typescript——BASE64

/**
 *
 * @author 
 *
 */
class Base64Util {
    public constructor() {
    }

    public static BASE64_CHARS:string = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

        public static version:string = "1.0.0";

        public static encode(data:string):string {
            // Convert string to ByteArray
            var bytes: egret.ByteArray = new egret.ByteArray();
            bytes.writeUTFBytes(data);

            // Return encoded ByteArray
            return this.encodeByteArray(bytes);
        }

        private static encodeByteArray(data:egret.ByteArray):string {
            // Initialise output
            var output:string = "";

            // Create data and output buffers
            var dataBuffer:Array<any>;
            var outputBuffer:Array<any> = new Array(4);

            // Rewind ByteArray
            data.position = 0;

            // while there are still bytes to be processed
            while (data.bytesAvailable > 0) {
                // Create new data buffer and populate next 3 bytes from data
                dataBuffer = new Array();
                for (var i:number = 0; i < 3 && data.bytesAvailable > 0; i++) {
                    dataBuffer[i] = data.readUnsignedByte();
                }

                // Convert to data buffer Base64 character positions and 
                // store in output buffer
                outputBuffer[0] = (dataBuffer[0] & 0xfc) >> 2;
                outputBuffer[1] = ((dataBuffer[0] & 0x03) << 4) | ((dataBuffer[1]) >> 4);
                outputBuffer[2] = ((dataBuffer[1] & 0x0f) << 2) | ((dataBuffer[2]) >> 6);
                outputBuffer[3] = dataBuffer[2] & 0x3f;

                // If data buffer was short (i.e not 3 characters) then set
                // end character indexes in data buffer to index of '=' symbol.
                // This is necessary because Base64 data is always a multiple of
                // 4 bytes and is basses with '=' symbols.
                for (var j:number = dataBuffer.length; j < 3; j++) {
                    outputBuffer[j + 1] = 64;
                }

                // Loop through output buffer and add Base64 characters to 
                // encoded data string for each character.
                for (var k:number = 0; k < outputBuffer.length; k++) {
                    output += this.BASE64_CHARS.charAt(outputBuffer[k]);
                }
            }

            // Return encoded data
            return output;
        }

        public static decode(data:string):string {
            // Decode data to ByteArray
            var bytes:egret.ByteArray = this.decodeToByteArray(data);

            // Convert to string and return
            return bytes.readUTFBytes(bytes.length);
        }

        private static decodeToByteArray(data:String):egret.ByteArray {
            // Initialise output ByteArray for decoded data
            var output:egret.ByteArray = new egret.ByteArray();

            // Create data and output buffers
            var dataBuffer:Array<any> = new Array(4);
            var outputBuffer: Array<any> = new Array(3);

            // While there are data bytes left to be processed
            for (var i:number = 0; i < data.length; i += 4) {
                // Populate data buffer with position of Base64 characters for
                // next 4 bytes from encoded data
                for(var j: number = 0; j < 4 && i + j < data.length; j++) {
                    dataBuffer[j] = this.BASE64_CHARS.indexOf(data.charAt(i + j));
                }

                // Decode data buffer back into bytes
                outputBuffer[0] = (dataBuffer[0] << 2) + ((dataBuffer[1] & 0x30) >> 4);
                outputBuffer[1] = ((dataBuffer[1] & 0x0f) << 4) + ((dataBuffer[2] & 0x3c) >> 2);        
                outputBuffer[2] = ((dataBuffer[2] & 0x03) << 6) + dataBuffer[3];

                // Add all non-padded bytes in output buffer to decoded data
                for(var k: number = 0; k < outputBuffer.length; k++) {
                    if (dataBuffer[k+1] == 64) break;
                    output.writeByte(outputBuffer[k]);
                }
            }

            // Rewind decoded data ByteArray
            output.position = 0;

            // Return decoded data
            return output;
        }
}