Flatbuffers

sample.java

private int[] addEventsToBuffer(FlatBufferBuilder fbb, List<Map<String, Object>> events)
      throws Exception {
    Checksum checksum = new CRC32();

    int[] eventOffsets = new int[events.size()];
    int idx = 0;
    for (Map<String, Object> event : events) {
      // Create body
      Map<String, Object> bodyMap = clean(event);
      byte[] body = bodySerializer.serialize(bodyMap);
      int bodyOffset = Event.createBodyVector(fbb, body);

      // Start event so creation isn't nested
      // https://github.com/google/flatbuffers/issues/19
      Event.startEvent(fbb);

      // Headers
      Event.addHeader1(fbb, createHeader1(fbb, event, (short) body.length));
      Event.addHeader2(fbb, createHeader2(fbb, event));
      Event.addHeader3(fbb, createHeader3(fbb, event));
      Event.addHeader4(fbb, createHeader4(fbb, event));

      // it's written in reverse order, so the start is the current offset.
      int headerStart = fbb.offset();
      // end is at bodyOffset
      int headerLength = headerStart - (bodyOffset - 1);
      int end = headerStart + headerLength;
      int cap = fbb.dataBuffer().capacity();

      // ensure we don't read beyond the capacity of the databuffer
      if (end > cap) {
        headerLength -= (end - cap);
      }
      byte[] headerBytes = fbb.sizedByteArray(headerStart, headerLength);
      checksum.update(headerBytes, 0, headerBytes.length);
      Event.addHeaderChecksum(fbb, checksum.getValue());

      // Body
      checksum.reset();
      checksum.update(body, 0, body.length);
      Event.addBody(fbb, bodyOffset);
      Event.addBodyChecksum(fbb, checksum.getValue());

      eventOffsets[idx++] = Event.endEvent(fbb);
    }

    return eventOffsets;
  }