number

createL1Message

handleMessageFromL1

l1Target

numberFromL1

_l1Target

setL1Target

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import {L1Contract} from "./L1Contract.sol";
import {ArbSys} from "@arbitrum/nitro-contracts/src/precompiles/ArbSys.sol";

/// @title L2Contract
/// @notice An example L2 contract that interacts with an L1 contract (sends & receives messages)
/// @author saucepoint
contract L2Contract {
    // A number set by an L1-to-L2 message
    uint256 public numberFromL1;

    // Address of the L1 contract, where messages will be sent and received
    address public l1Target;

    // Arbitrum precompile, used to send messages to L1
    ArbSys constant arbsys = ArbSys(address(0x0000000000000000000000000000000000000064));

    /// @notice Sends a message to the L1 contract (set a uint256)
    /// @param number The number to set on the L1 contract state
    function createL1Message(uint256 number) external {
        bytes memory data = abi.encodeWithSelector(L1Contract.handleMessageFromL2.selector, number);
        arbsys.sendTxToL1(l1Target, data);
    }

    /// @notice Handle a message from the L1 contract
    /// @dev TODO: Add a modifier to ensure that this function can only be called by the L1 contract
    /// @param number The number received from the L1 contract
    function handleMessageFromL1(uint256 number) external {
        // Do something with the number
        numberFromL1 = number;
    }

    /// @notice Sets the L1 contract address
    /// @param _l1Target The address of the L1 contract that will be sending messages to this contract
    function setL1Target(address _l1Target) external {
        l1Target = _l1Target;
    }
}


L2Contract

activeOutbox

allowedDelayedInboxList

inbox

allowedDelayedInboxes

allowedOutboxList

outbox

allowedOutboxes

delayedInboxAccs

delayedMessageCount

kind

sender

messageDataHash

enqueueDelayedMessage

dataHash

afterDelayedMessagesRead

prevMessageCount

newMessageCount

enqueueSequencerMessage

seqMessageIndex

beforeAcc

delayedAcc

value

data

executeCall

success

returnData

rollup_

initialize

rollup

sequencerInbox

sequencerInboxAccs

sequencerMessageCount

sequencerReportedSubMessageCount

enabled

setDelayedInbox

setOutbox

_sequencerInbox

setSequencerInbox

batchPoster

submitBatchSpendingReport

msgNum

BridgeCallTriggered

InboxToggle

messageIndex

beforeInboxAcc

baseFeeL1

timestamp

MessageDelivered

OutboxToggle

newSequencerInbox

SequencerInboxUpdated

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.6.9 <0.9.0;

import "./IOwnable.sol";

interface IBridge {
    event MessageDelivered(
        uint256 indexed messageIndex,
        bytes32 indexed beforeInboxAcc,
        address inbox,
        uint8 kind,
        address sender,
        bytes32 messageDataHash,
        uint256 baseFeeL1,
        uint64 timestamp
    );

    event BridgeCallTriggered(
        address indexed outbox,
        address indexed to,
        uint256 value,
        bytes data
    );

    event InboxToggle(address indexed inbox, bool enabled);

    event OutboxToggle(address indexed outbox, bool enabled);

    event SequencerInboxUpdated(address newSequencerInbox);

    function allowedDelayedInboxList(uint256) external returns (address);

    function allowedOutboxList(uint256) external returns (address);

    /// @dev Accumulator for delayed inbox messages; tail represents hash of the current state; each element represents the inclusion of a new message.
    function delayedInboxAccs(uint256) external view returns (bytes32);

    /// @dev Accumulator for sequencer inbox messages; tail represents hash of the current state; each element represents the inclusion of a new message.
    function sequencerInboxAccs(uint256) external view returns (bytes32);

    function rollup() external view returns (IOwnable);

    function sequencerInbox() external view returns (address);

    function activeOutbox() external view returns (address);

    function allowedDelayedInboxes(address inbox) external view returns (bool);

    function allowedOutboxes(address outbox) external view returns (bool);

    function sequencerReportedSubMessageCount() external view returns (uint256);

    /**
     * @dev Enqueue a message in the delayed inbox accumulator.
     *      These messages are later sequenced in the SequencerInbox, either
     *      by the sequencer as part of a normal batch, or by force inclusion.
     */
    function enqueueDelayedMessage(
        uint8 kind,
        address sender,
        bytes32 messageDataHash
    ) external payable returns (uint256);

    function executeCall(
        address to,
        uint256 value,
        bytes calldata data
    ) external returns (bool success, bytes memory returnData);

    function delayedMessageCount() external view returns (uint256);

    function sequencerMessageCount() external view returns (uint256);

    // ---------- onlySequencerInbox functions ----------

    function enqueueSequencerMessage(
        bytes32 dataHash,
        uint256 afterDelayedMessagesRead,
        uint256 prevMessageCount,
        uint256 newMessageCount
    )
        external
        returns (
            uint256 seqMessageIndex,
            bytes32 beforeAcc,
            bytes32 delayedAcc,
            bytes32 acc
        );

    /**
     * @dev Allows the sequencer inbox to submit a delayed message of the batchPostingReport type
     *      This is done through a separate function entrypoint instead of allowing the sequencer inbox
     *      to call `enqueueDelayedMessage` to avoid the gas overhead of an extra SLOAD in either
     *      every delayed inbox or every sequencer inbox call.
     */
    function submitBatchSpendingReport(address batchPoster, bytes32 dataHash)
        external
        returns (uint256 msgNum);

    // ---------- onlyRollupOrOwner functions ----------

    function setSequencerInbox(address _sequencerInbox) external;

    function setDelayedInbox(address inbox, bool enabled) external;

    function setOutbox(address inbox, bool enabled) external;

    // ---------- initializer ----------

    function initialize(IOwnable rollup_) external;
}


messageNum

InboxMessageDelivered

InboxMessageDeliveredFromOrigin

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.6.9 <0.9.0;

interface IDelayedMessageProvider {
    /// @dev event emitted when a inbox message is added to the Bridge's delayed accumulator
    event InboxMessageDelivered(uint256 indexed messageNum, bytes data);

    /// @dev event emitted when a inbox message is added to the Bridge's delayed accumulator
    /// same as InboxMessageDelivered but the batch data is available in tx.input
    event InboxMessageDeliveredFromOrigin(uint256 indexed messageNum);
}


bridge

dataLength

baseFee

calculateRetryableSubmissionFee

l2CallValue

maxSubmissionCost

excessFeeRefundAddress

callValueRefundAddress

gasLimit

maxFeePerGas

createRetryableTicket

depositEth

_bridge

pause

postUpgradeInit

sendContractTransaction

sendL1FundedContractTransaction

nonce

sendL1FundedUnsignedTransaction

sendL1FundedUnsignedTransactionToFork

messageData

sendL2Message

sendL2MessageFromOrigin

sendUnsignedTransaction

sendUnsignedTransactionToFork

withdrawTo

sendWithdrawEthToFork

unpause

unsafeCreateRetryableTicket

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.6.9 <0.9.0;

import "./IBridge.sol";
import "./IDelayedMessageProvider.sol";
import "./ISequencerInbox.sol";

interface IInbox is IDelayedMessageProvider {
    function bridge() external view returns (IBridge);

    function sequencerInbox() external view returns (ISequencerInbox);

    /**
     * @notice Send a generic L2 message to the chain
     * @dev This method is an optimization to avoid having to emit the entirety of the messageData in a log. Instead validators are expected to be able to parse the data from the transaction's input
     *      This method will be disabled upon L1 fork to prevent replay attacks on L2
     * @param messageData Data of the message being sent
     */
    function sendL2MessageFromOrigin(bytes calldata messageData) external returns (uint256);

    /**
     * @notice Send a generic L2 message to the chain
     * @dev This method can be used to send any type of message that doesn't require L1 validation
     *      This method will be disabled upon L1 fork to prevent replay attacks on L2
     * @param messageData Data of the message being sent
     */
    function sendL2Message(bytes calldata messageData) external returns (uint256);

    function sendL1FundedUnsignedTransaction(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        uint256 nonce,
        address to,
        bytes calldata data
    ) external payable returns (uint256);

    function sendL1FundedContractTransaction(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        address to,
        bytes calldata data
    ) external payable returns (uint256);

    function sendUnsignedTransaction(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        uint256 nonce,
        address to,
        uint256 value,
        bytes calldata data
    ) external returns (uint256);

    function sendContractTransaction(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        address to,
        uint256 value,
        bytes calldata data
    ) external returns (uint256);

    /**
     * @dev This method can only be called upon L1 fork and will not alias the caller
     *      This method will revert if not called from origin
     */
    function sendL1FundedUnsignedTransactionToFork(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        uint256 nonce,
        address to,
        bytes calldata data
    ) external payable returns (uint256);

    /**
     * @dev This method can only be called upon L1 fork and will not alias the caller
     *      This method will revert if not called from origin
     */
    function sendUnsignedTransactionToFork(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        uint256 nonce,
        address to,
        uint256 value,
        bytes calldata data
    ) external returns (uint256);

    /**
     * @notice Send a message to initiate L2 withdrawal
     * @dev This method can only be called upon L1 fork and will not alias the caller
     *      This method will revert if not called from origin
     */
    function sendWithdrawEthToFork(
        uint256 gasLimit,
        uint256 maxFeePerGas,
        uint256 nonce,
        uint256 value,
        address withdrawTo
    ) external returns (uint256);

    /**
     * @notice Get the L1 fee for submitting a retryable
     * @dev This fee can be paid by funds already in the L2 aliased address or by the current message value
     * @dev This formula may change in the future, to future proof your code query this method instead of inlining!!
     * @param dataLength The length of the retryable's calldata, in bytes
     * @param baseFee The block basefee when the retryable is included in the chain, if 0 current block.basefee will be used
     */
    function calculateRetryableSubmissionFee(uint256 dataLength, uint256 baseFee)
        external
        view
        returns (uint256);

    /**
     * @notice Deposit eth from L1 to L2 to address of the sender if sender is an EOA, and to its aliased address if the sender is a contract
     * @dev This does not trigger the fallback function when receiving in the L2 side.
     *      Look into retryable tickets if you are interested in this functionality.
     * @dev This function should not be called inside contract constructors
     */
    function depositEth() external payable returns (uint256);

    /**
     * @notice Put a message in the L2 inbox that can be reexecuted for some fixed amount of time if it reverts
     * @dev all msg.value will deposited to callValueRefundAddress on L2
     * @dev Gas limit and maxFeePerGas should not be set to 1 as that is used to trigger the RetryableData error
     * @param to destination L2 contract address
     * @param l2CallValue call value for retryable L2 message
     * @param maxSubmissionCost Max gas deducted from user's L2 balance to cover base submission fee
     * @param excessFeeRefundAddress gasLimit x maxFeePerGas - execution cost gets credited here on L2 balance
     * @param callValueRefundAddress l2Callvalue gets credited here on L2 if retryable txn times out or gets cancelled
     * @param gasLimit Max gas deducted from user's L2 balance to cover L2 execution. Should not be set to 1 (magic value used to trigger the RetryableData error)
     * @param maxFeePerGas price bid for L2 execution. Should not be set to 1 (magic value used to trigger the RetryableData error)
     * @param data ABI encoded data of L2 message
     * @return unique message number of the retryable transaction
     */
    function createRetryableTicket(
        address to,
        uint256 l2CallValue,
        uint256 maxSubmissionCost,
        address excessFeeRefundAddress,
        address callValueRefundAddress,
        uint256 gasLimit,
        uint256 maxFeePerGas,
        bytes calldata data
    ) external payable returns (uint256);

    /**
     * @notice Put a message in the L2 inbox that can be reexecuted for some fixed amount of time if it reverts
     * @dev Same as createRetryableTicket, but does not guarantee that submission will succeed by requiring the needed funds
     * come from the deposit alone, rather than falling back on the user's L2 balance
     * @dev Advanced usage only (does not rewrite aliases for excessFeeRefundAddress and callValueRefundAddress).
     * createRetryableTicket method is the recommended standard.
     * @dev Gas limit and maxFeePerGas should not be set to 1 as that is used to trigger the RetryableData error
     * @param to destination L2 contract address
     * @param l2CallValue call value for retryable L2 message
     * @param maxSubmissionCost Max gas deducted from user's L2 balance to cover base submission fee
     * @param excessFeeRefundAddress gasLimit x maxFeePerGas - execution cost gets credited here on L2 balance
     * @param callValueRefundAddress l2Callvalue gets credited here on L2 if retryable txn times out or gets cancelled
     * @param gasLimit Max gas deducted from user's L2 balance to cover L2 execution. Should not be set to 1 (magic value used to trigger the RetryableData error)
     * @param maxFeePerGas price bid for L2 execution. Should not be set to 1 (magic value used to trigger the RetryableData error)
     * @param data ABI encoded data of L2 message
     * @return unique message number of the retryable transaction
     */
    function unsafeCreateRetryableTicket(
        address to,
        uint256 l2CallValue,
        uint256 maxSubmissionCost,
        address excessFeeRefundAddress,
        address callValueRefundAddress,
        uint256 gasLimit,
        uint256 maxFeePerGas,
        bytes calldata data
    ) external payable returns (uint256);

    // ---------- onlyRollupOrOwner functions ----------

    /// @notice pauses all inbox functionality
    function pause() external;

    /// @notice unpauses all inbox functionality
    function unpause() external;

    // ---------- initializer ----------

    /**
     * @dev function to be called one time during the inbox upgrade process
     *      this is used to fix the storage slots
     */
    function postUpgradeInit(IBridge _bridge) external;

    function initialize(IBridge _bridge, ISequencerInbox _sequencerInbox) external;
}


owner

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.4.21 <0.9.0;

interface IOwnable {
    function owner() external view returns (address);
}


DATA_AUTHENTICATED_FLAG

HEADER_LENGTH

sequenceNumber

gasRefunder

addSequencerL2Batch

addSequencerL2BatchFromOrigin

batchCount

_totalDelayedMessagesRead

l1BlockAndTime

forceInclusion

ksHash

getKeysetCreationBlock

index

inboxAccs

bridge_

maxTimeVariation_

invalidateKeysetHash

isBatchPoster

isValidKeysetHash

removeDelayAfterFork

addr

isBatchPoster_

setIsBatchPoster

setMaxTimeVariation

keysetBytes

setValidKeyset

totalDelayedMessagesRead

keysetHash

InvalidateKeyset

OwnerFunctionCalled

batchSequenceNumber

SequencerBatchData

afterAcc

timeBounds

dataLocation

SequencerBatchDelivered

SetValidKeyset

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.6.9 <0.9.0;
pragma experimental ABIEncoderV2;

import "../libraries/IGasRefunder.sol";
import "./IDelayedMessageProvider.sol";
import "./IBridge.sol";

interface ISequencerInbox is IDelayedMessageProvider {
    struct MaxTimeVariation {
        uint256 delayBlocks;
        uint256 futureBlocks;
        uint256 delaySeconds;
        uint256 futureSeconds;
    }

    struct TimeBounds {
        uint64 minTimestamp;
        uint64 maxTimestamp;
        uint64 minBlockNumber;
        uint64 maxBlockNumber;
    }

    enum BatchDataLocation {
        TxInput,
        SeparateBatchEvent,
        NoData
    }

    event SequencerBatchDelivered(
        uint256 indexed batchSequenceNumber,
        bytes32 indexed beforeAcc,
        bytes32 indexed afterAcc,
        bytes32 delayedAcc,
        uint256 afterDelayedMessagesRead,
        TimeBounds timeBounds,
        BatchDataLocation dataLocation
    );

    event OwnerFunctionCalled(uint256 indexed id);

    /// @dev a separate event that emits batch data when this isn't easily accessible in the tx.input
    event SequencerBatchData(uint256 indexed batchSequenceNumber, bytes data);

    /// @dev a valid keyset was added
    event SetValidKeyset(bytes32 indexed keysetHash, bytes keysetBytes);

    /// @dev a keyset was invalidated
    event InvalidateKeyset(bytes32 indexed keysetHash);

    function totalDelayedMessagesRead() external view returns (uint256);

    function bridge() external view returns (IBridge);

    /// @dev The size of the batch header
    // solhint-disable-next-line func-name-mixedcase
    function HEADER_LENGTH() external view returns (uint256);

    /// @dev If the first batch data byte after the header has this bit set,
    ///      the sequencer inbox has authenticated the data. Currently not used.
    // solhint-disable-next-line func-name-mixedcase
    function DATA_AUTHENTICATED_FLAG() external view returns (bytes1);

    function rollup() external view returns (IOwnable);

    function isBatchPoster(address) external view returns (bool);

    struct DasKeySetInfo {
        bool isValidKeyset;
        uint64 creationBlock;
    }

    // https://github.com/ethereum/solidity/issues/11826
    // function maxTimeVariation() external view returns (MaxTimeVariation calldata);
    // function dasKeySetInfo(bytes32) external view returns (DasKeySetInfo calldata);

    /// @notice Remove force inclusion delay after a L1 chainId fork
    function removeDelayAfterFork() external;

    /// @notice Force messages from the delayed inbox to be included in the chain
    ///         Callable by any address, but message can only be force-included after maxTimeVariation.delayBlocks and
    ///         maxTimeVariation.delaySeconds has elapsed. As part of normal behaviour the sequencer will include these
    ///         messages so it's only necessary to call this if the sequencer is down, or not including any delayed messages.
    /// @param _totalDelayedMessagesRead The total number of messages to read up to
    /// @param kind The kind of the last message to be included
    /// @param l1BlockAndTime The l1 block and the l1 timestamp of the last message to be included
    /// @param baseFeeL1 The l1 gas price of the last message to be included
    /// @param sender The sender of the last message to be included
    /// @param messageDataHash The messageDataHash of the last message to be included
    function forceInclusion(
        uint256 _totalDelayedMessagesRead,
        uint8 kind,
        uint64[2] calldata l1BlockAndTime,
        uint256 baseFeeL1,
        address sender,
        bytes32 messageDataHash
    ) external;

    function inboxAccs(uint256 index) external view returns (bytes32);

    function batchCount() external view returns (uint256);

    function isValidKeysetHash(bytes32 ksHash) external view returns (bool);

    /// @notice the creation block is intended to still be available after a keyset is deleted
    function getKeysetCreationBlock(bytes32 ksHash) external view returns (uint256);

    // ---------- BatchPoster functions ----------

    function addSequencerL2BatchFromOrigin(
        uint256 sequenceNumber,
        bytes calldata data,
        uint256 afterDelayedMessagesRead,
        IGasRefunder gasRefunder
    ) external;

    function addSequencerL2Batch(
        uint256 sequenceNumber,
        bytes calldata data,
        uint256 afterDelayedMessagesRead,
        IGasRefunder gasRefunder,
        uint256 prevMessageCount,
        uint256 newMessageCount
    ) external;

    // ---------- onlyRollupOrOwner functions ----------

    /**
     * @notice Set max delay for sequencer inbox
     * @param maxTimeVariation_ the maximum time variation parameters
     */
    function setMaxTimeVariation(MaxTimeVariation memory maxTimeVariation_) external;

    /**
     * @notice Updates whether an address is authorized to be a batch poster at the sequencer inbox
     * @param addr the address
     * @param isBatchPoster_ if the specified address should be authorized as a batch poster
     */
    function setIsBatchPoster(address addr, bool isBatchPoster_) external;

    /**
     * @notice Makes Data Availability Service keyset valid
     * @param keysetBytes bytes of the serialized keyset
     */
    function setValidKeyset(bytes calldata keysetBytes) external;

    /**
     * @notice Invalidates a Data Availability Service keyset
     * @param ksHash hash of the keyset
     */
    function invalidateKeysetHash(bytes32 ksHash) external;

    // ---------- initializer ----------

    function initialize(IBridge bridge_, MaxTimeVariation calldata maxTimeVariation_) external;
}


// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

// solhint-disable-next-line compiler-version
pragma solidity >=0.6.9 <0.9.0;

interface IGasRefunder {
    function onGasSpent(
        address payable spender,
        uint256 gasUsed,
        uint256 calldataSize
    ) external returns (bool success);
}

abstract contract GasRefundEnabled {
    /// @dev this refunds the sender for execution costs of the tx
    /// calldata costs are only refunded if `msg.sender == tx.origin` to guarantee the value refunded relates to charging
    /// for the `tx.input`. this avoids a possible attack where you generate large calldata from a contract and get over-refunded
    modifier refundsGas(IGasRefunder gasRefunder) {
        uint256 startGasLeft = gasleft();
        _;
        if (address(gasRefunder) != address(0)) {
            uint256 calldataSize;
            assembly {
                calldataSize := calldatasize()
            }
            uint256 calldataWords = (calldataSize + 31) / 32;
            // account for the CALLDATACOPY cost of the proxy contract, including the memory expansion cost
            startGasLeft += calldataWords * 6 + (calldataWords**2) / 512;
            // if triggered in a contract call, the spender may be overrefunded by appending dummy data to the call
            // so we check if it is a top level call, which would mean the sender paid calldata as part of tx.input
            // solhint-disable-next-line avoid-tx-origin
            if (msg.sender != tx.origin) {
                // We can't be sure if this calldata came from the top level tx,
                // so to be safe we tell the gas refunder there was no calldata.
                calldataSize = 0;
            }
            gasRefunder.onGasSpent(payable(msg.sender), startGasLeft - gasleft(), calldataSize);
        }
    }
}


arbBlockNum

arbBlockHash

arbBlockNumber

arbChainID

arbOSVersion

getStorageGasAvailable

isTopLevelCall

unused

mapL1SenderContractAddressToL2Alias

myCallersAddressWithoutAliasing

sendMerkleTreeState

size

root

partials

destination

sendTxToL1

wasMyCallersAddressAliased

withdrawEth

caller

uniqueId

batchNumber

indexInBatch

ethBlockNum

callvalue

L2ToL1Transaction

hash

position

L2ToL1Tx

reserved

SendMerkleUpdate

// Copyright 2021-2022, Offchain Labs, Inc.
// For license information, see https://github.com/nitro/blob/master/LICENSE
// SPDX-License-Identifier: BUSL-1.1

pragma solidity >=0.4.21 <0.9.0;

/**
 * @title System level functionality
 * @notice For use by contracts to interact with core L2-specific functionality.
 * Precompiled contract that exists in every Arbitrum chain at address(100), 0x0000000000000000000000000000000000000064.
 */
interface ArbSys {
    /**
     * @notice Get Arbitrum block number (distinct from L1 block number; Arbitrum genesis block has block number 0)
     * @return block number as int
     */
    function arbBlockNumber() external view returns (uint256);

    /**
     * @notice Get Arbitrum block hash (reverts unless currentBlockNum-256 <= arbBlockNum < currentBlockNum)
     * @return block hash
     */
    function arbBlockHash(uint256 arbBlockNum) external view returns (bytes32);

    /**
     * @notice Gets the rollup's unique chain identifier
     * @return Chain identifier as int
     */
    function arbChainID() external view returns (uint256);

    /**
     * @notice Get internal version number identifying an ArbOS build
     * @return version number as int
     */
    function arbOSVersion() external view returns (uint256);

    /**
     * @notice Returns 0 since Nitro has no concept of storage gas
     * @return uint 0
     */
    function getStorageGasAvailable() external view returns (uint256);

    /**
     * @notice (deprecated) check if current call is top level (meaning it was triggered by an EoA or a L1 contract)
     * @dev this call has been deprecated and may be removed in a future release
     * @return true if current execution frame is not a call by another L2 contract
     */
    function isTopLevelCall() external view returns (bool);

    /**
     * @notice map L1 sender contract address to its L2 alias
     * @param sender sender address
     * @param unused argument no longer used
     * @return aliased sender address
     */
    function mapL1SenderContractAddressToL2Alias(address sender, address unused)
        external
        pure
        returns (address);

    /**
     * @notice check if the caller (of this caller of this) is an aliased L1 contract address
     * @return true iff the caller's address is an alias for an L1 contract address
     */
    function wasMyCallersAddressAliased() external view returns (bool);

    /**
     * @notice return the address of the caller (of this caller of this), without applying L1 contract address aliasing
     * @return address of the caller's caller, without applying L1 contract address aliasing
     */
    function myCallersAddressWithoutAliasing() external view returns (address);

    /**
     * @notice Send given amount of Eth to dest from sender.
     * This is a convenience function, which is equivalent to calling sendTxToL1 with empty data.
     * @param destination recipient address on L1
     * @return unique identifier for this L2-to-L1 transaction.
     */
    function withdrawEth(address destination) external payable returns (uint256);

    /**
     * @notice Send a transaction to L1
     * @dev it is not possible to execute on the L1 any L2-to-L1 transaction which contains data
     * to a contract address without any code (as enforced by the Bridge contract).
     * @param destination recipient address on L1
     * @param data (optional) calldata for L1 contract call
     * @return a unique identifier for this L2-to-L1 transaction.
     */
    function sendTxToL1(address destination, bytes calldata data)
        external
        payable
        returns (uint256);

    /**
     * @notice Get send Merkle tree state
     * @return size number of sends in the history
     * @return root root hash of the send history
     * @return partials hashes of partial subtrees in the send history tree
     */
    function sendMerkleTreeState()
        external
        view
        returns (
            uint256 size,
            bytes32 root,
            bytes32[] memory partials
        );

    /**
     * @notice creates a send txn from L2 to L1
     * @param position = (level << 192) + leaf = (0 << 192) + leaf = leaf
     */
    event L2ToL1Tx(
        address caller,
        address indexed destination,
        uint256 indexed hash,
        uint256 indexed position,
        uint256 arbBlockNum,
        uint256 ethBlockNum,
        uint256 timestamp,
        uint256 callvalue,
        bytes data
    );

    /// @dev DEPRECATED in favour of the new L2ToL1Tx event above after the nitro upgrade
    event L2ToL1Transaction(
        address caller,
        address indexed destination,
        uint256 indexed uniqueId,
        uint256 indexed batchNumber,
        uint256 indexInBatch,
        uint256 arbBlockNum,
        uint256 ethBlockNum,
        uint256 timestamp,
        uint256 callvalue,
        bytes data
    );

    /**
     * @notice logs a merkle branch for proof synthesis
     * @param reserved an index meant only to align the 4th index with L2ToL1Transaction's 4th event
     * @param hash the merkle hash
     * @param position = (level << 192) + leaf
     */
    event SendMerkleUpdate(
        uint256 indexed reserved,
        bytes32 indexed hash,
        uint256 indexed position
    );
}


System level functionality

_inbox

_l2Target

createL2Message

handleMessageFromL2

l2Target

numberFromL2

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

import {L2Contract} from "./L2Contract.sol";
import {IInbox} from "@arbitrum/nitro-contracts/src/bridge/IInbox.sol";

/// @title L1Contract
/// @notice An example L1 contract that interacts with an L2 contract (sends & receives messages)
/// @author saucepoint
contract L1Contract {
    // A number set by an L2-to-L1 message
    uint256 public numberFromL2;

    // Address of the L2 contract
    address public immutable l2Target;

    // Arbitrum Inbox (message handler)
    IInbox public inbox;

    constructor(address _inbox, address _l2Target) {
        inbox = IInbox(_inbox);
        l2Target = _l2Target;
    }

    /// @notice Sends a message to the L2 contract (set a uint256)
    /// @param number The number to set on the L2 contract state
    function createL2Message(uint256 number) external payable {
        bytes memory data = abi.encodeWithSelector(L2Contract.handleMessageFromL1.selector, number);

        // In production, these values should be set by the caller
        // It's the gas that is paid for L2 txn execution
        uint256 maxSubmissionCost = 0.1 ether;
        uint256 maxGas = 1_000_000;
        uint256 gasPriceBid = 10 gwei;

        // Send the message to the L2 contract
        // (~10 min delay, but is executed immediately in tests)
        inbox.createRetryableTicket{value: msg.value}(
            l2Target, 0, maxSubmissionCost, msg.sender, msg.sender, maxGas, gasPriceBid, data
        );
    }

    /// @notice Handles a message originating from L2
    /// @param number The number to set on the L1 contract state, provided by a message from L2
    function handleMessageFromL2(uint256 number) external {
        // Do something with the number
        numberFromL2 = number;
    }
}


L1Contract

L2Contract is an example Layer 2 (L2) contract on Arbitrum that interacts with a Layer 1 (L1) contract. It can send messages to the L1 contract to set a uint256 value and handle incoming messages from the L1 contract to update its own state. The contract includes functions to set the L1 contract address, send messages to L1, and handle messages from L1, updating a stored number accordingly.