'use strict';

module.exports = function base64_decode(encodedData) {
  // eslint-disable-line camelcase
  //  discuss at: https://locutus.io/php/base64_decode/
  // original by: Tyler Akins (https://rumkin.com)
  // improved by: Thunder.m
  // improved by: Kevin van Zonneveld (https://kvz.io)
  // improved by: Kevin van Zonneveld (https://kvz.io)
  //    input by: Aman Gupta
  //    input by: Brett Zamir (https://brett-zamir.me)
  // bugfixed by: Onno Marsman (https://twitter.com/onnomarsman)
  // bugfixed by: Pellentesque Malesuada
  // bugfixed by: Kevin van Zonneveld (https://kvz.io)
  // improved by: Indigo744
  //   example 1: base64_decode('S2V2aW4gdmFuIFpvbm5ldmVsZA==')
  //   returns 1: 'Kevin van Zonneveld'
  //   example 2: base64_decode('YQ==')
  //   returns 2: 'a'
  //   example 3: base64_decode('4pyTIMOgIGxhIG1vZGU=')
  //   returns 3: '✓ à la mode'

  // decodeUTF8string()
  // Internal function to decode properly UTF8 string
  // Adapted from Solution #1 at https://developer.mozilla.org/en-US/docs/Web/API/WindowBase64/Base64_encoding_and_decoding
  var decodeUTF8string = function decodeUTF8string(str) {
    // Going backwards: from bytestream, to percent-encoding, to original string.
    return decodeURIComponent(str.split('').map(function (c) {
      return '%' + ('00' + c.charCodeAt(0).toString(16)).slice(-2);
    }).join(''));
  };

  if (typeof window !== 'undefined') {
    if (typeof window.atob !== 'undefined') {
      return decodeUTF8string(window.atob(encodedData));
    }
  } else {
    return new Buffer(encodedData, 'base64').toString('utf-8');
  }

  var b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
  var o1 = void 0;
  var o2 = void 0;
  var o3 = void 0;
  var h1 = void 0;
  var h2 = void 0;
  var h3 = void 0;
  var h4 = void 0;
  var bits = void 0;
  var i = 0;
  var ac = 0;
  var dec = '';
  var tmpArr = [];

  if (!encodedData) {
    return encodedData;
  }

  encodedData += '';

  do {
    // unpack four hexets into three octets using index points in b64
    h1 = b64.indexOf(encodedData.charAt(i++));
    h2 = b64.indexOf(encodedData.charAt(i++));
    h3 = b64.indexOf(encodedData.charAt(i++));
    h4 = b64.indexOf(encodedData.charAt(i++));

    bits = h1 << 18 | h2 << 12 | h3 << 6 | h4;

    o1 = bits >> 16 & 0xff;
    o2 = bits >> 8 & 0xff;
    o3 = bits & 0xff;

    if (h3 === 64) {
      tmpArr[ac++] = String.fromCharCode(o1);
    } else if (h4 === 64) {
      tmpArr[ac++] = String.fromCharCode(o1, o2);
    } else {
      tmpArr[ac++] = String.fromCharCode(o1, o2, o3);
    }
  } while (i < encodedData.length);

  dec = tmpArr.join('');

  return decodeUTF8string(dec.replace(/\0+$/, ''));
};
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