Optimism batch decoder

Decodes the calldata of a batcher transaction and returns the L2 transactions within it

Background

The transactions of a L2 rollup are batched together and submitted to a L1. The Batcher will submit these batches to a Batch Inbox Address on L1, which is an EOA and will save gas because no code will be executed. 0xFF00000000000000000000000000000000000010 is the Batch Inbox Address of Optimism on Ethereum. The calldata of each transaction to the Batch Inbox contains batches of L2 as an encoded and compressed hex string.

Installation

npm i @blocktorch/optimism-batch-decoder or yarn add @blocktorch/optimism-batch-decoder

Usage

decodeBatcherTransactionCalldata(calldata)

Decodes the L2 transactions from raw calldata

• calldata - the calldata of the transaction by a Batcher to the Batch Inbox Address on L1. You can get it from the transaction page on Etherscan (Input Data -> View Input As Original). For an example, check example-data/calldata.txt.

import { decodeBatcherTransactionCalldata } from '@blocktorch/optimism-batch-decoder'

const batcherTransaction = await decodeBatcherTransactionCalldata(calldata)

decodeBatcherTransaction(txHash, providerUrl)

Wrapper for decodeBatcherTransactionCalldata. Will fetch the calldata for you based on the transaction hash.

• txHash - hash of the L1 transaction to the Batch Inbox
• providerUrl - RPC provider URL that is used to fetch data about the transaction

testWithExampleData(path?)

Test function to decode example calldata. You can provide the path to example call data, but by default it looks for example-data/calldata.txt in the repository.

• path - path to your own calldata relative to the repository root.

BatcherTransaction

All of the functions will return a BatcherTransaction. It contains a version and its Frames. More about the batcher transaction format

Each Frame contains info about the Frame and its batches.

And each Batch contains a list of transactions and info about the Batch

Known issues

NB! SpanBatch decoding is unimplemented at the moment.

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