Base64.as

/* Base64 library for ActionScript 3.0.
* Based on: Ma Bingyao code.
* Optimized by: Jean-Philippe Auclair  / jpauclair.wordpress.com
* Copyright (C) 2007 Ma Bingyao <andot@ujn.edu.cn>
* LastModified: Oct 26, 2009
* This library is free.  You can redistribute it and/or modify it.
*/
package
{
    import flash.utils.ByteArray;
    public class Base64
	{
        private static const _encodeChars:Vector.<int> = InitEncoreChar();
        private static const _decodeChars:Vector.<int> = InitDecodeChar();

        public static function encode(data:ByteArray):String
		{
			var out:ByteArray = new ByteArray();
			//Presetting the length keep the memory smaller and optimize speed since there is no "grow" needed
			out.length = (2 + data.length - ((data.length + 2) % 3)) * 4 / 3; //Preset length //1.6 to 1.5 ms
			var i:int = 0;
            var r:int = data.length % 3;
            var len:int = data.length - r;
            var c:int;   //read (3) character AND write (4) characters

            while (i < len)
			{
				//Read 3 Characters (8bit * 3 = 24 bits)
                c = data[i++] << 16 | data[i++] << 8 | data[i++];   

				//Cannot optimize this to read int because of the positioning overhead. (as3 bytearray seek is slow)
				//Convert to 4 Characters (6 bit * 4 = 24 bits)
				c = (_encodeChars[c >>> 18] << 24) | (_encodeChars[c >>> 12 & 0x3f] << 16) | (_encodeChars[c >>> 6 & 0x3f] << 8 ) | _encodeChars[c & 0x3f];

				//Optimization: On older and slower computer, do one write Int instead of 4 write byte: 1.5 to 0.71 ms
				out.writeInt(c);
				/*
				out.writeByte(_encodeChars[c >> 18] );
				out.writeByte(_encodeChars[c >> 12 & 0x3f]);
				out.writeByte(_encodeChars[c >> 6 & 0x3f]);
				out.writeByte(_encodeChars[c & 0x3f]);
				*/
            }   

            if (r == 1) //Need two "=" padding
			{
				//Read one char, write two chars, write padding
                c = data[i];
				c = (_encodeChars[c >>> 2] << 24) | (_encodeChars[(c & 0x03) << 4] << 16) | 61 << 8 | 61;
				out.writeInt(c);
            }
            else if (r == 2) //Need one "=" padding
			{
                c = data[i++] << 8 | data[i];
				c = (_encodeChars[c >>> 10] << 24) | (_encodeChars[c >>> 4 & 0x3f] << 16) | (_encodeChars[(c & 0x0f) << 2] << 8 ) | 61;
				out.writeInt(c);
            }   

            out.position = 0;
			return out.readUTFBytes(out.length);
        }   

        public static function decode(str:String):ByteArray
		{
            var c1:int;
            var c2:int;
            var c3:int;
            var c4:int;
            var i:int;
            var len:int;
            var out:ByteArray;
            len = str.length;
            i = 0;
            out = new ByteArray();
            var byteString:ByteArray = new ByteArray();
			byteString.writeUTFBytes(str);
            while (i < len)
			{
				//c1
                do
				{
                    c1 = _decodeChars[byteString[i++]];
                } while (i < len && c1 == -1);
                if (c1 == -1) break;   

				//c2
                do
				{
                    c2 = _decodeChars[byteString[i++]];
                } while (i < len && c2 == -1);
                if (c2 == -1) break;    

                out.writeByte((c1 << 2) | ((c2 & 0x30) >> 4));   

				//c3
                do
                {
                    c3 = byteString[i++];
                    if (c3 == 61) return out;   

                    c3 = _decodeChars[c3];
                } while (i < len && c3 == -1);
                if (c3 == -1) break;   

                out.writeByte(((c2 & 0x0f) << 4) | ((c3 & 0x3c) >> 2));   

				//c4
                do {
                    c4 = byteString[i++];
                    if (c4 == 61) return out;

                    c4 = _decodeChars[c4];
                } while (i < len && c4 == -1);
                if (c4 == -1) break;   

                out.writeByte(((c3 & 0x03) << 6) | c4);   

            }
            return out;
        }   

		public static function InitEncoreChar() : Vector.<int>
		{
			var encodeChars:Vector.<int> = new Vector.<int>();

			// We could push the number directly, but i think it's nice to see the characters (with no overhead on encode/decode)
			var chars:String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
			for (var i:int = 0; i < 64; i++)
			{
				encodeChars.push(chars.charCodeAt(i));
			}
			/*
				encodeChars.push(
				65, 66, 67, 68, 69, 70, 71, 72,
				73, 74, 75, 76, 77, 78, 79, 80,
				81, 82, 83, 84, 85, 86, 87, 88,
				89, 90, 97, 98, 99, 100, 101, 102,
				103, 104, 105, 106, 107, 108, 109, 110,
				111, 112, 113, 114, 115, 116, 117, 118,
				119, 120, 121, 122, 48, 49, 50, 51,
				52, 53, 54, 55, 56, 57, 43, 47);
			*/
			return encodeChars;
		}

		public static function InitDecodeChar() : Vector.<int>
		{
			var decodeChars:Vector.<int> = new Vector.<int>();

			decodeChars.push(-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
							 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
							 -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
							 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
							 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
							 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
							 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1);
			return decodeChars;
		}
    }
}