static byte[] byteArrayFromShorts_bigEndian(short[] a) {
  ret byteArrayFromShorts_bigEndian(a, 0, l(a));
}

static byte[] byteArrayFromShorts_bigEndian(short[] a, int from, int to) {
  byte[] b = new byte[(to-from)*2];
  for (int i = 0; i < a.length; i++) {
    short s = a[from+i];
    b[i*2] = (byte) (s >> 8);
    b[i*2+1] = (byte) s;
  }
  ret b;
}