void readWrite(SomethingHead head);

default byte[] saveToByteArray aka saveAsByteArray aka toByteArray(SomethingHead head default new) {
  var baos = byteArrayOutputStream();
  head.outputStream(baos);
  readWrite(head);
  head.finish();
  ret baos.toByteArray();
}

default S toHexString() {
  ret main toHexString(toByteArray());
}

default File saveToFile(File file) {
  temp OutputStream out = bufferedFileOutputStream(file);
  var head = new SomethingHead(out);
  readWrite(head);
  head.finish();
  ret file;
}

default selfType load aka fromByteArray(byte[] data) {
  readWrite(new SomethingHead(new ByteArrayInputStream(data)));
  this;
}

default selfType load(File file) {
  temp InputStream in = bufferedInputStream(file);
  readWrite(new SomethingHead(in));
  this;
}

default long byteIOLength() {
  new JustCountingOutputStream out;
  var head = new SomethingHead(out);
  readWrite(head);
  head.finish();
  ret out!;
}

Began life as a copy of #1035635