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Ethereum Methods

Specialized Keccak256 methods for Ethereum protocol operations: function selectors, event topics, and contract address derivation (CREATE/CREATE2).

View executable examples: function-selector.ts | event-topic.ts | contract-address-create.ts | contract-address-create2.ts

selector(signature)

Compute function selector (first 4 bytes of Keccak256 hash). Signature:

function selector(signature: string): Uint8Array

Parameters:

signature (string) - Function signature (e.g., "transfer(address,uint256)")

Returns: Uint8Array (4 bytes) - Function selector Throws: Never throws for valid signature string

Basic Usage
Building Calldata
Common Selectors
Selector Lookup

import { Keccak256 } from '@tevm/voltaire/Keccak256';

const selector = Keccak256.selector('transfer(address,uint256)');
// Uint8Array(4) [0xa9, 0x05, 0x9c, 0xbb]

console.log(selector.length); // 4

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Abi } from '@tevm/voltaire/Abi';
import { Hex } from '@tevm/voltaire/Hex';

// Build transaction calldata
const selector = Keccak256.selector('transfer(address,uint256)');
const params = Abi.encodeParams(
  ['address', 'uint256'],
  [recipient, amount]
);

// Combine selector + encoded params
const calldata = new Uint8Array(selector.length + params.length);
calldata.set(selector, 0);
calldata.set(params, selector.length);

console.log(Hex.fromBytes(calldata));
// 0xa9059cbb000000000000000000000000...

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// ERC20 selectors
const transfer = Keccak256.selector('transfer(address,uint256)');
console.assert(Hex.fromBytes(transfer) === '0xa9059cbb');

const approve = Keccak256.selector('approve(address,uint256)');
console.assert(Hex.fromBytes(approve) === '0x095ea7b3');

const balanceOf = Keccak256.selector('balanceOf(address)');
console.assert(Hex.fromBytes(balanceOf) === '0x70a08231');

// ERC721 selectors
const safeTransferFrom = Keccak256.selector('safeTransferFrom(address,address,uint256)');
console.assert(Hex.fromBytes(safeTransferFrom) === '0x42842e0e');

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// Build selector registry
const selectorRegistry = new Map<string, string>([
  [Hex.fromBytes(Keccak256.selector('transfer(address,uint256)')), 'transfer(address,uint256)'],
  [Hex.fromBytes(Keccak256.selector('approve(address,uint256)')), 'approve(address,uint256)'],
  [Hex.fromBytes(Keccak256.selector('balanceOf(address)')), 'balanceOf(address)'],
]);

// Decode calldata
const calldata = '0xa9059cbb000...';
const selector = calldata.slice(0, 10); // First 4 bytes (0x + 8 hex chars)
const signature = selectorRegistry.get(selector);
console.log(signature); // "transfer(address,uint256)"

Technical Notes:

Returns first 4 bytes of Keccak256.hashString(signature)
Signature format: functionName(type1,type2,...) (no spaces, no param names)
Canonical types required: uint256 not uint, address not address payable
Case-sensitive - Transfer ≠ transfer

Signature normalization critical:

✅ "transfer(address,uint256)" - Correct
❌ "transfer(address, uint256)" - Space causes different selector
❌ "transfer(address to, uint256 amount)" - Param names cause different selector
❌ "transfer(address,uint)" - Use canonical uint256

topic(signature)

Compute event topic (32-byte Keccak256 hash). Signature:

function topic(signature: string): Keccak256Hash

Parameters:

signature (string) - Event signature (e.g., "Transfer(address,address,uint256)")

Returns: Keccak256Hash (32 bytes) - Event topic hash Throws: Never throws for valid signature string

Basic Usage
Event Filtering
Common Topics
Topic Decoding

import { Keccak256 } from '@tevm/voltaire/Keccak256';

const topic = Keccak256.topic('Transfer(address,address,uint256)');
// Uint8Array(32) [full 32-byte hash]

console.log(topic.length); // 32

import { Keccak256 } from '@tevm/voltaire/Keccak256';

// Filter logs for Transfer events
const transferTopic = Keccak256.topic('Transfer(address,address,uint256)');

const logs = await provider.getLogs({
  address: tokenAddress,
  topics: [transferTopic], // Filter by topic0
  fromBlock: startBlock,
  toBlock: endBlock
});

// All logs will be Transfer events

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// ERC20 events
const transfer = Keccak256.topic('Transfer(address,address,uint256)');
console.assert(
  Hex.fromBytes(transfer) ===
  '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef'
);

const approval = Keccak256.topic('Approval(address,address,uint256)');
console.assert(
  Hex.fromBytes(approval) ===
  '0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925'
);

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// Build topic registry
const topicRegistry = new Map<string, string>([
  [Hex.fromBytes(Keccak256.topic('Transfer(address,address,uint256)')), 'Transfer'],
  [Hex.fromBytes(Keccak256.topic('Approval(address,address,uint256)')), 'Approval'],
]);

// Decode log event
const log = {
  topics: [
    '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
    '0x000000000000000000000000742d35cc6634c0532925a3b844bc9e7595f51e3e',
    '0x000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045'
  ],
  data: '0x0000000000000000000000000000000000000000000000000de0b6b3a7640000'
};

const eventName = topicRegistry.get(log.topics[0]);
console.log(eventName); // "Transfer"

Technical Notes:

Returns full 32 bytes (unlike selector which returns 4 bytes)
Used as topics[0] in Ethereum event logs
Indexed event parameters become additional topics (topics[1], topics[2], etc.)
Non-indexed parameters in log data field

Event Log Structure:

interface Log {
  topics: string[];  // [topic0=eventHash, topic1=indexed1, topic2=indexed2, ...]
  data: string;      // ABI-encoded non-indexed parameters
}

contractAddress(sender, nonce)

Compute contract address from deployer and nonce (CREATE opcode). Signature:

function contractAddress(sender: Uint8Array, nonce: bigint): Uint8Array

Parameters:

sender (Uint8Array) - Deployer address (20 bytes)
nonce (bigint) - Transaction nonce

Returns: Uint8Array (20 bytes) - Contract address Throws:

InvalidLengthError - Sender not 20 bytes

Basic Usage
Predicting Deployment
Contract Factory
Reverse Lookup

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';

const deployer = Address('0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e');
const nonce = 5n;

const contractAddr = Keccak256.contractAddress(deployer, nonce);
console.log(contractAddr.length); // 20

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';

// Predict contract address before deployment
async function predictContractAddress(
  deployer: Uint8Array
): Promise<Uint8Array> {
  // Get current nonce
  const nonce = await provider.getTransactionCount(deployer);

  // Calculate next contract address
  return Keccak256.contractAddress(deployer, BigInt(nonce));
}

const nextContract = await predictContractAddress(deployerAddress);
console.log('Next deployment will create contract at:', nextContract);

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';

// Track factory deployments
const factory = Address('0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e');
let nonce = 0n;

function getNextContractAddress(): Uint8Array {
  const addr = Keccak256.contractAddress(factory, nonce);
  nonce++;
  return addr;
}

const contract1 = getNextContractAddress(); // nonce 0
const contract2 = getNextContractAddress(); // nonce 1
const contract3 = getNextContractAddress(); // nonce 2

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';
import { Hex } from '@tevm/voltaire/Hex';

// Find which nonce created a contract
function findDeploymentNonce(
  deployer: Uint8Array,
  targetContract: Uint8Array,
  maxNonce: bigint = 1000n
): bigint | null {
  for (let nonce = 0n; nonce <= maxNonce; nonce++) {
    const addr = Keccak256.contractAddress(deployer, nonce);
    if (Hex.fromBytes(addr) === Hex.fromBytes(targetContract)) {
      return nonce;
    }
  }
  return null;
}

Algorithm:

address = keccak256(rlp([sender, nonce]))[12:]

Technical Notes:

Formula defined in Ethereum Yellow Paper
RLP encoding: [sender, nonce] where sender is 20 bytes, nonce is minimal big-endian
Last 20 bytes of hash become contract address
Nonce increments with each transaction from sender
Deterministic - same sender + nonce always produces same address

create2Address(deployer, salt, initCodeHash)

Compute contract address using CREATE2 opcode (EIP-1014). Signature:

function create2Address(
  deployer: Uint8Array,
  salt: Uint8Array,
  initCodeHash: Uint8Array
): Uint8Array

Parameters:

deployer (Uint8Array) - Deployer address (20 bytes)
salt (Uint8Array) - 32-byte salt
initCodeHash (Uint8Array) - 32-byte hash of initialization code

Returns: Uint8Array (20 bytes) - Contract address Throws:

InvalidLengthError - Deployer not 20 bytes
InvalidLengthError - Salt not 32 bytes
InvalidLengthError - initCodeHash not 32 bytes

Basic Usage
Deterministic Deployment
Minimal Proxy (EIP-1167)
Salt Generation

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';
import { Bytes32 } from '@tevm/voltaire/Bytes32';
import { Bytecode } from '@tevm/voltaire/Bytecode';

const deployer = Address('0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e');
const salt = Bytes32('0x0000000000000000000000000000000000000000000000000000000000000001');
const initCode = Bytecode('0x60806040...');
const initCodeHash = Keccak256.hash(initCode);

const contractAddr = Keccak256.create2Address(deployer, salt, initCodeHash);
console.log(contractAddr.length); // 20

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';
import { Bytes32 } from '@tevm/voltaire/Bytes32';

// Compute address before deployment
function getCreate2Address(
  factory: Uint8Array,
  salt: Uint8Array,
  bytecode: Uint8Array
): Uint8Array {
  const initCodeHash = Keccak256.hash(bytecode);
  return Keccak256.create2Address(factory, salt, initCodeHash);
}

// Deploy contract to predetermined address
const factory = Address('0x4e59b44847b379578588920ca78fbf26c0b4956c'); // CREATE2 factory
const salt = Bytes32('0x' + '0'.repeat(64)); // Zero salt
const bytecode = Bytecode('0x60806040...');

const predictedAddr = getCreate2Address(factory, salt, bytecode);
console.log('Will deploy to:', predictedAddr);

// Deploy - address will match prediction
await deployContract(factory, salt, bytecode);

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';
import { Bytes32 } from '@tevm/voltaire/Bytes32';
import { Hex } from '@tevm/voltaire/Hex';

// Predict minimal proxy address
function predictProxyAddress(
  factory: Uint8Array,
  implementation: Uint8Array,
  salt: Uint8Array
): Uint8Array {
  // EIP-1167 minimal proxy bytecode
  const proxyBytecode = Hex.toBytes(
    '0x3d602d80600a3d3981f3363d3d373d3d3d363d73' +
    Hex.fromBytes(implementation).slice(2) +
    '5af43d82803e903d91602b57fd5bf3'
  );

  const initCodeHash = Keccak256.hash(proxyBytecode);
  return Keccak256.create2Address(factory, salt, initCodeHash);
}

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Bytes32 } from '@tevm/voltaire/Bytes32';

// Generate deterministic salt from parameters
function generateSalt(owner: Uint8Array, version: number): Uint8Array {
  const data = new Uint8Array(20 + 8);
  data.set(owner, 0);
  new DataView(data.buffer).setBigUint64(20, BigInt(version), false);
  return Keccak256.hash(data);
}

// Use salt for CREATE2
const salt = generateSalt(ownerAddress, 1);
const addr = Keccak256.create2Address(factory, salt, initCodeHash);

Algorithm:

address = keccak256(0xff ++ deployer ++ salt ++ keccak256(initCode))[12:]

Technical Notes:

Defined in EIP-1014
Enables deterministic deployment independent of nonce
Same deployer + salt + initCode always produces same address
0xff prefix distinguishes from CREATE (prevents collision)
initCode hashed separately (allows large bytecode)
Commonly used for counterfactual instantiation, proxy factories

Comparison with CREATE:

Feature	CREATE	CREATE2
Depends on nonce	Yes	No
Depends on initCode	Indirectly (via nonce)	Yes (hashed)
Predictable	Requires knowing nonce	Always predictable
Redeployable	No (nonce increments)	No (same address)
Use case	Normal deployment	Counterfactual, upgradeable proxies

Usage Examples

Full Contract Deployment Flow

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Address } from '@tevm/voltaire/Address';
import { Bytes32 } from '@tevm/voltaire/Bytes32';
import { Bytecode } from '@tevm/voltaire/Bytecode';

// 1. Predict CREATE address
const deployer = Address('0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e');
const currentNonce = await provider.getTransactionCount(deployer);
const createAddr = Keccak256.contractAddress(deployer, BigInt(currentNonce));

// 2. Predict CREATE2 address
const factory = Address('0x4e59b44847b379578588920ca78fbf26c0b4956c');
const salt = Bytes32('0x0000000000000000000000000000000000000000000000000000000000000001');
const initCode = Bytecode('0x60806040...');
const initCodeHash = Keccak256.hash(initCode);
const create2Addr = Keccak256.create2Address(factory, salt, initCodeHash);

console.log('CREATE address:', createAddr);
console.log('CREATE2 address:', create2Addr);

Function Call Decoding

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// Decode transaction calldata
const calldata = '0xa9059cbb000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa960450000000000000000000000000000000000000000000000000de0b6b3a7640000';

// Extract selector
const selector = calldata.slice(0, 10);

// Compare with known selectors
const transferSel = Hex.fromBytes(Keccak256.selector('transfer(address,uint256)'));

if (selector === transferSel) {
  console.log('This is a transfer call');
  // Decode parameters from calldata.slice(10)
}

Event Log Processing

import { Keccak256 } from '@tevm/voltaire/Keccak256';
import { Hex } from '@tevm/voltaire/Hex';

// Process Transfer event logs
const transferTopic = Hex.fromBytes(
  Keccak256.topic('Transfer(address,address,uint256)')
);

const logs = await provider.getLogs({
  topics: [transferTopic],
  fromBlock: 0,
  toBlock: 'latest'
});

for (const log of logs) {
  console.log('Transfer event:');
  console.log('From:', log.topics[1]); // indexed from address
  console.log('To:', log.topics[2]);   // indexed to address
  console.log('Amount:', log.data);    // non-indexed amount
}

Core Hashing Methods - Basic hash, hashString, hashHex
Usage Patterns - Common patterns and best practices
Implementations - Implementation comparison
ABI Module - ABI encoding/decoding for selectors and topics

Overview

Getting Started

Core Concepts

Skills

JSONRPCProvider

Contract

Primitives

Cryptography

EVM

Utils

Guides

Examples

Swift

Zig

Developer Documentation

Generated API (TypeDoc)

Ethereum Methods

Try it Live

Ethereum Methods

selector(signature)

topic(signature)

contractAddress(sender, nonce)

create2Address(deployer, salt, initCodeHash)

Usage Examples

Full Contract Deployment Flow

Function Call Decoding

Event Log Processing

Overview

Getting Started

Core Concepts

Skills

JSONRPCProvider

Contract

Primitives

Cryptography

EVM

Utils

Guides

Examples

Swift

Zig

Developer Documentation

Generated API (TypeDoc)

Try it Live

​Ethereum Methods

​selector(signature)

​topic(signature)

​contractAddress(sender, nonce)

​create2Address(deployer, salt, initCodeHash)

​Usage Examples

​Full Contract Deployment Flow

​Function Call Decoding

​Event Log Processing

​Related

Ethereum Methods

selector(signature)

topic(signature)

contractAddress(sender, nonce)

create2Address(deployer, salt, initCodeHash)

Usage Examples

Full Contract Deployment Flow

Function Call Decoding

Event Log Processing

Related