ethereumjs-util

What is ethereumjs-util?

The ethereumjs-util package provides a set of utility functions for Ethereum. These utilities include functions for handling addresses, big numbers, hashing, and encoding/decoding data according to the Ethereum protocol standards. It is a foundational package that can be used to develop Ethereum-based applications, facilitating tasks such as transaction formatting, signature verification, and data conversion.

What are ethereumjs-util's main functionalities?

Address Formatting

Converts an Ethereum address to its checksummed version to prevent case sensitivity errors.

const { toChecksumAddress } = require('ethereumjs-util');
const checksumAddress = toChecksumAddress('0xfb6916095ca1df60bb79ce92ce3ea74c37c5d359');
console.log(checksumAddress);

Hashing

Generates a keccak256 hash of the input data, a common hashing function used in Ethereum.

const { keccak256 } = require('ethereumjs-util');
const hash = keccak256(Buffer.from('hello'));
console.log('Hash:', hash.toString('hex'));

Signature Verification

Signs a message hash with a private key and serializes the signature in a format compatible with RPC calls.

const { ecsign, toRpcSig } = require('ethereumjs-util');
const privateKey = Buffer.from('c87509a1c067bbde7aebb4d3c0a0b8ab8bd02b676c91662b5f41c4ec9863d8ee', 'hex');
const msgHash = keccak256(Buffer.from('hello'));
const sig = ecsign(msgHash, privateKey);
const serializedSig = toRpcSig(sig.v, sig.r, sig.s);
console.log('Signature:', serializedSig);

Other packages similar to ethereumjs-util

web3

Web3 is a comprehensive Ethereum library that includes utilities similar to ethereumjs-util but also provides a wide range of functionalities to interact with Ethereum nodes directly. It covers the entire Ethereum API and is more extensive for building DApps.

ethers

Ethers is a lightweight library that aims to be a complete and compact library for interacting with the Ethereum Blockchain and its ecosystem. It includes utilities for addresses, big numbers, and hashing, similar to ethereumjs-util, but also features a complete set of functions to interact with smart contracts and blockchain data.

README

SYNOPSIS

or #ethereumjs on freenode

A collection of utility functions for ethereum. It can be used in node.js or can be in the browser with browserify.

API

properties

• MAX_INTEGER - The max interger that the VM can handle
• TWO_POW256 - 2^256
• SHA3_NULL - SHA3-256 hash of null
• SHA3_RLP_ARRAY - SHA3-256 of an rlp of an empty array
• SHA3_RLP - SHA3-256 hash of the rlp of null
• ETH_UNITS - an array of ethereum units
• BN
• rlp

methods

zeros(number)

Returns buffer filled with 0's
Parameters

• number - the number bytes to to return

Return: buffer

pad(val, length)

pads an array or buffer with leading zeros till it has length bytes
Parameters

• val - the value to pad
• length - the of the resulting value

Return: array or buffer

rpad(val, length)

pads an array or buffer with trailing zeros till it has length bytes
Parameters

• val - the value to pad
• length - the of the resulting value

Return: array or buffer

unpad(val)

Trims leading zeros from a buffer or an array
Parameters

• val - a buffer or and Array to unpad

Return: buffer or and Array

toBufer(val)

Attemps to turn a value into a Buffer
Parameters

• val the

Return: Buffer

intToHex(int)

Converts an Integer into a hex String
Parameters

• int

Return: String

intToBuffer(int)

Converts an Integer to a Buffer
Parameters

• int

Return: Buffer

bufferToInt(buf)

converts a Buffer to an Interger
Parameters

• buf

Return: Interger

fromSigned(buf)

interpets a Buffer as a signed Integer
Parameters

• buf

Return: BN.js

toUnsigned(num)

Converts a BN.js to an unsigned interger
Parameters

• num - a BN.js

Return: buffer

publicToAddress(pubKey)

Returns the ethereum address of a given public key
Parameters

• pubKey - the public key as a buffer

Return: : buffer

privateToAddress(privateKey)

Returns the ethereum address of a given private key
Parameters

• privateKey - the private key as a buffer

Return: Buffer

privateToPublic(privateKey)

Returns the ethereum public key of a given private key
Parameters

• privateKey - the private key as a buffer

Return: Buffer

generateAddress(from, nonce)

Generates an address of a newly created contract. Don't forget to incerment the nonce to get the correct address.
Parameters

• from - the address of the account creating the contract
• nonce - the creating accounts nonce

Return: Buffer

sha3(a, bytes)

Returns a sha3 of a of the length of bytes
Parameters

• a the value to hash
• bytes how many bytes the hash should be

Return: Buffer

printBA(ba)

Print a Buffer Array
Parameters

• ba - an Array of Buffers

Return: a Buffer Array

baToJSON(ba)

converts a buffer array to JSON
Parameters

• ba - an Array of Buffers

Return: a JSON Object

isHexPrefixed(String)

Returns a Boolean on whether or not the a sting starts with 0x
Parameters

• String - a String

Return: String

stripHexPrefix(String)

Removes 0x from a given String
Parameters

• String - a String

Return: String

addHexPrefix(String)

Adds 0x to a given string if it does not already start with 0x
Parameters

• string

Return: string

defineProperties(self, fields)

defines properties on a Object. It make the assumtion that underlying data is binary. Parameters

• self - the Object to define properties on
• fields - an array fields to define. Fields can contain
• name the name of the properties
• length the number of bytes the field can have
• allowLess if the field can be less than the length
• allowEmpty

validate(fields, data)

Validate defined fields
Parameters

• fields
• data

Return: Boolean

TESTING

Node.js Tests use Mocha. Test in the browser use Testling.

LICENSE

MPL-2.0