| 1669 | } |
| 1670 | |
| 1671 | void PositiveSubtract(Integer &diff, const Integer &a, const Integer& b) |
| 1672 | { |
| 1673 | unsigned aSize = a.WordCount(); |
| 1674 | aSize += aSize%2; |
| 1675 | unsigned bSize = b.WordCount(); |
| 1676 | bSize += bSize%2; |
| 1677 | |
| 1678 | if (aSize == bSize) |
| 1679 | { |
| 1680 | if (Compare(a.reg, b.reg, aSize) >= 0) |
| 1681 | { |
| 1682 | Subtract(diff.reg, a.reg, b.reg, aSize); |
| 1683 | diff.sign = Integer::POSITIVE; |
| 1684 | } |
| 1685 | else |
| 1686 | { |
| 1687 | Subtract(diff.reg, b.reg, a.reg, aSize); |
| 1688 | diff.sign = Integer::NEGATIVE; |
| 1689 | } |
| 1690 | } |
| 1691 | else if (aSize > bSize) |
| 1692 | { |
| 1693 | word borrow = Subtract(diff.reg, a.reg, b.reg, bSize); |
| 1694 | CopyWords(diff.reg+bSize, a.reg+bSize, aSize-bSize); |
| 1695 | borrow = Decrement(diff.reg+bSize, aSize-bSize, borrow); |
| 1696 | assert(!borrow); |
| 1697 | diff.sign = Integer::POSITIVE; |
| 1698 | } |
| 1699 | else |
| 1700 | { |
| 1701 | word borrow = Subtract(diff.reg, b.reg, a.reg, aSize); |
| 1702 | CopyWords(diff.reg+aSize, b.reg+aSize, bSize-aSize); |
| 1703 | borrow = Decrement(diff.reg+aSize, bSize-aSize, borrow); |
| 1704 | assert(!borrow); |
| 1705 | diff.sign = Integer::NEGATIVE; |
| 1706 | } |
| 1707 | } |
| 1708 | |
| 1709 | Integer operator+(const Integer &a, const Integer& b) |
| 1710 | { |