javascript base64 encode/decode

gistfile1.js

<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
 
<script type="text/javascript">

var nativeAtob = window.atob;
var nativeBtoa = window.btoa;

// http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#atob
(function (global) {
  "use strict";

  var a64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

  var a256 = "";
  var r64 = [];
  var i = -1;
  while (++i < 256) {
    a256 += String.fromCharCode(i);
  }
  var counter = 63;
  i = -1;
  while (counter >= 0) {
    var c = String.fromCharCode(++i);
    r64[i] = a64.indexOf(c);
    if (r64[i] !== -1) {
      --counter;
    }
  }

  function code(s, discard, alpha, beta, w1, w2) {
    var buffer = 0;
    var i = -1;
    var length = s.length;
    var result = '';
    var bitsInBuffer = 0;
    while (++i < length) {
      var c = s.charCodeAt(i);
      c = (alpha === null ? (c < 256 ? c : -1) : (c < alpha.length ? alpha[c] : -1));
      if (c === -1) {
        throw new RangeError();
      }
      buffer = (buffer << w1) + c;
      bitsInBuffer += w1;
      while (bitsInBuffer >= w2) {
        bitsInBuffer -= w2;
        var tmp = buffer >> bitsInBuffer;
        result += beta.charAt(tmp);
        buffer ^= tmp << bitsInBuffer;
      }
    }
    if (!discard && bitsInBuffer > 0) {
      result += beta.charAt(buffer << (w2 - bitsInBuffer));
    }
    return result;
  }

  global.btoa = function (s) {
    s = String(s);
    s = code(s, false, null, a64, 8, 6);
    return s + "====".slice((s.length % 4) || 4);
  };

  global.atob = function (s) {
    s = String(s);
    var length = s.length;
    var k = -1;
    var result = "";
    var i = 0;
    while (++k < length + 1) {
      if (k === length || s.charAt(k) === "=") {
        var p = s.slice(i, k);
        i = k + 1;
        if (p.length % 4 === 1) {
          throw new RangeError();
        }
        result += code(p, true, r64, a256, 6, 8);
      }
    }
    return result;
  };

}(this));

var decodeTests = [
  ['YW55IGNhcm5hbCBwbGVhc3VyZS4=', 'any carnal pleasure.'],
  ['YW55IGNhcm5hbCBwbGVhc3VyZQ==', 'any carnal pleasure'],
  ['YW55IGNhcm5hbCBwbGVhc3Vy', 'any carnal pleasur'],
  [Array(1e4).join('YW55IGNhcm5hbCBwbGVhc3Vy'), Array(1e4).join('any carnal pleasur')], // ~24 kb input
  ['YW55IGNhcm5hbCBwbGVhc3U=', 'any carnal pleasu'],
  ['YW55IGNhcm5hbCBwbGVhcw==', 'any carnal pleas'],
  ['YW55IGNhcm5hbCBwbGVhcw', 'any carnal pleas'],
  ['\uaaaa', null],
  ['YQ', 'a'],
  ['YR', 'a'],
  ['', ''],
  ['YQA=', 'a\u0000'],
  ['YW55IGNhcm5hbCBwbGVhcw==YW55IGNhcm5hbCBwbGVhc3VyZS4=', 'any carnal pleasany carnal pleasure.'],
  ['YW55IGNhcm5hbCBwbGVhcw==YW55IGNhcm5hbCBwbGVhc3VyZS4', 'any carnal pleasany carnal pleasure.']
];

var encodeTests = [
  ['', ''],
  ['\x00', 'AA=='],
  ['\xff\xff', '//8='],
  ['any carnal pleasure.', 'YW55IGNhcm5hbCBwbGVhc3VyZS4='],
  ['any carnal pleasure', 'YW55IGNhcm5hbCBwbGVhc3VyZQ=='],
  ['any carnal pleasur', 'YW55IGNhcm5hbCBwbGVhc3Vy'],
  [Array(1e4).join('any carnal pleasur'), Array(1e4).join('YW55IGNhcm5hbCBwbGVhc3Vy')], // ~24 kb output
  ['any carnal pleasu', 'YW55IGNhcm5hbCBwbGVhc3U='],
  ['any carnal pleas', 'YW55IGNhcm5hbCBwbGVhcw=='],
  ['a', 'YQ=='],
  ['', ''],
  ['\uaaaa', null],
  ['a\u0000', 'YQA=']
];

if (!window.console) {
  window.console = {
    log: function (x) {
      document.body.appendChild(document.createTextNode(x));
      document.body.appendChild(document.createElement('br'));
    }
  };
}
 
function runTests(tests, func, name) {
  var i, r, t = +new Date();
  for (i = 0; i < tests.length; i++) {
    try {
      r = func(tests[i][0]);
    } catch (e) {
      r = null;
    }
    if (r !== tests[i][1]) {
      console.log(i + ': ' + name + '(' + tests[i][0] + ') === ' + r + '(expected: ' + tests[i][1] + ')');
    }
  }
  t = +new Date() - t;
  console.log(name + ' - ' + t + 'ms');
}

setTimeout(function () {
  if (window.atob) {
    runTests(decodeTests, nativeAtob, 'window.atob - native');
  }
  runTests(decodeTests, window.atob, 'window.atob');
  if (window.btoa) {
    runTests(encodeTests, nativeBtoa, 'window.btoa - native');
  }
  runTests(encodeTests, window.btoa, 'window.btoa');
 
  console.log('finished');
}, 1);

</script>