if (pageLen > fileHeader.getWorkSize()) pageLen = fileHeader.getWorkSize();
        public void rewind() throws IOException {            LOG.debug("Rewind: " + markedPage + ":" + markedOffset);            try {                lock.acquire(Lock.READ_LOCK);                nextPage = getSinglePage(markedPage);                pageLen = nextPage.ph.getDataLength();                offset = markedOffset;                dataCache.add(nextPage);            } catch (LockException e) {                throw new IOException("failed to acquire a read lock on "                        + getFile().getName());            } finally {                lock.release();            }        }