CanonicalTransactionChain.sol

/**
 * @title CanonicalTransactionChain
 * @dev The Canonical Transaction Chain (CTC) contract is an append-only log of transactions
 * which must be applied to the rollup state. It defines the ordering of rollup transactions by
 * writing them to the 'CTC:batches' instance of the Chain Storage Container.
 * The CTC also allows any account to 'enqueue' an L2 transaction, which will require that the
 * Sequencer will eventually append it to the rollup state.
 *
 */
contract CanonicalTransactionChain is ICanonicalTransactionChain, Lib_AddressResolver {
    /**
     * Inserts a batch into the chain of batches.
     * @param _transactionRoot Root of the transaction tree for this batch.
     * @param _batchSize Number of elements in the batch.
     * @param _numQueuedTransactions Number of queue transactions in the batch.
     * @param _timestamp The latest batch timestamp.
     * @param _blockNumber The latest batch blockNumber.
     */
    function _appendBatch(
        bytes32 _transactionRoot,
        uint256 _batchSize,
        uint256 _numQueuedTransactions,
        uint40 _timestamp,
        uint40 _blockNumber
    ) internal {
        IChainStorageContainer batchesRef = batches();
        (uint40 totalElements, uint40 nextQueueIndex, , ) = _getBatchExtraData();

        Lib_OVMCodec.ChainBatchHeader memory header = Lib_OVMCodec.ChainBatchHeader({
            batchIndex: batchesRef.length(),
            batchRoot: _transactionRoot,
            batchSize: _batchSize,
            prevTotalElements: totalElements,
            extraData: hex""
        });

        emit TransactionBatchAppended(
            header.batchIndex,
            header.batchRoot,
            header.batchSize,
            header.prevTotalElements,
            header.extraData
        );

        bytes32 batchHeaderHash = Lib_OVMCodec.hashBatchHeader(header);
        bytes27 latestBatchContext = _makeBatchExtraData(
            totalElements + uint40(header.batchSize),
            nextQueueIndex + uint40(_numQueuedTransactions),
            _timestamp,
            _blockNumber
        );

        // slither-disable-next-line reentrancy-no-eth, reentrancy-events
        batchesRef.push(batchHeaderHash, latestBatchContext);
    }
}