public static byte[] unEscape(byte[] oData){
		byte[] nData = new byte[oData.length];
		int i = 0;
		byte b;
		byte next;
		for(int j = 0;j < oData.length;j ++){
			b = oData[j];
			if(4 == b){
				if(j  == oData.length - 1){
					continue;
				}
				next = oData[j + 1];
				if(4 == next){
					nData[i] = oData[j];
					j ++;
				}else if(5 == next){
					nData[i] = 2;
					j ++;
				}else if(6 == next){
					nData[i] = 3;
					j ++;
				}else{
					nData[i] = oData[j];
				}
			}else {
				nData[i] = oData[j];
			}
			i ++;
		}
		byte[] ret = new byte[i];
		System.arraycopy(nData, 0, ret, 0, ret.length);
		//debug
		//System.out.println("unEscapebyte:" + dump(ret));
		return ret;
	}