将Arraybuffer编码为Base32

Question

我正在尝试将ArrayBuffer javascript对象编码为base32 String，但没有成功。 有没有人对我如何做到这一点有任何建议？这是我现在拥有的。 我已经修改了base32-js项目中的一些代码。

var alphabet = '0123456789abcdefghjkmnpqrtuvwxyz'
var alias = { o:0, i:1, l:1, s:5 }
var lookup = function() {
    var table = {}
    for (var i = 0; i < alphabet.length; i++) {
        table[alphabet[i]] = i
    }
    for (var key in alias) {
        if (!alias.hasOwnProperty(key)) continue
        table[key] = table['' + alias[key]]
    }
    lookup = function() { return table }
    return table
}
function Encoder() {
    var skip = 0
    var bits = 0
    this.output = ''
    this.readByte = function(byte) {
        if (typeof byte == 'string') byte = byte.charCodeAt(0)
        if (skip < 0) {
            bits |= (byte >> (-skip))
        } else {
            bits = (byte << skip) & 248
        }
        if (skip > 3) {
            skip -= 8
            return 1
        }
        if (skip < 4) {
            this.output += alphabet[bits >> 3]
            skip += 5
        }
        return 0
    }
    this.finish = function(check) {
        var output = this.output + (skip < 0 ? alphabet[bits >> 3] : '') + (check ? '$' : '')
        this.output = ''
        return output
    }
}
Encoder.prototype.update = function(input, flush) {
    for (var i = 0; i < input.length; ) {
        i += this.readByte(input[i])
    }
    // consume all output
    var output = this.output
    this.output = ''
    if (flush) {
      output += this.finish()
    }
    return output
}
function encode(input) {
  var encoder = new Encoder()
  var output = encoder.update(input, true)
  return output
}
var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://www.richerlife.com/wp-content/uploads/2012/01/google-logo-682-571408a.jpg', false);
xhr.overrideMimeType("text/plain; charset=x-user-defined");  
xhr.onload = function(e) {
  if (this.status == 200) {
    alert(encode(xhr.responseText));
  }
};
xhr.send();