static byte[] toByteArray(ByteArrayOutputStream baos) {
  ret baos == null ? null : baos.toByteArray();
}

static byte[] toByteArray(Iterator<? extends Number> it) {
  new ByteBuffer buf;
  while (it.hasNext())
    buf.add((byte) it.next().intValue());
  ret buf.toByteArray();
}

static byte[] toByteArray(Cl<? extends Number> it) {
  int n = l(it), i = 0;
  byte[] a = new[n];
  for (x : it)
    a[i++] = (byte) x.intValue();
  ret a;
}

static byte[] toByteArray(O o) {
  if (o == null) null;
  if (o cast byte[]) ret o;
  if (o instanceof Iterator)
    ret toByteArray((Iterator<Number>) o);
  if (o cast Cl)
    ret toByteArray((Cl<Number>) o);
  // not sure what else to put here
  fail("toByteArray", o);
}

// Note: Does not rewind the buffer
static byte[] toByteArray(java.nio.ByteBuffer buf) {
  if (buf == null) null;
  byte[] a = new[buf.remaining()];
  buf.get(a);
  ret a;
}