n]),a,      n); /* - */
		bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
		break;
	case -3:
		zero=1;
		break;
	case -2:
		bn_sub_words(t,      &(a[n]),a,      n); /* - */
		bn_sub_words(&(t[n]),&(b[n]),b,      n); /* + */
		neg=1;
		break;
	case -1:
	case 0:
	case 1:
		zero=1;
		break;
	case 2:
		bn_sub_words(t,      a,      &(a[n]),n); /* + */
		bn_sub_words(&(t[n]),b,      &(b[n]),n); /* - */
		neg=1;
		break;
	case 3:
		zero=1;
		break;
	case 4:
		bn_sub_words(t,      a,      &(a[n]),n);
		bn_sub_words(&(t[n]),&(b[n]),b,      n);
		break;
		}

#ifdef BN_MUL_COMBA
	if (n == 4)
		{
		if (!zero)
			bn_mul_comba4(&(t[n2]),t,&(t[n]));
		else
			memset(&(t[n2]),0,8*sizeof(BN_ULONG));
		
		bn_mul_comba4(r,a,b);
		bn_mul_comba4(&(r[n2]),&(a[n]),&(b[n]));
		}
	else if (n == 8)
		{
		if (!zero)
			bn_mul_comba8(&(t[n2]),t,&(t[n]));
		else
			memset(&(t[n2]),0,16*sizeof(BN_ULONG));
		
		bn_mul_comba8(r,a,b);
		bn_mul_comba8(&(r[n2]),&(a[n]),&(b[n]));
		}
	else
#endif
		{
		p= &(t[n2*2]);
		if (!zero)
			bn_mul_recursive(&(t[n2]),t,&(t[n]),n,p);
		else
			memset(&(t[n2]),0,n2*sizeof(BN_ULONG));
		bn_mul_recursive(r,a,b,n,p);
		bn_mul_recursive(&(r[n2]),&(a[n]),&(b[n]),n,p);
		}

	/* t[32] holds (a[0]-a[1])*(b[1]-b[0]), c1 is the sign
	 * r[10] holds (a[0]*b[0])
	 * r[32] holds (b[1]*b[1])
	 */

	c1=(int)(bn_add_words(t,r,&(r[n2]),n2));

	if (neg) /* if t[32] is negative */
		{
		c1-=(int)(bn_sub_words(&(t[n2]),t,&(t[n2]),n2));
		}
	else
		{
		/* Might have a carry */
		c1+=(int)(bn_add_words(&(t[n2]),&(t[n2]),t,n2));
		}

	/* t[32] holds (a[0]-a[1])*(b[1]-b[0])+(a[0]*b[0])+(a[1]*b[1])
	 * r[10] holds (a[0]*b[0])
	 * r[32] holds (b[1]*b[1])
	 * c1 holds the carry bits
	 */
	c1+=(int)(bn_add_words(&(r[n]),&(r[n]),&(t[n2]),n2));
	if (c1)
		{
		p= &(r[n+n2]);
		lo= *p;
		ln=(lo+c1)&BN_MASK2;
		*p=ln;

		/* The overflow will stop before we over write
		 * words we should not overwrite */
		if (ln < (BN_ULONG)c1)
			{
			do	{
				p++;
				lo= *p;
				ln=(lo+1)&BN_MASK2;
				*p=ln;
				} while (ln == 0);
			}
		}
	}