static void BN_POOL_release(BN_POOL *p, unsigned int num)
	{
	unsigned int offset = (p->used - 1) % BN_CTX_POOL_SIZE;
	p->used -= num;
	while(num--)
		{
		bn_check_top(p->current->vals + offset);
		if(!offset)
			{
			offset = BN_CTX_POOL_SIZE - 1;
			p->current = p->current->prev;
			}
		else
			offset--;
		}
	}