discordeno/packages/old/utils/src/base64.ts

/**
 * CREDIT: https://gist.github.com/enepomnyaschih/72c423f727d395eeaa09697058238727
 * Encodes a given Uint8Array, ArrayBuffer or string into RFC4648 base64 representation
 * @param data
 */
export function encode (data: ArrayBuffer | string): string {
  const uint8 = typeof data === 'string'
    ? new TextEncoder().encode(data)
    : data instanceof Uint8Array
      ? data
      : new Uint8Array(data)
  let result = ''
  let i
  const l = uint8.length
  for (i = 2; i < l; i += 3) {
    result += base64abc[uint8[i - 2] >> 2]
    result += base64abc[((uint8[i - 2] & 0x03) << 4) | (uint8[i - 1] >> 4)]
    result += base64abc[((uint8[i - 1] & 0x0f) << 2) | (uint8[i] >> 6)]
    result += base64abc[uint8[i] & 0x3f]
  }
  if (i === l + 1) {
    // 1 octet yet to write
    result += base64abc[uint8[i - 2] >> 2]
    result += base64abc[(uint8[i - 2] & 0x03) << 4]
    result += '=='
  }
  if (i === l) {
    // 2 octets yet to write
    result += base64abc[uint8[i - 2] >> 2]
    result += base64abc[((uint8[i - 2] & 0x03) << 4) | (uint8[i - 1] >> 4)]
    result += base64abc[(uint8[i - 1] & 0x0f) << 2]
    result += '='
  }
  return result
}

/**
 * CREDIT: https://gist.github.com/enepomnyaschih/72c423f727d395eeaa09697058238727
 * Decodes RFC4648 base64 string into an Uint8Array
 * @param data
 */
export function decode (data: string): Uint8Array {
  if (data.length % 4 !== 0) {
    throw new Error('Unable to parse base64 string.')
  }
  const index = data.indexOf('=')
  if (index !== -1 && index < data.length - 2) {
    throw new Error('Unable to parse base64 string.')
  }
  const missingOctets = data.endsWith('==') ? 2 : data.endsWith('=') ? 1 : 0
  const n = data.length
  const result = new Uint8Array(3 * (n / 4))
  let buffer
  for (let i = 0, j = 0; i < n; i += 4, j += 3) {
    buffer = getBase64Code(data.charCodeAt(i)) << 18 |
      getBase64Code(data.charCodeAt(i + 1)) << 12 |
      getBase64Code(data.charCodeAt(i + 2)) << 6 |
      getBase64Code(data.charCodeAt(i + 3))
    result[j] = buffer >> 16
    result[j + 1] = (buffer >> 8) & 0xFF
    result[j + 2] = buffer & 0xFF
  }
  return result.subarray(0, result.length - missingOctets)
}

/**
 * CREDIT: https://gist.github.com/enepomnyaschih/72c423f727d395eeaa09697058238727
 * @param charCode
 */
function getBase64Code (charCode: number): number {
  if (charCode >= base64codes.length) {
    throw new Error('Unable to parse base64 string.')
  }
  const code = base64codes[charCode]
  if (code === 255) {
    throw new Error('Unable to parse base64 string.')
  }
  return code
}

// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
const base64abc = [
  'A',
  'B',
  'C',
  'D',
  'E',
  'F',
  'G',
  'H',
  'I',
  'J',
  'K',
  'L',
  'M',
  'N',
  'O',
  'P',
  'Q',
  'R',
  'S',
  'T',
  'U',
  'V',
  'W',
  'X',
  'Y',
  'Z',
  'a',
  'b',
  'c',
  'd',
  'e',
  'f',
  'g',
  'h',
  'i',
  'j',
  'k',
  'l',
  'm',
  'n',
  'o',
  'p',
  'q',
  'r',
  's',
  't',
  'u',
  'v',
  'w',
  'x',
  'y',
  'z',
  '0',
  '1',
  '2',
  '3',
  '4',
  '5',
  '6',
  '7',
  '8',
  '9',
  '+',
  '/'
]

// CREDIT: https://gist.github.com/enepomnyaschih/72c423f727d395eeaa09697058238727
const base64codes = [
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  255,
  62,
  255,
  255,
  255,
  63,
  52,
  53,
  54,
  55,
  56,
  57,
  58,
  59,
  60,
  61,
  255,
  255,
  255,
  0,
  255,
  255,
  255,
  0,
  1,
  2,
  3,
  4,
  5,
  6,
  7,
  8,
  9,
  10,
  11,
  12,
  13,
  14,
  15,
  16,
  17,
  18,
  19,
  20,
  21,
  22,
  23,
  24,
  25,
  255,
  255,
  255,
  255,
  255,
  255,
  26,
  27,
  28,
  29,
  30,
  31,
  32,
  33,
  34,
  35,
  36,
  37,
  38,
  39,
  40,
  41,
  42,
  43,
  44,
  45,
  46,
  47,
  48,
  49,
  50,
  51
]