base64-arraybuffer-es6/dist/base64-arraybuffer-es.js

Encode/decode base64 data into ArrayBuffers

/*
 * base64-arraybuffer
 * https://github.com/niklasvh/base64-arraybuffer
 *
 * Copyright (c) 2017-2023 Brett Zamir, 2012 Niklas von Hertzen
 * Licensed under the MIT license.
 */

/**
 * @typedef {number} Integer
 */

var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
  lookup[/** @type {number} */chars.codePointAt(i)] = i;
}

/**
 * @param {ArrayBuffer} arraybuffer
 * @param {Integer} [byteOffset]
 * @param {Integer} [lngth]
 * @returns {string}
 */
var encode = function encode(arraybuffer, byteOffset, lngth) {
  if (lngth === null || lngth === undefined) {
    lngth = arraybuffer.byteLength; // Needed for Safari
  }

  var bytes = new Uint8Array(arraybuffer, byteOffset || 0,
  // Default needed for Safari
  lngth);
  var len = bytes.length;
  var base64 = '';
  for (var _i = 0; _i < len; _i += 3) {
    base64 += chars[bytes[_i] >> 2];
    base64 += chars[(bytes[_i] & 3) << 4 | bytes[_i + 1] >> 4];
    base64 += chars[(bytes[_i + 1] & 15) << 2 | bytes[_i + 2] >> 6];
    base64 += chars[bytes[_i + 2] & 63];
  }
  if (len % 3 === 2) {
    base64 = base64.slice(0, -1) + '=';
  } else if (len % 3 === 1) {
    base64 = base64.slice(0, -2) + '==';
  }
  return base64;
};

/**
 * @param {string} base64
 * @param {{
 *   maxByteLength: number
 * }} [options]
 * @returns {ArrayBuffer}
 */
var decode = function decode(base64, options) {
  var len = base64.length;
  if (len % 4) {
    throw new Error('Bad base64 length: not divisible by four');
  }
  var bufferLength = base64.length * 0.75;
  var p = 0;
  var encoded1, encoded2, encoded3, encoded4;
  if (base64[base64.length - 1] === '=') {
    bufferLength--;
    if (base64[base64.length - 2] === '=') {
      bufferLength--;
    }
  }

  // @ts-expect-error Second argument is not yet standard
  var arraybuffer = new ArrayBuffer(bufferLength, options),
    bytes = new Uint8Array(arraybuffer);
  for (var _i2 = 0; _i2 < len; _i2 += 4) {
    // We know the result will not be undefined, as we have a text
    //   length divisible by four
    encoded1 = lookup[/** @type {number} */base64.codePointAt(_i2)];
    encoded2 = lookup[/** @type {number} */base64.codePointAt(_i2 + 1)];
    encoded3 = lookup[/** @type {number} */base64.codePointAt(_i2 + 2)];
    encoded4 = lookup[/** @type {number} */base64.codePointAt(_i2 + 3)];
    bytes[p++] = encoded1 << 2 | encoded2 >> 4;
    bytes[p++] = (encoded2 & 15) << 4 | encoded3 >> 2;
    bytes[p++] = (encoded3 & 3) << 6 | encoded4 & 63;
  }
  return arraybuffer;
};

export { decode, encode };