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Utils.md

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Utils

Helpers to manage Farcaster Messages.

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

HubErrorCode defines all the types of errors that can be raised in the Hub.

Hub Error Codes

Name Description
unauthenticated The request lacks valid authentication credentials. Retry with credentials.
unauthorized The authenticated request lacks the authority to perform this action.
bad_request The request cannot be completed as constructed. Do not retry.
bad_request.parse_failure The request failed to parse. Do not retry.
bad_request.invalid_param The request contains an invalid parameter. Do not retry.
bad_request.validation_failure The request failed validation. Do not retry.
bad_request.duplicate The request contains a duplicate entry. Do not retry.
bad_request.conflict The request conflicts with an existing resource. Do not retry.
not_found The requested resource could not be found.
not_implemented The request cannot be completed because the operation is not executable.
not_implemented.deprecated The requested operation is deprecated.
unavailable The request cannot be completed, and it may or may not be safe to retry.
unavailable.network_failure The request failed due to a network failure, and it may be safe to retry.
unavailable.storage_failure The request failed due to a storage failure, and it may be safe to retry.
unknown An unknown error was encountered.

Time

Farcaster timestamps are counted as seconds 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 following this equation:
Farcaster Time (seconds) = (Unix Time (milliseconds) / 1000) - 1609459200

getFarcasterTime

Returns the current time in seconds 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 seconds as a Farcaster timestamp.

toFarcasterTime

Converts a Unix milliseconds timestamp to a Farcaster seconds 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 seconds 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 seconds timestamp to a Unix milliseconds timestamp.

Usage

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

const timestamp = 70160902; // Farcaster timestamp in seconds
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 seconds 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 Ethereum 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.