protected void read(long offset,byte[] b) throws IOException {
  rafile.seek(offset);
  if (rafile.read(b) != b.length) {
    throw new IOException("Not enough bytes available in file " + getPath());
  }
}

protected void read ( long offset , byte [ ] b ) throws IOException { rafile . seek ( offset ) ; if ( rafile . read ( b ) != b . length ) { throw new IOException ( "Not enough bytes available in file " + getPath ( ) ) ; } }
reads a number of bytes from the rrd file on the disk
