public Long getBytes() {
      return bytes;
    }
Size of the stream as a byte-count, or zero if yet unknown.

<p>See also {@link org.datatransferproject.transfer.CallableSizeCalculator} and {@
com.google.common.io.CountingInputStream} for some brute-force options when the return is
zero.
portability-spi-cloud/src/main/java/org/datatransferproject/spi/cloud/storage/TemporaryPerJobDataStore.java