base64.js

// I did not write this file. For copyright info, please refer to LICENSE.

function StringBuffer()
{
    this.buffer = [];
}

StringBuffer.prototype.append = function append(string)
{
    this.buffer.push(string);
    return this;
};

StringBuffer.prototype.toString = function toString()
{
    return this.buffer.join("");
};

var Base64 =
{
    codex : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

    encode : function (input)
    {
        var output = new StringBuffer();

        var enumerator = new Utf8EncodeEnumerator(input);
        while (enumerator.moveNext())
        {
            var chr1 = enumerator.current;

            enumerator.moveNext();
            var chr2 = enumerator.current;

            enumerator.moveNext();
            var chr3 = enumerator.current;

            var enc1 = chr1 >> 2;
            var enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            var enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            var enc4 = chr3 & 63;

            if (isNaN(chr2))
            {
                enc3 = enc4 = 64;
            }
            else if (isNaN(chr3))
            {
                enc4 = 64;
            }

            output.append(this.codex.charAt(enc1) + this.codex.charAt(enc2) + this.codex.charAt(enc3) + this.codex.charAt(enc4));
        }

        return output.toString();
    },

    decode : function (input)
    {
        var output = new StringBuffer();

        var enumerator = new Base64DecodeEnumerator(input);
        while (enumerator.moveNext())
        {
            var charCode = enumerator.current;

            if (charCode < 128)
                output.append(String.fromCharCode(charCode));
            else if ((charCode > 191) && (charCode < 224))
            {
                enumerator.moveNext();
                var charCode2 = enumerator.current;

                output.append(String.fromCharCode(((charCode & 31) << 6) | (charCode2 & 63)));
            }
            else
            {
                enumerator.moveNext();
                var charCode2 = enumerator.current;

                enumerator.moveNext();
                var charCode3 = enumerator.current;

                output.append(String.fromCharCode(((charCode & 15) << 12) | ((charCode2 & 63) << 6) | (charCode3 & 63)));
            }
        }

        return output.toString();
    }
}


function Utf8EncodeEnumerator(input)
{
    this._input = input;
    this._index = -1;
    this._buffer = [];
}

Utf8EncodeEnumerator.prototype =
{
    current: Number.NaN,

    moveNext: function()
    {
        if (this._buffer.length > 0)
        {
            this.current = this._buffer.shift();
            return true;
        }
        else if (this._index >= (this._input.length - 1))
        {
            this.current = Number.NaN;
            return false;
        }
        else
        {
            var charCode = this._input.charCodeAt(++this._index);

            // "\r\n" -> "\n"
            //
            if ((charCode == 13) && (this._input.charCodeAt(this._index + 1) == 10))
            {
                charCode = 10;
                this._index += 2;
            }

            if (charCode < 128)
            {
                this.current = charCode;
            }
            else if ((charCode > 127) && (charCode < 2048))
            {
                this.current = (charCode >> 6) | 192;
                this._buffer.push((charCode & 63) | 128);
            }
            else
            {
                this.current = (charCode >> 12) | 224;
                this._buffer.push(((charCode >> 6) & 63) | 128);
                this._buffer.push((charCode & 63) | 128);
            }

            return true;
        }
    }
}

function Base64DecodeEnumerator(input)
{
    this._input = input;
    this._index = -1;
    this._buffer = [];
}

Base64DecodeEnumerator.prototype =
{
    current: 64,

    moveNext: function()
    {
        if (this._buffer.length > 0)
        {
            this.current = this._buffer.shift();
            return true;
        }
        else if (this._index >= (this._input.length - 1))
        {
            this.current = 64;
            return false;
        }
        else
        {
            var enc1 = Base64.codex.indexOf(this._input.charAt(++this._index));
            var enc2 = Base64.codex.indexOf(this._input.charAt(++this._index));
            var enc3 = Base64.codex.indexOf(this._input.charAt(++this._index));
            var enc4 = Base64.codex.indexOf(this._input.charAt(++this._index));

            var chr1 = (enc1 << 2) | (enc2 >> 4);
            var chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            var chr3 = ((enc3 & 3) << 6) | enc4;

            this.current = chr1;

            if (enc3 != 64)
                this._buffer.push(chr2);

            if (enc4 != 64)
                this._buffer.push(chr3);

            return true;
        }
    }
};