hub-monorepo/packages/hub-nodejs/docs/Utils.md

Utils

Helpers to manage Farcaster Messages.

• Bytes
  • bytesToHexString
  • hexStringToBytes
  • bytesToUTF8String
• Errors
  • HubError
  • HubErrorCodes
• Time
  • getFarcasterTime
  • toFarcasterTime
  • fromFarcasterTime
• Verifications
  • makeVerificationEthAddressClaim

Bytes

Farcaster stores addresses, keys and signatures as binary data held in Uint8Arrays. Converting such values to hex strings or utf-8 strings is useful when calling other libraries or displaying strings to users.

bytesToHexString

Returns a hex string from a bytes array.

Usage

import { bytesToHexString } from '@farcaster/hub-nodejs';

// Safety: byteArray is known and can't error
const byteArray = new Uint8Array([1, 2, 3]); // can be bytes signature, address, etc
const hexString = bytesToHexString(byteArray)._unsafeUnwrap();
console.log(hexString); // "0x010203"

Returns

Value	Description
HubResult<string>	A hex string representation of the input byte array.

Parameters

Name	Type	Description
bytes	Uint8Array	The input byte array to convert into a hex string.

---

hexStringToBytes

Returns a bytes array from a hex string.

Usage

import { hexStringToBytes } from '@farcaster/hub-nodejs';

// Safety: hexString is known and can't error
const hexString = '0x010203'; // can be signature, address, etc
const byteArray = hexStringToBytes(hexString)._unsafeUnwrap();
console.log(byteArray); // Uint8Array [1, 2, 3]

Returns

Value	Description
HubResult<Uint8Array>	A byte array representation of the input hexadecimal string.

Parameters

Name	Type	Description
hex	string	The hexadecimal string to convert into an output byte array.

---

bytesToUTF8String

Returns a UTF-8 string from a bytes array.

import { bytesToUtf8String } from './utils';

// Safety: byteArray is known and can't error
const byteArray = new Uint8Array([72, 101, 108, 108, 111]); // "Hello" in ASCII encoding.
const utfEncodedStr = bytesToUtf8String(byteArray)._unsafeUnwrap();
console.log(utfEncodedStr); //"Hello"

Returns

Value	Description
HubResult<string>	A UTF-8 string representation of the input byte array.

Parameters

Name	Type	Description
bytes	Uint8Array	The input byte array to convert into a hex string.

Errors

Error handling in @farcaster/hub-nodejs is monadic and functions do not throw exceptions. Each function call returns a Result object which contains a success value or error value. Read the neverthrow documentation to learn about handling Result types.

Hub Error

TODO

Hub Error Codes

Name	Description
unauthenticated	TODO
unauthorized	TODO
bad_request	TODO
bad_request.parse_failure	TODO
bad_request.invalid_param	TODO
bad_request.validation_failure	TODO
bad_request.duplicate	TODO
bad_request.conflict	TODO
not_found	TODO
not_implemented	TODO
not_implemented.deprecated	TODO
unavailable	TODO
unavailable.network_failure	TODO
unavailable.storage_failure	TODO
unknown	TODO

Time

Farcaster timestamps are counted as milliseconds since the Farcaster epoch, which began on Jan 1, 2021 00:00:00 UTC.

Using a more recent epoch lets Farcaster use shorter 32-bit values to hold times which reduces the size of messages. Timestamps are usually measured as milliseconds since the Unix epoch and can be converted to Farcaster time by subtracting 1609459200000.

getFarcasterTime

Returns the current time in milliseconds as a Farcaster timestamp.

Usage

import { getFarcasterTime } from '@farcaster/hub-nodejs';

const timestamp = getFarcasterTime()._unsafeUnwrap();
console.log(timestamp); // 70117755

Returns

Value	Description
HubResult<number>	The current time in milliseconds as a Farcaster timestamp.

---

toFarcasterTime

Converts a Unix milliseconds timestamp to a Farcaster milliseconds timestamp.

Usage

import { toFarcasterTime } from '@farcaster/hub-nodejs';

const msTimestamp = Date.now(); // can be anything, e.g., ethereum transaction timestamp
const timestamp = toFarcasterTime(msTimestamp)._unsafeUnwrap();
console.log(timestamp); // 70117500

Returns

Value	Description
HubResult<number>	The converted time in milliseconds as a Farcaster timestamp.

Parameters

Name	Type	Description
time	number	The Unix timestamp in milliseconds to convert to a Farcaster timestamp.

---

fromFarcasterTime

Converts a Farcaster milliseconds timestamp to a Unix milliseconds timestamp.

Usage

import { fromFarcasterTime } from '@farcaster/hub-nodejs';

const timestamp = 70160902; // Farcaster timestamp in milliseconds
const msTimestamp = fromFarcasterTime(timestamp)._unsafeUnwrap();
console.log(msTimestamp); // 1679620102000

Returns

Value	Description
HubResult<number>	The converted time in milliseconds as a Unix timestamp.

Parameters

Name	Type	Description
time	number	The Farcaster timestamp in milliseconds to convert to a Unix timestamp.

Verifications

makeVerificationEthAddressClaim

Usage

import {
  EthersEip712Signer,
  FarcasterNetwork,
  hexStringToBytes,
  makeVerificationEthAddressClaim,
} from '@farcaster/hub-nodejs';
import { Wallet } from 'ethers';

// Create a valid Eip712Signer from the Etherum Address making the claim
const mnemonic = 'ordinary long coach bounce thank quit become youth belt pretty diet caught attract melt bargain';
const wallet = Wallet.fromPhrase(mnemonic);
const eip712Signer = new EthersEip712Signer(wallet);

// Construct the claim object with the block number of a recent block
const blockHashHex = '0x1d3b0456c920eb503450c7efdcf9b5cf1f5184bf04e5d8ecbcead188a0d02018';
const blockHashBytes = hexStringToBytes(blockHashHex)._unsafeUnwrap(); // Safety: blockHashHex is known and can't error

const addressBytes = (await eip712Signer.getSignerKey())._unsafeUnwrap(); // Safety: eip712Signer is known and can't error
const claimResult = makeVerificationEthAddressClaim(1, addressBytes, FarcasterNetwork.DEVNET, blockHashBytes);

Returns

Value	Description
HubResult<VerificationEthAddressClaim>	VerificationEthAddressClaim object that can be submitted to Hubs.

Parameters

Name	Type	Description
fidNumber	number	The Farcaster ID to verify.
ethAddress	Uint8Array	The Ethereum address to verify.
network	FarcasterNetwork	The Farcaster network value as defined in protobuf.
blockHash	Uint8Array	The hash of a recent Ethereum block.