code: public static Observable<byte[]> from(InputStream is, int size) {
          return Observable.create(new OnSubscribeInputStream(is, size));
      }
docs: Returns an Observable stream of byte arrays from the given
  {@link InputStream} between 1 and {@code size} bytes.
  
  @param is
  input stream of bytes
  @param size
  max emitted byte array size
  @return a stream of byte arrays