code: public static AsciiString readAsciiString(DataInput in) throws IOException {
          short len=in.readShort();
          if(len < 0)
              return null;
          AsciiString retval=new AsciiString(len);
          in.readFully(retval.chars());
          return retval;
      }
docs: Reads an AsciiString from buf. The length is read first, followed by the chars. Each char is a single byte
  @param in the input stream
  @return the string read from buf