src/base64Utils.js

/**
 * @license
 * Copyright 2017 The Emscripten Authors
 * SPDX-License-Identifier: MIT
 */

#if POLYFILL && (ENVIRONMENT_MAY_BE_SHELL || (ENVIRONMENT_MAY_BE_NODE && MIN_NODE_VERSION < 160000))
#include "polyfill/atob.js"
#endif

// Converts a string of base64 into a byte array (Uint8Array).
function intArrayFromBase64(s) {
#if ENVIRONMENT_MAY_BE_NODE
  if (typeof ENVIRONMENT_IS_NODE != 'undefined' && ENVIRONMENT_IS_NODE) {
    var buf = Buffer.from(s, 'base64');
    return new Uint8Array(buf.buffer, buf.byteOffset, buf.length);
  }
#endif

  var decoded = atob(s);
  var bytes = new Uint8Array(decoded.length);
  for (var i = 0 ; i < decoded.length ; ++i) {
    bytes[i] = decoded.charCodeAt(i);
  }
  return bytes;
}

// If filename is a base64 data URI, parses and returns data (Buffer on node,
// Uint8Array otherwise). If filename is not a base64 data URI, returns undefined.
function tryParseAsDataURI(filename) {
  if (!isDataURI(filename)) {
    return;
  }

  return intArrayFromBase64(filename.slice(dataURIPrefix.length));
}