Rlp.encodeArray

Encode array of values to RLP format

Try it Live

Run RLP examples in the interactive playground

encodeArray vs encodeList

encodeArray is functionally identical to encodeList - it’s provided as an alias for semantic clarity:

import { Rlp } from 'tevm'

const items = [new Uint8Array([1]), new Uint8Array([2])]

// These are equivalent
const encoded1 = Rlp.encodeArray(items)
const encoded2 = Rlp.encodeList(items)
// Both => Uint8Array([0xc4, 0x01, 0x02])

Use encodeArray when thinking of the input as an array of values (e.g., transaction fields, block components).

Use encodeList when thinking of the input as a list structure (e.g., nested lists, tree structures).

Usage Patterns

Transaction Encoding

Encode transaction fields as array:

import { Rlp } from 'tevm'

interface LegacyTx {
  nonce: bigint
  gasPrice: bigint
  gasLimit: bigint
  to: Uint8Array
  value: bigint
  data: Uint8Array
  v: bigint
  r: Uint8Array
  s: Uint8Array
}

function encodeLegacyTx(tx: LegacyTx): Uint8Array {
  const fields = [
    bigintToBytes(tx.nonce),
    bigintToBytes(tx.gasPrice),
    bigintToBytes(tx.gasLimit),
    tx.to,
    bigintToBytes(tx.value),
    tx.data,
    bigintToBytes(tx.v),
    tx.r,
    tx.s
  ]

  return Rlp.encodeArray(fields)
}

const tx: LegacyTx = {
  nonce: 0n,
  gasPrice: 20000000000n,
  gasLimit: 21000n,
  to: new Uint8Array(20).fill(0x01),
  value: 1000000000000000000n,
  data: Bytes(),
  v: 27n,
  r: Bytes32().fill(0x02),
  s: Bytes32().fill(0x03)
}

const encoded = encodeLegacyTx(tx)

Block Header Encoding

Encode block header fields:

import { Rlp } from 'tevm'

interface BlockHeader {
  parentHash: Uint8Array
  uncleHash: Uint8Array
  coinbase: Uint8Array
  stateRoot: Uint8Array
  transactionsRoot: Uint8Array
  receiptsRoot: Uint8Array
  logsBloom: Uint8Array
  difficulty: bigint
  number: bigint
  gasLimit: bigint
  gasUsed: bigint
  timestamp: bigint
  extraData: Uint8Array
}

function encodeBlockHeader(header: BlockHeader): Uint8Array {
  const fields = [
    header.parentHash,
    header.uncleHash,
    header.coinbase,
    header.stateRoot,
    header.transactionsRoot,
    header.receiptsRoot,
    header.logsBloom,
    bigintToBytes(header.difficulty),
    bigintToBytes(header.number),
    bigintToBytes(header.gasLimit),
    bigintToBytes(header.gasUsed),
    bigintToBytes(header.timestamp),
    header.extraData
  ]

  return Rlp.encodeArray(fields)
}

Log Entry Encoding

Encode event log entries:

import { Rlp } from 'tevm'

interface Log {
  address: Uint8Array
  topics: Uint8Array[]
  data: Uint8Array
}

function encodeLog(log: Log): Uint8Array {
  const fields = [
    log.address,
    log.topics,  // Nested array
    log.data
  ]

  return Rlp.encodeArray(fields)
}

const log: Log = {
  address: new Uint8Array(20).fill(0x01),
  topics: [
    Bytes32().fill(0x02),
    Bytes32().fill(0x03)
  ],
  data: new Uint8Array([0x04, 0x05, 0x06])
}

const encoded = encodeLog(log)

Receipt Encoding

Encode transaction receipts:

import { Rlp } from 'tevm'

interface Receipt {
  status: bigint
  gasUsed: bigint
  logsBloom: Uint8Array
  logs: Log[]
}

function encodeReceipt(receipt: Receipt): Uint8Array {
  const encodedLogs = receipt.logs.map(log => encodeLog(log))

  const fields = [
    bigintToBytes(receipt.status),
    bigintToBytes(receipt.gasUsed),
    receipt.logsBloom,
    encodedLogs
  ]

  return Rlp.encodeArray(fields)
}

Merkle Patricia Trie Node

Encode trie nodes:

import { Rlp } from 'tevm'

type TrieNode =
  | { type: 'branch'; children: Uint8Array[]; value: Uint8Array }
  | { type: 'extension'; path: Uint8Array; child: Uint8Array }
  | { type: 'leaf'; path: Uint8Array; value: Uint8Array }

function encodeTrieNode(node: TrieNode): Uint8Array {
  if (node.type === 'branch') {
    // Branch node: [child0, child1, ..., child15, value]
    return Rlp.encodeArray([...node.children, node.value])
  }

  if (node.type === 'extension') {
    // Extension node: [path, child]
    return Rlp.encodeArray([node.path, node.child])
  }

  // Leaf node: [path, value]
  return Rlp.encodeArray([node.path, node.value])
}

Schema-based Encoding

Define typed schemas for RLP encoding:

import { Rlp } from 'tevm'

// Define schema
interface AccountState {
  nonce: bigint
  balance: bigint
  storageRoot: Uint8Array
  codeHash: Uint8Array
}

// Encoder function
function encodeAccountState(account: AccountState): Uint8Array {
  return Rlp.encodeArray([
    bigintToBytes(account.nonce),
    bigintToBytes(account.balance),
    account.storageRoot,
    account.codeHash
  ])
}

// Decoder function (see decodeArray)
function decodeAccountState(bytes: Uint8Array): AccountState {
  const arr = Rlp.decodeArray(bytes)
  return {
    nonce: bytesToBigint(arr[0]),
    balance: bytesToBigint(arr[1]),
    storageRoot: arr[2],
    codeHash: arr[3]
  }
}

Performance

Pre-calculate Sizes

Calculate total size before encoding:

import { Rlp } from 'tevm'

const items = [
  new Uint8Array([1, 2, 3]),
  new Uint8Array([4, 5, 6])
]

// Calculate size first
const size = Rlp.getEncodedLength(items)
console.log(`Array will encode to ${size} bytes`)

// Then encode
const encoded = Rlp.encodeArray(items)

Batch Encoding

Encode multiple arrays efficiently:

import { Rlp } from 'tevm'

const transactions = [
  [nonce1, gasPrice1, ...],
  [nonce2, gasPrice2, ...],
  [nonce3, gasPrice3, ...]
]

// Encode each transaction
const encodedTxs = transactions.map(tx => Rlp.encodeArray(tx))

// Encode as list of transactions
const block = Rlp.encodeArray(encodedTxs)

Reusable Buffers

For high-frequency encoding, consider pre-allocating buffers:

import { Rlp } from 'tevm'

class TxEncoder {
  private buffer = new Uint8Array(1024)  // Reusable buffer

  encode(tx: Transaction): Uint8Array {
    const fields = [
      bigintToBytes(tx.nonce),
      bigintToBytes(tx.gasPrice),
      // ...
    ]

    return Rlp.encodeArray(fields)
  }
}

See Also

• encode - Universal encoder
• encodeList - Encode list
• decodeArray - Decode to array
• encodeObject - Encode object
• Algorithm - RLP specification