Optimization of websocket masking about undici HOT 9 CLOSED

import { randomBytes } from "crypto";
import { group, bench, run } from "mitata";

function maskForOne(mask, buffer) {
  const alloc = Buffer.allocUnsafe(buffer.length);
  for (let i = 0; i < buffer.length; ++i) {
    alloc[i] = buffer[i] ^ mask[i & 3];
  }
  return alloc;
}

function maskForFour(mask, buffer) {
  const length = buffer.length;
  const alloc = Buffer.allocUnsafe(buffer.length);
  const lengthFor4 = length - (length & 3);
  if (length > 3) {
    for (let i = 0; i < lengthFor4; i += 4) {
      alloc[i] = buffer[i] ^ mask[0];
      alloc[i + 1] = buffer[i + 1] ^ mask[1];
      alloc[i + 2] = buffer[i + 2] ^ mask[2];
      alloc[i + 3] = buffer[i + 3] ^ mask[3];
    }
  }
  for (let i = lengthFor4; i < length; ++i) {
    alloc[i] = buffer[i] ^ mask[i & 3];
  }
  return alloc;
}

group("mask", () => {
  const buffer = new Uint8Array(randomBytes(1024 * 4).buffer);
  const mask = new Uint8Array(randomBytes(4).buffer);
  bench("for 1", () => maskForOne(mask, buffer));
  bench("for 4", () => maskForFour(mask, buffer));
});

await run();

switch (length & 3) {
  case 3:
    buffer[i + 3] ^ mask[3]
  case 2:
    buffer[i + 2] ^ mask[2]
  case 2:
    buffer[i + 1] ^ mask[1]
  ...