VIALockerRelease

A cross-chain bridge that locks tokens on the source chain and releases from a pre-funded pool on the destination. Users receive the original token on both sides — no synthetics or wrapped versions.

Use when you don't control the token (USDC, WETH, etc.) and can manage liquidity on each destination chain.

For the full source code, see Contract Source. For the deployment walkthrough, see Lock & Release Token.

Inherits: Ownable, ViaIntegrationV1

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Constructor

constructor(address _token)

Parameter	Type	Description
_token	address	The ERC20 token this bridge handles. Immutable after deployment.

The token address can differ per chain (e.g., USDC has different addresses on Ethereum vs Polygon). Deployer becomes both owner and projectOwner.

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Functions

bridge

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

Lock tokens from msg.sender and send a release message to the destination. Caller must have approved this contract first.

Parameter	Type	Description
tokenRecipient	bytes32	Recipient on destination chain (left-padded). Use _addressToBytes32().
destChainId	uint64	Destination chain ID
amount	uint256	Amount to bridge (in wei)

Include msg.value for destination gas.

deposit

function deposit(uint256 amount) external;

Fund the liquidity pool on this chain. Anyone can call — not restricted to owner. Caller must have approved this contract. Destination chains must be funded before users can bridge to them.

withdraw

function withdraw(IERC20 tokenAddress, uint256 amount) external onlyOwner;

Withdraw tokens from the contract. Accepts any ERC20 address (not just the configured token), so it can recover accidentally-sent tokens too.

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. Decodes (bytes32 tokenRecipient, uint256 amount) from onChainData and releases tokens from the pool.

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Message Encoding

// bridge() encodes:
abi.encode(bytes32 tokenRecipient, uint256 amount)

// messageProcess() decodes:
(bytes32 tokenRecipient, uint256 amount) = abi.decode(onChainData, (bytes32, uint256));

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Errors

Error	When
ZeroAmount	bridge() or deposit() called with amount == 0
InvalidMessage	Decoded amount < 1 or recipient is zero address
InsufficientLiquidity	Pool doesn't have enough tokens to release
InsufficientBalance	withdraw() amount exceeds contract balance

What happens when liquidity runs out

If messageProcess() reverts with InsufficientLiquidity:

1. The gateway emits an Error event
2. The message is marked as processed (cannot be replayed)
3. Tokens remain locked on the source chain
4. Recovery requires manual intervention — fund the pool and coordinate with VIA Labs, or the owner releases source tokens directly

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Liquidity

• Monitor token.balanceOf(bridgeAddress) on every destination chain
• Watch the gateway Error event — fires when a release fails
• Use a multisig as the owner in production — the owner can withdraw all liquidity
• deposit() is permissionless — no per-depositor accounting. Deposits are effectively donations to the pool.