@thatgameco/base32/index.js

Simple base32 encoder / decoder

const RFC4648 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
const RFC4648_HEX = '0123456789ABCDEFGHIJKLMNOPQRSTUV'
const CROCKFORD = '0123456789ABCDEFGHJKMNPQRSTVWXYZ'

const toDataView = (data) => {
  if (typeof data === 'string') {
    data = Buffer.from(data)
  }
  if (data instanceof Int8Array || data instanceof Uint8Array || data instanceof Uint8ClampedArray) {
    return new DataView(data.buffer, data.byteOffset, data.byteLength)
  }
  if (data instanceof ArrayBuffer) {
    return new DataView(data)
  }
  throw new TypeError('Expected `data` to be a string, ArrayBuffer, Buffer, Int8Array, Uint8Array or Uint8ClampedArray')
}

const readChar = (charset, char) => {
  const idx = charset.indexOf(char)
  if (idx === -1) {
    throw new Error('Invalid character found: ' + char)
  }
  return idx
}

const Base32 = (options = {}) => {
  let { type = 'RFC4648', charset, padding } = options
  if (charset == null) {
    switch (type) {
      case 'RFC3548':
      case 'RFC4648':
        charset = RFC4648
        padding = padding != null ? padding : '='
        break
      case 'RFC4648-HEX':
        charset = RFC4648_HEX
        padding = padding != null ? padding : '='
        break
      case 'Crockford':
        charset = CROCKFORD
        break
      default:
        throw new Error(`Unknown base32 encoding type: ${type}`)
    }
  }

  const encode = (input) => {
    const view = toDataView(input)
    let bits = 0
    let value = 0
    let output = ''

    for (let i = 0; i < view.byteLength; i++) {
      value = (value << 8) | view.getUint8(i)
      bits += 8
      while (bits >= 5) {
        output += charset[(value >>> (bits - 5)) & 31]
        bits -= 5
      }
    }
    if (bits > 0) {
      output += charset[(value << (5 - bits)) & 31]
    }

    if (padding) {
      while ((output.length % 8) !== 0) {
        output += padding
      }
    }
    return output
  }

  const decode = (input, encoding = 'utf-8') => {
    if (type === 'Crockford') {
      input = input.toUpperCase().replace(/O/g, '0').replace(/[IL]/g, '1')
    } else if (padding) {
      input = input.replace(new RegExp(`${padding}+$`), '')
    }
    const length = input.length
    let bits = 0
    let value = 0

    let index = 0
    const output = new Uint8Array((length * 5 / 8) | 0)

    for (let i = 0; i < length; i++) {
      value = (value << 5) | readChar(charset, input[i])
      bits += 5

      if (bits >= 8) {
        output[index++] = (value >>> (bits - 8)) & 255
        bits -= 8
      }
    }
    return encoding ? Buffer.from(output.buffer).toString(encoding) : output.buffer
  }

  return { encode, decode }
}

module.exports = Base32