@thi.ng/grid-iterators/hilbert.js

2D grid and shape iterators w/ multiple orderings

import { __opts } from "./utils.js";
function* hilbert2d(opts) {
  const { cols, rows, tx } = __opts(opts);
  let hIndex = 0;
  let hOrder = 0;
  while ((1 << hOrder < cols || 1 << hOrder < rows) && hOrder < 15) hOrder++;
  const numBuckets = 1 << 2 * hOrder;
  for (let i = 0, n = cols * rows; i < n; i++) {
    let hx, hy;
    do {
      let s, t, comp, swap, cs, sr;
      s = hIndex | 1431655765 << 2 * hOrder;
      sr = s >>> 1 & 1431655765;
      cs = (s & 1431655765) + sr ^ 1431655765;
      cs = cs ^ cs >>> 2;
      cs = cs ^ cs >>> 4;
      cs = cs ^ cs >>> 8;
      cs = cs ^ cs >>> 16;
      swap = cs & 1431655765;
      comp = cs >>> 1 & 1431655765;
      t = s & swap ^ comp;
      s = s ^ sr ^ t ^ t << 1;
      s = s & (1 << 2 * hOrder) - 1;
      t = (s ^ s >>> 1) & 572662306;
      s = s ^ t ^ t << 1;
      t = (s ^ s >>> 2) & 202116108;
      s = s ^ t ^ t << 2;
      t = (s ^ s >>> 4) & 15728880;
      s = s ^ t ^ t << 4;
      t = (s ^ s >>> 8) & 65280;
      s = s ^ t ^ t << 8;
      hx = s >>> 16;
      hy = s & 65535;
      hIndex++;
    } while (
      // Dont't emit any outside cells
      (hx >= cols || hy >= rows || hx < 0 || hy < 0) && hIndex < numBuckets
    );
    yield tx(hx, hy);
  }
}
export {
  hilbert2d
};