refactor: remove crc32 dependency

package.json

@@ -28,7 +28,6 @@
 		"test:watch": "TS_NODE_TRANSPILE_ONLY=true node --test --watch --loader=ts-node/esm --no-warnings src/*.test.ts"
 	},
 	"dependencies": {
-		"crc-32": "~1.2.0",
 		"lzma1": "0.0.2",
 		"validator": "^13.12.0"
 	},

src/crc32.test.ts

@@ -0,0 +1,30 @@
+import { strict as assert } from "node:assert";
+import test, { describe } from "node:test";
+
+import { crc32 } from "./crc32.js";
+
+describe("crc32", () => {
+	test("empty string", () => {
+		const result = crc32("");
+		assert.equal(result, 0);
+	});
+
+	test('"123456789"', () => {
+		const result = crc32("123456789");
+		const expected = 0xCBF43926;
+		assert.equal(result, expected);
+	});
+
+	test('"Hello, World!"', () => {
+		const result = crc32("Hello, World!");
+		const expected = 0xEC4AC3D0;
+		assert.equal(result, expected);
+	});
+
+	test("a long string", () => {
+		const longString = "a".repeat(1000);
+		const result = crc32(longString);
+		const expected = 0x9A38DA03;
+		assert.equal(result, expected);
+	});
+});

src/crc32.ts

@@ -0,0 +1,21 @@
+// Precomputed CRC32 lookup table
+const LOOKUP_TABLE = new Uint32Array(256);
+
+for (let i = 0; i < LOOKUP_TABLE.length; i++) {
+	let crc = i;
+	for (let j = 0; j < 8; j++) {
+		crc = (crc >>> 1) ^ (0xEDB88320 * (crc & 1));
+	}
+	LOOKUP_TABLE[i] = crc;
+}
+
+export function crc32(data: string): number {
+	let crc = 0 ^ (-1);
+	const encoded = new TextEncoder().encode(data);
+
+	for (let i = 0; i < encoded.length; i++) {
+		crc = (crc >>> 8) ^ LOOKUP_TABLE[(crc ^ encoded[i]) & 0xFF];
+	}
+
+	return (crc ^ (-1)) >>> 0;
+}

src/encode.ts

@@ -1,7 +1,7 @@
-import crc32 from "crc-32";
 import { compress } from "lzma1";
 
 import * as base32hex from "./base32hex.js";
+import { crc32 } from "./crc32.js";
 import { deburr } from "./deburr.js";
 import {
 	DataModel,
@@ -88,7 +88,7 @@ export function headerDataLength(length: number): Uint8Array {
  */
 export function addChecksum(serialized: string): Uint8Array {
 	const checksum = new ArrayBuffer(4);
-	new DataView(checksum).setUint32(0, crc32.str(serialized), true);
+	new DataView(checksum).setUint32(0, crc32(serialized), true);
 
 	const byteArray = new TextEncoder().encode(serialized);