Inbox

The Inbox is a contract deployed on L1 that handles message passing from L1 to L2.

Links: Interface, Implementation.

sendL2Message()

Sends a message from L1 to L2.

send_l1_to_l2_message

/**
 * @notice Inserts a new message into the Inbox
 * @dev Emits `MessageSent` with data for easy access by the sequencer
 * @param _recipient - The recipient of the message
 * @param _content - The content of the message (application specific)
 * @param _secretHash - The secret hash of the message (make it possible to hide when a specific message is consumed
 * on L2)
 * @return The key of the message in the set and its leaf index in the tree
 */
function sendL2Message(DataStructures.L2Actor memory _recipient, bytes32 _content, bytes32 _secretHash)
  external
  returns (bytes32, uint256);

^{_{Source code: l1-contracts/src/core/interfaces/messagebridge/IInbox.sol#L35-L48}}

Name	Type	Description
Recipient	L2Actor	The recipient of the message. The recipient's version MUST match the inbox version and the actor must be an Aztec contract that is attached to the contract making this call. If the recipient is not attached to the caller, the message cannot be consumed by it.
Content	field (~254 bits)	The content of the message. This is the data that will be passed to the recipient. The content is limited to a single field for rollup purposes. If the content is small enough it can be passed directly, otherwise it should be hashed and the hash passed along (you can use our Hash utilities with sha256ToField functions).
Secret Hash	field (~254 bits)	A hash of a secret used when consuming the message on L2. Keep this preimage secret to make the consumption private. To consume the message the caller must know the pre-image (the value that was hashed). Use computeSecretHash to compute it from a secret.
ReturnValue	(bytes32, uint256)	The message hash (used as an identifier) and the leaf index in the tree.

Edge cases

• Will revert with Inbox__ActorTooLarge(bytes32 actor) if the recipient actor is larger than the field size (~254 bits).
• Will revert with Inbox__VersionMismatch(uint256 expected, uint256 actual) if the recipient version doesn't match the inbox version.
• Will revert with Inbox__ContentTooLarge(bytes32 content) if the content is larger than the field size (~254 bits).
• Will revert with Inbox__SecretHashTooLarge(bytes32 secretHash) if the secret hash is larger than the field size (~254 bits).
• Will revert with Inbox__Ignition() during the ignition phase (when the rollup's mana target is 0).

View functions

These functions allow you to query the current state of the Inbox.

Function	Returns	Description
getRoot(uint256)	bytes32	Returns the root of a message tree for a given checkpoint number.
getState()	InboxState	Returns the current inbox state (rolling hash, total messages inserted, in-progress checkpoint).
getTotalMessagesInserted()	uint64	Returns the total number of messages inserted into the inbox.
getInProgress()	uint64	Returns the checkpoint number currently being filled.
getFeeAssetPortal()	address	Returns the address of the Fee Juice portal.

Internal functions

note

The following functions are only callable by the Rollup contract and are documented here for completeness.

consume()

Consumes a message tree for a given checkpoint number.

consume

/**
 * @notice Consumes the current tree, and starts a new one if needed
 * @dev Only callable by the rollup contract
 * @dev In the first iteration we return empty tree root because first checkpoint's messages tree is always
 * empty because there has to be a 1 checkpoint lag to prevent sequencer DOS attacks
 *
 * @param _toConsume - The checkpoint number to consume
 *
 * @return The root of the consumed tree
 */
function consume(uint256 _toConsume) external returns (bytes32);

^{_{Source code: l1-contracts/src/core/interfaces/messagebridge/IInbox.sol#L50-L62}}

Name	Type	Description
_toConsume	uint256	The checkpoint number to consume.
ReturnValue	bytes32	The root of the consumed message tree.

Edge cases

• Will revert with Inbox__Unauthorized() if msg.sender != ROLLUP.
• Will revert with Inbox__MustBuildBeforeConsume() if trying to consume a checkpoint that hasn't been built yet.

Related pages

• Outbox - L2 to L1 message passing
• Data Structures - Message and actor type definitions