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Overview

The GnosisBridgeFacet enables bridging of ETH and ERC20 tokens from Ethereum mainnet to Gnosis Chain (formerly xDai Chain) using the official Gnosis bridge infrastructure.

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Contract Interface

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Functions

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startBridgeTokensViaGnosisBridge

Bridges tokens from Ethereum to Gnosis Chain. 
function startBridgeTokensViaGnosisBridge(
  BridgeData _bridgeData
) external
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_bridgeData
BridgeData
Standard bridge data containing transaction details

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swapAndStartBridgeTokensViaGnosisBridge

Performs a token swap on Ethereum before bridging to Gnosis Chain. 
function swapAndStartBridgeTokensViaGnosisBridge(
  BridgeData _bridgeData,
  SwapData[] _swapData
) external payable
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_bridgeData
BridgeData
Standard bridge data
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_swapData
SwapData[]
Array of swap operations to execute before bridging

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Usage Example

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Bridging DAI to Gnosis (becomes xDai)

import { GnosisBridgeFacet } from '@lifi/contract-types';

const gnosisFacet = GnosisBridgeFacet__factory.connect(facetAddress, signer);

const bridgeData = {
  transactionId: ethers.utils.randomBytes(32),
  bridge: 'gnosis',
  integrator: 'my-dapp',
  referrer: '0x0000000000000000000000000000000000000000',
  sendingAssetId: '0x6B175474E89094C44Da98b954EedeAC495271d0F', // DAI on Ethereum
  receiver: await signer.getAddress(),
  minAmount: ethers.utils.parseUnits('100', 18),
  destinationChainId: 100, // Gnosis Chain
  hasSourceSwaps: false,
  hasDestinationCall: false
};

// Approve DAI first
const dai = new ethers.Contract(
  bridgeData.sendingAssetId,
  ['function approve(address spender, uint256 amount) returns (bool)'],
  signer
);

await dai.approve(gnosisFacet.address, bridgeData.minAmount);

// Bridge DAI to xDai
const tx = await gnosisFacet.startBridgeTokensViaGnosisBridge(bridgeData);

await tx.wait();

console.log('DAI bridged. Will arrive as xDai on Gnosis Chain.');

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Bridging ERC20 Tokens

const bridgeData = {
  transactionId: ethers.utils.randomBytes(32),
  bridge: 'gnosis',
  integrator: 'my-dapp',
  referrer: '0x0000000000000000000000000000000000000000',
  sendingAssetId: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48', // USDC on Ethereum
  receiver: await signer.getAddress(),
  minAmount: ethers.utils.parseUnits('1000', 6),
  destinationChainId: 100,
  hasSourceSwaps: false,
  hasDestinationCall: false
};

// Approve USDC
const usdc = new ethers.Contract(
  bridgeData.sendingAssetId,
  ['function approve(address spender, uint256 amount) returns (bool)'],
  signer
);

await usdc.approve(gnosisFacet.address, bridgeData.minAmount);

// Bridge tokens
const tx = await gnosisFacet.startBridgeTokensViaGnosisBridge(bridgeData);

await tx.wait();

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Swap and Bridge

const swapData = [{
  callTo: uniswapRouter,
  approveTo: uniswapRouter,
  sendingAssetId: wethAddress,
  receivingAssetId: daiAddress,
  fromAmount: ethers.utils.parseEther('1'),
  callData: swapCalldata,
  requiresDeposit: true
}];

const bridgeData = {
  transactionId: ethers.utils.randomBytes(32),
  bridge: 'gnosis',
  integrator: 'my-dapp',
  referrer: '0x0000000000000000000000000000000000000000',
  sendingAssetId: daiAddress,
  receiver: await signer.getAddress(),
  minAmount: ethers.utils.parseUnits('1800', 18), // Min DAI expected
  destinationChainId: 100,
  hasSourceSwaps: true,
  hasDestinationCall: false
};

const tx = await gnosisFacet.swapAndStartBridgeTokensViaGnosisBridge(
  bridgeData,
  swapData
);

await tx.wait();

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Events

  • LiFiTransferStarted(BridgeData bridgeData) - Emitted when bridge transfer is initiated
  • LiFiTransferCompleted - Emitted when transfer completes
  • AssetSwapped - Emitted when using swapAndStart variant

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Notes

  • This facet only supports bridging FROM Ethereum mainnet TO Gnosis Chain
  • DAI bridged to Gnosis becomes xDai (the native gas token)
  • Other ERC20 tokens are bridged to their wrapped/mapped versions on Gnosis
  • Bridging typically takes a few minutes for finality
  • The bridge uses the Arbitrary Message Bridge (AMB) for ERC20 tokens
  • Tokens must be approved before bridging

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Token Bridging

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DAI → xDai

DAI from Ethereum becomes xDai (native token) on Gnosis Chain with 1:1 ratio.

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Other ERC20 Tokens

ERC20 tokens are bridged using the OmniBridge, creating wrapped versions on Gnosis Chain.

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Bridge Times

  • Ethereum → Gnosis: ~5 minutes
  • Gnosis → Ethereum: ~5 minutes + challenge period

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See Also

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