patch-FileReader.js

/**
 * @format
 */
FileReader.prototype.readAsArrayBuffer = function(blob) {
  if (this.readyState === this.LOADING) throw new Error('InvalidStateError');
  this._setReadyState(this.LOADING);
  this._result = null;
  this._error = null;
  const fr = new FileReader();
  fr.onloadend = () => {
    const content = atob(fr.result.replace(/data:[^;]+;base64,/, ""));
    const buffer = new ArrayBuffer(content.length);
    const view = new Uint8Array(buffer);
    view.set(Array.from(content).map(c => c.charCodeAt(0)));
    this._result = buffer;
    this._setReadyState(this.DONE);
  };
  fr.readAsDataURL(blob);
};

// from: https://stackoverflow.com/questions/42829838/react-native-atob-btoa-not-working-without-remote-js-debugging
const chars =
  'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
const atob = (input = '') => {
  let str = input.replace(/=+$/, '');
  let output = '';

  if (str.length % 4 == 1) {
    throw new Error(
      "'atob' failed: The string to be decoded is not correctly encoded.",
    );
  }
  for (
    let bc = 0, bs = 0, buffer, i = 0;
    (buffer = str.charAt(i++));
    ~buffer && ((bs = bc % 4 ? bs * 64 + buffer : buffer), bc++ % 4)
      ? (output += String.fromCharCode(255 & (bs >> ((-2 * bc) & 6))))
      : 0
  ) {
    buffer = chars.indexOf(buffer);
  }

  return output;
};