From 3f9be25aada4be24591dfc71b43b7275c1c18cd1 Mon Sep 17 00:00:00 2001
From: Scorbajio <indigophi@protonmail.com>
Date: Mon, 10 Jun 2024 05:59:47 -0700
Subject: [PATCH] verkle: Add tests for verkle bytes helper (#3441)

* Add tests for verkle bytes helper

* Optimize matchingBytesLength

---------

Co-authored-by: acolytec3 <17355484+acolytec3@users.noreply.github.com>
---
 packages/verkle/src/util/bytes.ts       | 22 +++++++++---
 packages/verkle/test/util/bytes.spec.ts | 47 +++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 4 deletions(-)
 create mode 100644 packages/verkle/test/util/bytes.spec.ts

diff --git a/packages/verkle/src/util/bytes.ts b/packages/verkle/src/util/bytes.ts
index 9a5b83da93..a3d1bc5938 100644
--- a/packages/verkle/src/util/bytes.ts
+++ b/packages/verkle/src/util/bytes.ts
@@ -8,15 +8,29 @@
  */
 export function matchingBytesLength(bytes1: Uint8Array, bytes2: Uint8Array): number {
   let count = 0
-
-  // The minimum length of both arrays
   const minLength = Math.min(bytes1.length, bytes2.length)
 
-  for (let i = 0; i < minLength; i++) {
+  // Unroll the loop for better performance
+  for (let i = 0; i < minLength - 3; i += 4) {
+    // Compare 4 bytes at a time
+    if (
+      bytes1[i] === bytes2[i] &&
+      bytes1[i + 1] === bytes2[i + 1] &&
+      bytes1[i + 2] === bytes2[i + 2] &&
+      bytes1[i + 3] === bytes2[i + 3]
+    ) {
+      count += 4
+    } else {
+      // Break early if a mismatch is found
+      break
+    }
+  }
+
+  // Handle any remaining elements
+  for (let i = minLength - (minLength % 4); i < minLength; i++) {
     if (bytes1[i] === bytes2[i]) {
       count++
     } else {
-      // Stop counting as soon as a mismatch is found
       break
     }
   }
diff --git a/packages/verkle/test/util/bytes.spec.ts b/packages/verkle/test/util/bytes.spec.ts
new file mode 100644
index 0000000000..850a2bdb14
--- /dev/null
+++ b/packages/verkle/test/util/bytes.spec.ts
@@ -0,0 +1,47 @@
+import { assert, describe, it } from 'vitest'
+
+import { matchingBytesLength } from '../../src/util/bytes.js'
+
+describe('matchingBytesLength', () => {
+  it('should return 0 when both arrays are empty', () => {
+    const bytes1 = new Uint8Array([])
+    const bytes2 = new Uint8Array([])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 0)
+  })
+
+  it('should return 0 when one of the arrays is empty', () => {
+    const bytes1 = new Uint8Array([1, 2, 3])
+    const bytes2 = new Uint8Array([])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 0)
+  })
+
+  it('should return 0 when arrays have no matching elements', () => {
+    const bytes1 = new Uint8Array([1, 2, 3])
+    const bytes2 = new Uint8Array([4, 5, 6])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 0)
+  })
+
+  it('should handle arrays with same elements but different lengths', () => {
+    const bytes1 = new Uint8Array([1, 2, 3])
+    const bytes2 = new Uint8Array([1, 2, 3, 4])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 3)
+  })
+
+  it('should handle arrays with matching elements at end', () => {
+    const bytes1 = new Uint8Array([1, 2, 3])
+    const bytes2 = new Uint8Array([0, 1, 2, 3])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 0)
+  })
+
+  it('should handle arrays with matching elements at start', () => {
+    const bytes1 = new Uint8Array([1, 2, 3])
+    const bytes2 = new Uint8Array([1, 2, 3, 4, 5])
+    assert.equal(matchingBytesLength(bytes1, bytes2), 3)
+  })
+
+  it('should handle arrays with large number of elements', () => {
+    const bytes1 = new Uint8Array(Array.from({ length: 1000000 }, (_, i) => i))
+    const bytes2 = new Uint8Array(Array.from({ length: 1000000 }, (_, i) => i))
+    assert.equal(matchingBytesLength(bytes1, bytes2), 1000000)
+  })
+})