⚡️ uint8array set method instead of spread (#1667)

Hello @coyotte508 

I stumbled upon this
[issue](#1280).

I suggest to use the
[set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/set)
method instead.

Benchmark: https://jsben.ch/jze3P

---------

Co-authored-by: VivianHublo <[email protected]>

Author: vvnsrzn

packages/hub/src/utils/XetBlob.ts

@@ -1,6 +1,7 @@
 import { createApiError } from "../error";
 import type { CredentialsParams } from "../types/public";
 import { checkCredentials } from "./checkCredentials";
+import { combineUint8Arrays } from "./combineUint8Arrays";
 import { decompress as lz4_decompress } from "../vendor/lz4js";
 import { RangeList } from "./RangeList";
 
@@ -327,11 +328,11 @@ export class XetBlob extends Blob {
 					totalFetchBytes += result.value.byteLength;
 
 					if (leftoverBytes) {
-						result.value = new Uint8Array([...leftoverBytes, ...result.value]);
+						result.value = combineUint8Arrays(leftoverBytes, result.value);
 						leftoverBytes = undefined;
 					}
 
-					while (totalBytesRead < maxBytes && result.value.byteLength) {
+					while (totalBytesRead < maxBytes && result.value?.byteLength) {
 						if (result.value.byteLength < 8) {
 							// We need 8 bytes to parse the chunk header
 							leftoverBytes = result.value;

packages/hub/src/utils/combineUint8Arrays.spec.ts

@@ -0,0 +1,15 @@
+import { describe, it, expect } from "vitest";
+import { combineUint8Arrays } from "./combineUint8Arrays";
+
+describe("combineUint8Arrays", () => {
+	it.each([
+		{ a: [], b: [], expected: [] },
+		{ a: [], b: [1, 2, 3], expected: [1, 2, 3] },
+		{ a: [4, 5, 6], b: [], expected: [4, 5, 6] },
+		{ a: [7, 8], b: [9, 10], expected: [7, 8, 9, 10] },
+		{ a: [1], b: [2, 3, 4], expected: [1, 2, 3, 4] },
+	])("combines $a and $b to $expected", ({ a, b, expected }) => {
+		const result = combineUint8Arrays(new Uint8Array(a), new Uint8Array(b));
+		expect(result).toEqual(new Uint8Array(expected));
+	});
+});

packages/hub/src/utils/combineUint8Arrays.ts

@@ -0,0 +1,10 @@
+export function combineUint8Arrays(
+	a: Uint8Array<ArrayBufferLike>,
+	b: Uint8Array<ArrayBufferLike>
+): Uint8Array<ArrayBuffer> {
+	const aLength = a.length;
+	const combinedBytes = new Uint8Array(aLength + b.length);
+	combinedBytes.set(a);
+	combinedBytes.set(b, aLength);
+	return combinedBytes;
+}