Example #1
0
    /**
     * Returns the next object from the log, or null if none available.
     *
     * @return The log record, or null if EOF
     * @throws IOException If there is a low-level I/O error.
     */
    public Object next() throws IOException {
      if (prevPos <= 0) return null;

      long endOfThisRecord = prevPos;

      int thisLength = nextLength;

      long recordStart = prevPos - thisLength; // back up to the beginning of the next record
      prevPos = recordStart - 4; // back up 4 more to read the length of the next record

      if (prevPos <= 0) return null; // this record is the header

      long bufferPos = fis.getBufferPos();
      if (prevPos >= bufferPos) {
        // nothing to do... we're within the current buffer
      } else {
        // Position buffer so that this record is at the end.
        // For small records, this will cause subsequent calls to next() to be within the buffer.
        long seekPos = endOfThisRecord - fis.getBufferSize();
        seekPos =
            Math.min(
                seekPos,
                prevPos); // seek to the start of the record if it's larger then the block size.
        seekPos = Math.max(seekPos, 0);
        fis.seek(seekPos);
        fis.peek(); // cause buffer to be filled
      }

      fis.seek(prevPos);
      nextLength =
          fis.readInt(); // this is the length of the *next* record (i.e. closer to the beginning)

      // TODO: optionally skip document data
      Object o = codec.readVal(fis);

      // assert fis.position() == prevPos + 4 + thisLength;  // this is only true if we read all the
      // data (and we currently skip reading SolrInputDocument

      return o;
    }
Example #2
0
    public FSReverseReader() throws IOException {
      incref();

      long sz;
      synchronized (TransactionLog.this) {
        fos.flushBuffer();
        sz = fos.size();
        assert sz == channel.size();
      }

      fis = new ChannelFastInputStream(channel, 0);
      if (sz >= 4) {
        // readHeader(fis);  // should not be needed
        prevPos = sz - 4;
        fis.seek(prevPos);
        nextLength = fis.readInt();
      }
    }