MulticallLibraryV2

The MulticallLibraryV2 provides efficient batch execution of multiple function calls in a single transaction, optimized for gas efficiency and error handling.

Overview

MulticallLibraryV2 enables developers to execute multiple contract calls atomically, reducing gas costs and improving user experience by bundling operations together.

Library Interface

library MulticallLibraryV2 {
    struct Call {
        address target;
        bytes callData;
        uint256 gasLimit;
    }
    
    struct CallWithValue {
        address target;
        bytes callData;
        uint256 value;
        uint256 gasLimit;
    }
    
    struct Result {
        bool success;
        bytes returnData;
        uint256 gasUsed;
    }
    
    function multicall(Call[] memory calls) external returns (Result[] memory results);
    function multicallWithValue(CallWithValue[] memory calls) external payable returns (Result[] memory results);
    function tryMulticall(Call[] memory calls) external returns (Result[] memory results);
    function aggregate(Call[] memory calls) external returns (uint256 blockNumber, bytes[] memory returnData);
}

Core Functions

multicall

Executes multiple calls and reverts if any call fails.

function multicall(Call[] memory calls) external returns (Result[] memory results)

Parameters:

• calls: Array of Call structs containing target addresses and call data

Returns:

• results: Array of Result structs with success status, return data, and gas used

Example:

MulticallLibraryV2.Call[] memory calls = new MulticallLibraryV2.Call[](2);

calls[0] = MulticallLibraryV2.Call({
    target: tokenAddress,
    callData: abi.encodeWithSignature("transfer(address,uint256)", recipient, amount),
    gasLimit: 100000
});

calls[1] = MulticallLibraryV2.Call({
    target: stakingAddress,
    callData: abi.encodeWithSignature("stake(uint256)", amount),
    gasLimit: 150000
});

MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.multicall(calls);

multicallWithValue

Executes multiple calls with ETH value, reverting if any call fails.

function multicallWithValue(CallWithValue[] memory calls) external payable returns (Result[] memory results)

Parameters:

• calls: Array of CallWithValue structs including ETH value for each call

Returns:

• results: Array of Result structs with execution details

Example:

MulticallLibraryV2.CallWithValue[] memory calls = new MulticallLibraryV2.CallWithValue[](2);

calls[0] = MulticallLibraryV2.CallWithValue({
    target: wethAddress,
    callData: abi.encodeWithSignature("deposit()"),
    value: 1 ether,
    gasLimit: 50000
});

calls[1] = MulticallLibraryV2.CallWithValue({
    target: dexAddress,
    callData: abi.encodeWithSignature("swap(address,address,uint256)", tokenA, tokenB, amount),
    value: 0,
    gasLimit: 200000
});

MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.multicallWithValue{value: 1 ether}(calls);

tryMulticall

Executes multiple calls without reverting on individual call failures.

function tryMulticall(Call[] memory calls) external returns (Result[] memory results)

Parameters:

• calls: Array of Call structs to execute

Returns:

• results: Array of Result structs, including failed calls

Example:

MulticallLibraryV2.Call[] memory calls = new MulticallLibraryV2.Call[](3);

// Some calls might fail, but execution continues
calls[0] = MulticallLibraryV2.Call({
    target: tokenA,
    callData: abi.encodeWithSignature("transfer(address,uint256)", recipient, amount1),
    gasLimit: 100000
});

calls[1] = MulticallLibraryV2.Call({
    target: tokenB,
    callData: abi.encodeWithSignature("transfer(address,uint256)", recipient, amount2),
    gasLimit: 100000
});

calls[2] = MulticallLibraryV2.Call({
    target: invalidAddress, // This might fail
    callData: abi.encodeWithSignature("someFunction()"),
    gasLimit: 50000
});

MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.tryMulticall(calls);

// Check individual results
for (uint i = 0; i < results.length; i++) {
    if (results[i].success) {
        // Handle successful call
    } else {
        // Handle failed call
        string memory error = abi.decode(results[i].returnData, (string));
    }
}

aggregate

Legacy function for basic multicall aggregation.

function aggregate(Call[] memory calls) external returns (uint256 blockNumber, bytes[] memory returnData)

Parameters:

• calls: Array of Call structs to execute

Returns:

• blockNumber: Current block number

• returnData: Array of return data from each call

Advanced Usage Patterns

1. DeFi Batch Operations

contract DeFiBatchOperations {
    using MulticallLibraryV2 for MulticallLibraryV2.Call[];
    
    function swapAndStake(
        address tokenIn,
        address tokenOut,
        uint256 amountIn,
        address dexRouter,
        address stakingContract
    ) external {
        MulticallLibraryV2.Call[] memory calls = new MulticallLibraryV2.Call[](3);
        
        // 1. Approve token for DEX
        calls[0] = MulticallLibraryV2.Call({
            target: tokenIn,
            callData: abi.encodeWithSignature("approve(address,uint256)", dexRouter, amountIn),
            gasLimit: 50000
        });
        
        // 2. Swap tokens
        calls[1] = MulticallLibraryV2.Call({
            target: dexRouter,
            callData: abi.encodeWithSignature(
                "swapExactTokensForTokens(uint256,uint256,address[],address,uint256)",
                amountIn,
                0, // Accept any amount of tokens out
                getPath(tokenIn, tokenOut),
                address(this),
                block.timestamp + 300
            ),
            gasLimit: 200000
        });
        
        // 3. Stake received tokens
        calls[2] = MulticallLibraryV2.Call({
            target: stakingContract,
            callData: abi.encodeWithSignature("stakeAll()"),
            gasLimit: 150000
        });
        
        MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.multicall(calls);
        
        // Verify all operations succeeded
        for (uint i = 0; i < results.length; i++) {
            require(results[i].success, "Batch operation failed");
        }
    }
}

2. NFT Batch Minting

contract NFTBatchMinter {
    function batchMint(
        address nftContract,
        address[] memory recipients,
        uint256[] memory tokenIds
    ) external {
        require(recipients.length == tokenIds.length, "Array length mismatch");
        
        MulticallLibraryV2.Call[] memory calls = new MulticallLibraryV2.Call[](recipients.length);
        
        for (uint i = 0; i < recipients.length; i++) {
            calls[i] = MulticallLibraryV2.Call({
                target: nftContract,
                callData: abi.encodeWithSignature(
                    "mint(address,uint256)",
                    recipients[i],
                    tokenIds[i]
                ),
                gasLimit: 100000
            });
        }
        
        MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.multicall(calls);
        
        uint256 successCount = 0;
        for (uint i = 0; i < results.length; i++) {
            if (results[i].success) {
                successCount++;
            }
        }
        
        emit BatchMintCompleted(successCount, recipients.length);
    }
}

3. Cross-Chain Batch Operations

contract CrossChainBatchOps {
    IIU2UGateway public gateway;
    
    function batchCrossChainCalls(
        string[] memory destinationChains,
        address[] memory targetContracts,
        bytes[] memory payloads
    ) external {
        require(
            destinationChains.length == targetContracts.length &&
            targetContracts.length == payloads.length,
            "Array length mismatch"
        );
        
        MulticallLibraryV2.Call[] memory calls = new MulticallLibraryV2.Call[](destinationChains.length);
        
        for (uint i = 0; i < destinationChains.length; i++) {
            calls[i] = MulticallLibraryV2.Call({
                target: address(gateway),
                callData: abi.encodeWithSignature(
                    "callContract(string,string,bytes)",
                    destinationChains[i],
                    Strings.toHexString(uint160(targetContracts[i]), 20),
                    payloads[i]
                ),
                gasLimit: 200000
            });
        }
        
        MulticallLibraryV2.Result[] memory results = MulticallLibraryV2.tryMulticall(calls);
        
        emit BatchCrossChainCompleted(results);
    }
}

Gas Optimization Features

Dynamic Gas Limit Adjustment

library GasOptimizedMulticall {
    function optimizedMulticall(
        MulticallLibraryV2.Call[] memory calls,
        uint256 baseGasPerCall
    ) external returns (MulticallLibraryV2.Result[] memory results) {
        results = new MulticallLibraryV2.Result[](calls.length);
        
        for (uint256 i = 0; i < calls.length; i++) {
            uint256 gasStart = gasleft();
            
            // Adjust gas limit based on remaining gas
            uint256 adjustedGasLimit = calls[i].gasLimit;
            if (gasStart < calls[i].gasLimit + baseGasPerCall) {
                adjustedGasLimit = gasStart - baseGasPerCall;
            }
            
            (bool success, bytes memory returnData) = calls[i].target.call{
                gas: adjustedGasLimit
            }(calls[i].callData);
            
            uint256 gasUsed = gasStart - gasleft();
            
            results[i] = MulticallLibraryV2.Result({
                success: success,
                returnData: returnData,
                gasUsed: gasUsed
            });
            
            if (!success && calls[i].gasLimit == adjustedGasLimit) {
                // If call failed and we used full gas limit, revert
                revert("Multicall failed");
            }
        }
        
        return results;
    }
}

Gas Estimation

contract MulticallGasEstimator {
    function estimateMulticallGas(
        MulticallLibraryV2.Call[] memory calls
    ) external returns (uint256[] memory gasEstimates) {
        gasEstimates = new uint256[](calls.length);
        
        for (uint256 i = 0; i < calls.length; i++) {
            try this.estimateSingleCall(calls[i]) returns (uint256 estimate) {
                gasEstimates[i] = estimate;
            } catch {
                gasEstimates[i] = calls[i].gasLimit; // Fallback to provided limit
            }
        }
        
        return gasEstimates;
    }
    
    function estimateSingleCall(
        MulticallLibraryV2.Call memory call
    ) external returns (uint256) {
        return ITargetContract(call.target).estimateGas(call.callData);
    }
}

Error Handling

Custom Error Types

library MulticallErrors {
    error CallFailed(uint256 callIndex, address target, bytes callData, bytes reason);
    error InsufficientGas(uint256 callIndex, uint256 required, uint256 available);
    error InvalidCallData(uint256 callIndex, bytes callData);
    error TargetNotContract(uint256 callIndex, address target);
}

Enhanced Error Reporting

contract EnhancedMulticall {
    using MulticallLibraryV2 for MulticallLibraryV2.Call[];
    
    function safeMulticall(
        MulticallLibraryV2.Call[] memory calls
    ) external returns (MulticallLibraryV2.Result[] memory results) {
        results = new MulticallLibraryV2.Result[](calls.length);
        
        for (uint256 i = 0; i < calls.length; i++) {
            // Validate target is a contract
            if (calls[i].target.code.length == 0) {
                revert MulticallErrors.TargetNotContract(i, calls[i].target);
            }
            
            // Check gas availability
            if (gasleft() < calls[i].gasLimit + 5000) {
                revert MulticallErrors.InsufficientGas(i, calls[i].gasLimit, gasleft());
            }
            
            uint256 gasStart = gasleft();
            
            (bool success, bytes memory returnData) = calls[i].target.call{
                gas: calls[i].gasLimit
            }(calls[i].callData);
            
            uint256 gasUsed = gasStart - gasleft();
            
            results[i] = MulticallLibraryV2.Result({
                success: success,
                returnData: returnData,
                gasUsed: gasUsed
            });
            
            if (!success) {
                revert MulticallErrors.CallFailed(i, calls[i].target, calls[i].callData, returnData);
            }
        }
        
        return results;
    }
}

Security Considerations

Reentrancy Protection

contract ReentrancyProtectedMulticall {
    bool private locked;
    
    modifier nonReentrant() {
        require(!locked, "Reentrant call");
        locked = true;
        _;
        locked = false;
    }
    
    function secureMulticall(
        MulticallLibraryV2.Call[] memory calls
    ) external nonReentrant returns (MulticallLibraryV2.Result[] memory) {
        return MulticallLibraryV2.multicall(calls);
    }
}

Access Control

contract AccessControlledMulticall {
    mapping(address => bool) public authorized;
    mapping(address => bool) public allowedTargets;
    
    modifier onlyAuthorized() {
        require(authorized[msg.sender], "Not authorized");
        _;
    }
    
    function authorizedMulticall(
        MulticallLibraryV2.Call[] memory calls
    ) external onlyAuthorized returns (MulticallLibraryV2.Result[] memory) {
        // Validate all targets are allowed
        for (uint256 i = 0; i < calls.length; i++) {
            require(allowedTargets[calls[i].target], "Target not allowed");
        }
        
        return MulticallLibraryV2.multicall(calls);
    }
}

Integration Examples

Frontend JavaScript

class MulticallManager {
    constructor(contractAddress, provider) {
        this.contract = new ethers.Contract(contractAddress, multicallABI, provider);
    }

    async prepareCalls(operations) {
        const calls = [];
        
        for (const op of operations) {
            const target = op.contract.address || op.contract.target;
            const callData = op.contract.interface.encodeFunctionData(op.method, op.args);
            
            calls.push({
                target: target,
                callData: callData,
                gasLimit: op.gasLimit || 200000
            });
        }
        
        return calls;
    }

    async executeMulticall(calls, options = {}) {
        try {
            const tx = await this.contract.multicall(calls, {
                gasLimit: options.gasLimit || 1000000,
                gasPrice: options.gasPrice
            });
            
            const receipt = await tx.wait();
            return this.parseResults(receipt);
        } catch (error) {
            console.error('Multicall failed:', error);
            throw error;
        }
    }

    async estimateGas(calls) {
        try {
            return await this.contract.estimateGas.multicall(calls);
        } catch (error) {
            console.error('Gas estimation failed:', error);
            return BigInt(1000000); // Fallback
        }
    }

    parseResults(receipt) {
        const results = [];
        
        // Parse MulticallExecuted events
        const events = receipt.logs.filter(log => 
            log.topics[0] === ethers.id("MulticallExecuted(uint256,bool,bytes)")
        );
        
        for (const event of events) {
            const decoded = ethers.AbiCoder.defaultAbiCoder().decode(
                ['uint256', 'bool', 'bytes'],
                event.data
            );
            
            results.push({
                callIndex: decoded[0],
                success: decoded[1],
                returnData: decoded[2]
            });
        }
        
        return results;
    }
}

React Hook

import { useState, useCallback } from 'react';
import { useContract, useSigner } from 'wagmi';

export function useMulticall(contractAddress) {
    const { data: signer } = useSigner();
    const [isLoading, setIsLoading] = useState(false);
    const [error, setError] = useState(null);

    const multicallContract = useContract({
        address: contractAddress,
        abi: multicallABI,
        signerOrProvider: signer
    });

    const executeBatch = useCallback(async (operations) => {
        if (!multicallContract) return;

        setIsLoading(true);
        setError(null);

        try {
            const manager = new MulticallManager(contractAddress, signer.provider);
            const calls = await manager.prepareCalls(operations);
            
            const gasEstimate = await manager.estimateGas(calls);
            const results = await manager.executeMulticall(calls, {
                gasLimit: gasEstimate * 110n / 100n // 10% buffer
            });

            return results;
        } catch (err) {
            setError(err.message);
            throw err;
        } finally {
            setIsLoading(false);
        }
    }, [multicallContract, contractAddress, signer]);

    return {
        executeBatch,
        isLoading,
        error
    };
}

Performance Metrics

Operation Type	Gas Savings	Execution Time	Max Batch Size
Token Transfers	60-80%	40-60% faster	50-100 calls
NFT Operations	50-70%	30-50% faster	20-50 calls
DeFi Interactions	40-60%	50-70% faster	10-30 calls
Cross-Chain Calls	30-50%	60-80% faster	5-20 calls

Best Practices

1. Gas Optimization

• Set appropriate gas limits for each call

• Use tryMulticall for non-critical operations

• Batch similar operations together

• Monitor gas usage patterns

2. Error Handling

• Always check individual call results

• Implement proper fallback mechanisms

• Use descriptive error messages

• Log failed operations for debugging

3. Security

• Validate all target addresses

• Implement access controls where needed

• Use reentrancy protection

• Audit multicall implementations

4. User Experience

• Provide clear transaction previews

• Show individual operation status

• Implement retry mechanisms

• Optimize for mobile gas limits

Resources

• Cross-Chain Architecture

• Gas Management

• Integration Examples

• Security Best Practices