Fetch the first n bytes of a file inside a Change Set in a RTC precondition

IServerSideVersionedContentService contentService =
  (IServerSideVersionedContentService) getService(IServerSideVersionedContentService.class);
ByteArrayOutputStream out = new ByteArrayOutputStream();
contentService.fetchContentTrusted(file,content.getHash(), out);

But with the method fetchContentTrusted I get always the whole file. What I would need, due to performance issues, is only to fetch the first n bytes. Is there a way to get only the first n bytes instead of the whole content?

Thanks and regards

Martin