Class Grid

ch5-game-of-life/thread-gol.js:1–43

class Grid {
  constructor(size, buffer, paint = () => {}) {
    const sizeSquared = size * size;
    this.buffer = buffer;
    this.size = size;
    this.cells = new Uint8Array(this.buffer, 0, sizeSquared);
    this.nextCells = new Uint8Array(this.buffer, sizeSquared, sizeSquared);
    this.paint = paint;
  }

  getCell(x, y) {
    const size = this.size;
    const sizeM1 = size - 1;
    x = x < 0 ? sizeM1 : x > sizeM1 ? 0 : x;
    y = y < 0 ? sizeM1 : y > sizeM1 ? 0 : y;
    return this.cells[size * x + y];
  }

  static NEIGHBORS = [
    [-1, -1], [-1, 0], [-1, 1], [0, -1], [0, 1], [1, -1], [1, 0], [1, 1]
  ];

  iterate(minX, minY, maxX, maxY) {
    const size = this.size;

    for (let x = minX; x < maxX; x++) {
      for (let y = minY; y < maxY; y++) {
        const cell = this.cells[size * x + y];
        let alive = 0;
        for (const [i, j] of Grid.NEIGHBORS) {
          alive += this.getCell(x + i, y + j);
        }
        const newCell = alive === 3 || (cell && alive === 2) ? 1 : 0;
        this.nextCells[size * x + y] = newCell;
        this.paint(newCell, x, y);
      }
    }

    const cells = this.nextCells;
    this.nextCells = this.cells;
    this.cells = cells;
  }
}

const BLACK = 0xFF000000;
const WHITE = 0xFFFFFFFF;