private String read(String chunk_uuid)  {
		// TODO Auto-generated method stub
		FileInputStream fis;
		try {
			fis = new FileInputStream(path+chunk_uuid);
			byte[] buf = new byte[fis.available()];// һոպõĻ
			fis.read(buf);
			fis.close();
			return new String(buf);
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			return "-1"; // ļڷΧ-1Ӷһȡ
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return "-1"; 
		}
	}