@ethereumjs/rlp

What is @ethereumjs/rlp?

@ethereumjs/rlp is a JavaScript library for encoding and decoding data using Recursive Length Prefix (RLP) encoding, which is a serialization method used in the Ethereum protocol. This package is part of the EthereumJS project and is commonly used for handling Ethereum data structures.

What are @ethereumjs/rlp's main functionalities?

RLP Encoding

This feature allows you to encode data into RLP format. In the code sample, an array containing the strings 'cat' and 'dog' is encoded into RLP.

const rlp = require('@ethereumjs/rlp');
const encoded = rlp.encode(['cat', 'dog']);
console.log(encoded);

RLP Decoding

This feature allows you to decode RLP-encoded data back into its original form. In the code sample, the previously encoded array is decoded back to ['cat', 'dog'].

const rlp = require('@ethereumjs/rlp');
const encoded = rlp.encode(['cat', 'dog']);
const decoded = rlp.decode(encoded);
console.log(decoded);

Other packages similar to @ethereumjs/rlp

rlp

The 'rlp' package is another library for encoding and decoding data using RLP. It is simpler and more lightweight compared to @ethereumjs/rlp, but it offers similar functionality for basic RLP operations.

ethereumjs-util

The 'ethereumjs-util' package provides a variety of utility functions for Ethereum, including RLP encoding and decoding. It is more comprehensive than @ethereumjs/rlp, offering additional utilities for handling Ethereum addresses, signatures, and more.

README

@ethereumjs/rlp v10

Recursive Length Prefix encoding for Node.js and the browser.

Table of Contents

• Installation
• Usage
• Browser
• API
• CLI
• EthereumJS
• License

Installation

To obtain the latest version, simply require the project using npm:

npm install @ethereumjs/rlp

Install with -g if you want to use the CLI.

Usage

// ./examples/simple.ts

import { RLP } from '@ethereumjs/rlp'
import assert from 'assert'

const nestedList = [[], [[]], [[], [[]]]]
const encoded = RLP.encode(nestedList)
const decoded = RLP.decode(encoded)
assert.deepStrictEqual(decoded, nestedList, 'decoded output does not match original')
console.log('assert.deepStrictEqual would have thrown if the decoded output did not match')

Browser

We provide hybrid ESM/CJS builds for all our libraries. With the v10 breaking release round from Spring 2025, all libraries are "pure-JS" by default and we have eliminated all hard-wired WASM code. Additionally we have substantially lowered the bundle sizes, reduced the number of dependencies, and cut out all usages of Node.js-specific primitives (like the Node.js event emitter).

It is easily possible to run a browser build of one of the EthereumJS libraries within a modern browser using the provided ESM build. For a setup example see ./examples/browser.html.

API

RLP.encode(plain) - RLP encodes an Array, Uint8Array or String and returns a Uint8Array.

RLP.decode(encoded, [stream=false]) - Decodes an RLP encoded Uint8Array, Array or String and returns a Uint8Array or NestedUint8Array. If stream is enabled, it will just decode the first rlp sequence in the Uint8Array. By default, it would throw an error if there are more bytes in Uint8Array than used by the rlp sequence.

CLI

rlp encode <JSON string>
rlp decode <0x-prefixed hex string>

Examples

• rlp encode '5' -> 0x05
• rlp encode '[5]' -> 0xc105
• rlp encode '["cat", "dog"]' -> 0xc88363617483646f67
• rlp decode 0xc88363617483646f67 -> ["cat","dog"]

EthereumJS

See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices. If you want to join for work or carry out improvements on the libraries, please review our contribution guidelines first.

License

MPL-2.0