/**
 * OFBMode
 * 
 * An ActionScript 3 implementation of the OFB confidentiality mode
 * Copyright (c) 2007 Henri Torgemane
 * 
 * See LICENSE.txt for full license information.
 */
package com.hurlant.crypto.symmetric
{
    import flash.utils.ByteArray;

    public class OFBMode extends IVMode implements IMode
    {
        public function OFBMode(key:ISymmetricKey, padding:IPad=null)
        {
            super(key, null);
        }
        
        public function encrypt(src:ByteArray):void
        {
            var vector:ByteArray = getIV4e();
            core(src, vector);
        }
        
        public function decrypt(src:ByteArray):void
        {
            var vector:ByteArray = getIV4d();
            core(src, vector);
        }
        
        private function core(src:ByteArray, iv:ByteArray):void { 
            var l:uint = src.length;
            var tmp:ByteArray = new ByteArray;
            for (var i:uint=0;i<src.length;i+=blockSize) {
                key.encrypt(iv);
                tmp.position=0;
                tmp.writeBytes(iv);
                var chunk:uint = (i+blockSize<l)?blockSize:l-i;
                for (var j:uint=0;j<chunk;j++) {
                    src[i+j] ^= iv[j];
                }
                iv.position=0;
                iv.writeBytes(tmp);
            }
        }
        public function toString():String {
            return key.toString()+"-ofb";
        }
        
    }
}