Revert "refactor(bytes): remove equalsNaive (#2852)" (#2854)

bytes/equals.ts

@@ -1,11 +1,25 @@
 // Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
 // This module is browser compatible.
 
-/** Check whether binary arrays are equal to each other.
+/** Check whether binary arrays are equal to each other using 8-bit comparisons.
+ * @private
  * @param a first array to check equality
  * @param b second array to check equality
  */
-export function equals(a: Uint8Array, b: Uint8Array): boolean {
+export function equalsNaive(a: Uint8Array, b: Uint8Array): boolean {
+  if (a.length !== b.length) return false;
+  for (let i = 0; i < b.length; i++) {
+    if (a[i] !== b[i]) return false;
+  }
+  return true;
+}
+
+/** Check whether binary arrays are equal to each other using 32-bit comparisons.
+ * @private
+ * @param a first array to check equality
+ * @param b second array to check equality
+ */
+export function equals32Bit(a: Uint8Array, b: Uint8Array): boolean {
   if (a.length !== b.length) return false;
   const len = a.length;
   const compressable = Math.floor(len / 4);
@@ -19,3 +33,12 @@ export function equals(a: Uint8Array, b: Uint8Array): boolean {
   }
   return true;
 }
+
+/** Check whether binary arrays are equal to each other.
+ * @param a first array to check equality
+ * @param b second array to check equality
+ */
+export function equals(a: Uint8Array, b: Uint8Array): boolean {
+  if (a.length < 1000) return equalsNaive(a, b);
+  return equals32Bit(a, b);
+}

bytes/equals_bench.ts

@@ -0,0 +1,35 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+import { equals32Bit, equalsNaive } from "./equals.ts";
+
+console.log("generating benchmarks...");
+const testCases: [Uint8Array, Uint8Array][] = [];
+// CHANGE THESE
+const len = 10000;
+const nCases = 10000;
+for (let i = 0; i < nCases; i++) {
+  const arr1 = crypto.getRandomValues(new Uint8Array(len));
+  const arr2 = crypto.getRandomValues(new Uint8Array(len));
+  const arr3 = arr1.slice(0);
+  arr3[arr3.length - 1] = arr1[arr1.length - 1] ^ 1;
+  testCases.push([arr1, arr1.slice(0)]);
+  testCases.push([arr1, arr2]);
+  testCases.push([arr1, arr3]);
+}
+
+Deno.bench({
+  name: "bench old equals",
+  fn() {
+    for (const [a, b] of testCases) {
+      equalsNaive(a, b);
+    }
+  },
+});
+
+Deno.bench({
+  name: "bench simd equals",
+  fn() {
+    for (const [a, b] of testCases) {
+      equals32Bit(a, b);
+    }
+  },
+});