util: add matching bytes length util from verkle

packages/util/src/bytes.ts

@@ -551,3 +551,26 @@ export { bytesToUtf8, equalsBytes, utf8ToBytes } from 'ethereum-cryptography/uti
 export function hexToBigInt(input: PrefixedHexString): bigint {
   return bytesToBigInt(hexToBytes(isHexString(input) ? input : `0x${input}`))
 }
+
+/**
+ * Compares two byte arrays and returns the count of consecutively matching items from the start.
+ *
+ * @function
+ * @param {Uint8Array} bytes1 - The first Uint8Array to compare.
+ * @param {Uint8Array} bytes2 - The second Uint8Array to compare.
+ * @returns {number} The count of consecutively matching items from the start.
+ */
+export function matchingBytesLength(bytes1: Uint8Array, bytes2: Uint8Array): number {
+  let count = 0
+  const minLength = Math.min(bytes1.length, bytes2.length)
+
+  for (let i = 0; i < minLength; i++) {
+    if (bytes1[i] === bytes2[i]) {
+      count++
+    } else {
+      // Break early if a mismatch is found
+      break
+    }
+  }
+  return count
+}

packages/util/test/bytes.spec.ts

@@ -17,6 +17,7 @@ import {
   intToHex,
   intToUnpaddedBytes,
   isZeroAddress,
+  matchingBytesLength,
   setLengthLeft,
   setLengthRight,
   short,
@@ -482,3 +483,47 @@ describe('unprefixedHexToBytes', () => {
     assert.deepEqual(converted, new Uint8Array([17]))
   })
 })
+
+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)
+  })
+})