// from https://stackoverflow.com/questions/664014/what-integer-hash-function-are-good-that-accepts-an-integer-hash-key
// reverse of scrambleInt
static int unscrambleInt(int x) {
  x = ((x >>> 16) ^ x) * 0x119de1f3;
  x = ((x >>> 16) ^ x) * 0x119de1f3;
  x = (x >>> 16) ^ x;
  ret x;
}

Began life as a copy of #1034916