Utilities API

Low-level utility functions for encoding and PNG operations.

encodeBase64()

Encode bytes to Base64 string.

Signature:

function encodeBase64(bytes: Uint8Array): string

Parameters:

Returns: string — Base64-encoded string.

Example:

import { encodeBase64 } from '@motioneffector/cards'

const bytes = new Uint8Array([72, 101, 108, 108, 111])
const base64 = encodeBase64(bytes)
// "SGVsbG8="

decodeBase64()

Decode Base64 string to bytes.

Signature:

function decodeBase64(base64: string): Uint8Array

Parameters:

Returns: Uint8Array — Decoded bytes.

Example:

import { decodeBase64 } from '@motioneffector/cards'

const bytes = decodeBase64('SGVsbG8=')
// Uint8Array [72, 101, 108, 108, 111]

Throws:

• Error — When the input is not valid Base64

computeCRC32()

Compute CRC-32 checksum for PNG chunk validation.

Signature:

function computeCRC32(type: Uint8Array, data: Uint8Array): number

Parameters:

Returns: number — CRC-32 checksum as unsigned 32-bit integer.

Example:

import { computeCRC32 } from '@motioneffector/cards'

const type = new Uint8Array([116, 69, 88, 116]) // "tEXt"
const data = new Uint8Array([...]) // chunk data

const crc = computeCRC32(type, data)

Notes

These utilities are exported for advanced use cases. Most applications won't need them directly:

• Base64: Used internally for PNG text chunk encoding. May be useful if you're handling raw card data strings.

• CRC-32: Used internally for PNG chunk validation. Useful if you're implementing custom PNG manipulation.

The library handles all encoding and checksum computation automatically when you use the high-level read/write functions.