VIAMintBurnTokenCardano

A cross-chain ERC20 token for routes that include Cardano. It burns on the source chain and mints on the destination, like VIAMintBurnTokenMinimal. The difference is the message format. This contract packs every message in VILR, the format that VIA's Cardano clients read and write.

Use when your token lives on Cardano and on one or more EVM chains. Deploy this contract on every EVM chain in the route. VIAMintBurnTokenMinimal encodes its message with abi.encode, and a Cardano client cannot decode that format.

The contract also sends to and receives from other EVM chains, because both sides pack and read the same layout. Transfers between two EVM chains go direct. They do not pass through Cardano.

For the full source code, see Contract Source. For the Cardano side of the route, see Burn & Mint Client.

Inherits: ERC20, ERC20Burnable, Ownable, ViaIntegrationV1

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Constructor

constructor(
    string memory name,
    string memory symbol,
    uint256 initialSupply,
    bytes32 cardanoToken
)

Parameter	Type	Description
name	string	Token name (e.g., "My Token")
symbol	string	Token symbol (e.g., "MTK")
initialSupply	uint256	Supply in whole tokens — multiplied by 10 ** decimals()
cardanoToken	bytes32	Cross-chain identity of the token on Cardano: keccak256(policyId ++ assetName). See Token Identity.

The contract stores cardanoToken as an immutable value. You cannot change it after deployment. The constructor reverts with InvalidMessage if the value is zero.

The total supply across all chains is the sum of the initial supplies. If the full supply mints on Cardano at init, pass 0 for initialSupply.

Deployer becomes both the ERC20 owner and the ViaIntegrationV1 projectOwner.

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Functions

decimals

function decimals() public pure override returns (uint8);

Returns 6. Amounts cross chains as raw integers, with no scaling. The value must equal the decimals of the token on Cardano. If your Cardano token uses another value, change this function before you deploy.

mint

function mint(address to, uint256 amount) external onlyOwner;

Mint tokens to any address. Restricted to owner. No burn on another chain matches these tokens, so they raise the total supply across chains.

bridge

function bridge(
    bytes32 tokenRecipient,
    uint64 destChainId,
    uint256 amount,
    string calldata text
) external payable returns (uint256 txId);

Burn tokens from msg.sender on this chain and send a VILR message to mint on the destination.

Parameter	Type	Description
tokenRecipient	bytes32	Recipient on the destination chain. The format depends on the destination. See Recipient Format.
destChainId	uint64	Destination chain ID. For Cardano, use the VIA chain ID: 2273265 for Mainnet, 2273266 for Preprod.
amount	uint256	Amount to transfer, in base units
text	string	Not used. The VILR payload has no text field.

Include msg.value if the gateway requires fees. Returns a txId for tracking.

messageProcess

function messageProcess(
    uint256 txId, uint64 sourceChainId, bytes32 sender, bytes32 recipient,
    bytes memory onChainData, bytes memory offChainData, uint256 gasRefundAmount
) internal override;

Called automatically by the gateway. Reads amount and destination_recipient from the VILR payload in onChainData, converts the recipient to an address, and mints to it. It does not read the other payload fields.

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Recipient Format

tokenRecipient is always 32 bytes. What goes in it depends on the destination chain.

Destination	Format
EVM chain	The address, left-padded with zeros. Use _addressToBytes32().
Cardano	A 4-byte tag, then the 28-byte credential hash. Tag 0x00000001 is a payment key hash. Tag 0x00000002 is a script hash.

A Cardano recipient with a payment key looks like this:

0x00000001 ++ <28-byte payment key hash>

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Endpoints

Set one endpoint for each chain in the route, in both directions.

• On this contract: call setMessageEndpoints(). For Cardano, the endpoint is the policy ID of your Cardano client, left-padded with zeros to 32 bytes. For another EVM chain, the endpoint is the address of this contract on that chain, left-padded the same way.
• On Cardano: add this contract to the route list of your client. The source_chain is the EVM chain ID. The sender is this contract's address, left-padded with zeros to 32 bytes.

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Message Encoding

// bridge() packs 204 bytes:
abi.encodePacked(
    bytes4(0x56494c52),  // magic "VILR"
    uint32(1),           // version
    amount,              // uint256
    CARDANO_TOKEN,       // source_token
    uint32(0),           // source depositor prefix (reserved)
    bytes28(0),          // source depositor (not set)
    CARDANO_TOKEN,       // destination_token
    tokenRecipient,      // destination_recipient
    uint256(0),          // max_fee
    uint32(0)            // hook_data length
)

// messageProcess() reads:
// amount          at byte offset 8
// tokenRecipient  at byte offset 136

The contract always sends a max_fee of zero and no hook data. With no hook data, the Cardano output that pays the recipient carries no datum. For the full layout, see The chain_data Format (VILR).

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Errors

Error	When
ZeroAmount	bridge() called with amount == 0
InvalidMessage	Decoded amount < 1 or recipient is zero address. Also thrown by the constructor when cardanoToken is zero.

Burns are irreversible. If delivery fails on the destination, tokens are already burned on the source. On an EVM destination, recovery requires the owner to manually mint() replacements. The Cardano client has no owner mint.