Operations with UInt64

[dgarcia360]

1. Expected behavior and actual behavior.

UInt64 class does not allow operating with the value. To start, we could support add() and subtract() capabilities.

2. Steps to reproduce the problem (example)

Catapult transactions can be rolled back up to a certain amount of blocks. We say that every time there is a new block, the transaction receives a confirmation. The more confirmation transaction has, the fewer chances this is rolled-back.

To determine if we can consider a transaction as persistent, we need to compare the current blockchain height with the transaction blockchain height. Then, determine if the difference is higher than a certain number we consider good enough to consider the transactions as confirmed. This can be calculated as:

isTransactionPersistent = (currentBlockchainHeight - transactionHeight >= (confirmationsToConsiderTransacitionPersistent);`

Note that right now, it is only possible to do (currentBlockchainHeight - transactionHeight) if the height is small enough and does not overflow when calling height.compact().

[fboucquez]

Java moved from custom low/high UInt64 object to a more native BigInteger several months ago. All the operations and documentation are out of the box.

Should ts move to a more standard big int implementation? What's the best big int library for ts/js out there?

[dgarcia360]

@fboucquez As far as I know, there is no native long type in TypeScript. I assume that the original SDK devs created the UInt64 class following the adapter pattern to not depend too much on an external library and be able to replace it if necessary.

We are currently using long library https://www.npmjs.com/package/long underneath.

[fboucquez]

@dgarcia360 thanks!, Who is we? Which project? would be long good/small enough for ts sdk?

[dgarcia360]

We -> the nem2-sdk-typescript-javascript project (https://github.com/nemtech/nem2-sdk-typescript-javascript/blob/master/package.json#L65)

[fboucquez]

Ok, so why not just replacing UInt64 with Long? Is it only for the abstraction?

[fboucquez]

https://github.com/nemtech/nem2-sdk-typescript-javascript/blob/master/src/model/transaction/TransferTransaction.ts#L186 uses Long directly breaking the abstraction if you want to keep it. Should we add a compare op?

Something like

b.id.id.compare(b.id.id) instead of creating the Longs.