feat: add getUintBE, findSequence, and encoding for uint8ArrayToString

index.d.ts

@@ -121,7 +121,7 @@ const array3 = new Uint8Array([7, 8, 9]);
 export function compareUint8Arrays(a: Uint8Array, b: Uint8Array): 0 | 1 | -1;
 
 /**
-Convert a `Uint8Array` (containing a UTF-8 string) to a string.
+Convert a `Uint8Array` to a string using an optional encoding (defaults to UTF-8).
 
 Replacement for [`Buffer#toString()`](https://nodejs.org/api/buffer.html#buftostringencoding-start-end).
 
@@ -135,7 +135,7 @@ console.log(uint8ArrayToString(byteArray));
 //=> 'Hello'
 ```
 */
-export function uint8ArrayToString(array: Uint8Array): string;
+export function uint8ArrayToString(array: Uint8Array, encoding?: string): string;
 
 /**
 Convert a string to a `Uint8Array` (using UTF-8 encoding).
@@ -249,3 +249,17 @@ console.log(hexToUint8Array('48656c6c6f'));
 ```
 */
 export function hexToUint8Array(hexString: string): Uint8Array;
+
+/**
+Get up to a 48-bit integer from a DataView`
+
+Replacement for [`Buffer#readUintBE`](https://nodejs.org/api/buffer.html#bufreadintbeoffset-bytelength)
+*/
+export function getUintBE(view: DataView): number; // eslint-disable-line @typescript-eslint/naming-convention
+
+/**
+ * Find a sequence of bytes in an array buffer
+ *
+ * Replacement for [`Buffer#indexOf`](https://nodejs.org/api/buffer.html#bufindexofvalue-byteoffset-encoding)
+ */
+export function findSequence(arrayBuffer: ArrayBuffer, sequence: Uint8Array): number;

index.js

@@ -90,11 +90,14 @@ export function compareUint8Arrays(a, b) {
 	return Math.sign(a.length - b.length);
 }
 
-const cachedDecoder = new globalThis.TextDecoder();
+const cachedDecoders = {
+	utf8: new globalThis.TextDecoder('utf8'),
+};
 
-export function uint8ArrayToString(array) {
+export function uint8ArrayToString(array, encoding = 'utf8') {
 	assertUint8Array(array);
-	return cachedDecoder.decode(array);
+	cachedDecoders[encoding] ??= new globalThis.TextDecoder(encoding);
+	return cachedDecoders[encoding].decode(array);
 }
 
 function assertString(value) {
@@ -220,3 +223,63 @@ export function hexToUint8Array(hexString) {
 
 	return bytes;
 }
+
+/**
+ * @param {DataView} view
+ * @returns {number}
+ */
+export function getUintBE(view) {
+	const {byteLength} = view;
+
+	if (byteLength === 6) {
+		return (view.getUint16(0) * (2 ** 32)) + view.getUint32(2);
+	}
+
+	if (byteLength === 5) {
+		return (view.getUint8(0) * (2 ** 32)) + view.getUint32(1);
+	}
+
+	if (byteLength === 4) {
+		return view.getUint32(0);
+	}
+
+	if (byteLength === 3) {
+		return (view.getUint8(0) * (2 ** 16)) + view.getUint16(1);
+	}
+
+	if (byteLength === 2) {
+		return view.getUint16(0);
+	}
+
+	if (byteLength === 1) {
+		return view.getUint8(0);
+	}
+}
+
+/**
+ * @param {Uint8Array} arrayBuffer
+ * @param {Uint8Array} sequence
+ * @returns {number}
+ */
+export function findSequence(arrayBuffer, sequence) {
+	const sequenceLength = sequence.length;
+	const validOffsetLength = arrayBuffer.length - sequenceLength;
+
+	for (let i = 0; i < validOffsetLength; i += 1) {
+		let match = true;
+
+		for (let j = 0; j < sequenceLength; j += 1) {
+			if (arrayBuffer[i + j] !== sequence[j]) {
+				match = false;
+				j = 0;
+				break;
+			}
+		}
+
+		if (match) {
+			return i;
+		}
+	}
+
+	return -1;
+}

test.js

@@ -14,6 +14,8 @@ import {
 	base64ToString,
 	uint8ArrayToHex,
 	hexToUint8Array,
+	getUintBE,
+	findSequence,
 } from './index.js';
 
 test('isUint8Array', t => {
@@ -119,6 +121,12 @@ test('stringToUint8Array and uint8ArrayToString', t => {
 	t.is(uint8ArrayToString(array), fixture);
 });
 
+test('uint8ArrayToString with encoding', t => {
+	t.is(uint8ArrayToString(new Uint8Array([
+		207, 240, 232, 226, 229, 242, 44, 32, 236, 232, 240, 33,
+	]), 'windows-1251'), 'Привет, мир!');
+});
+
 test('uint8ArrayToBase64 and base64ToUint8Array', t => {
 	const fixture = stringToUint8Array('Hello');
 	const base64 = uint8ArrayToBase64(fixture);
@@ -158,3 +166,25 @@ test('hexToUint8Array', t => {
 	const fixtureHex = Buffer.from(fixtureString).toString('hex'); // eslint-disable-line n/prefer-global/buffer
 	t.deepEqual(hexToUint8Array(fixtureHex), new Uint8Array(Buffer.from(fixtureHex, 'hex'))); // eslint-disable-line n/prefer-global/buffer
 });
+
+test('getUintBE', t => {
+	const fixture = [0x12, 0x34, 0x56, 0x78, 0x90, 0xab]; // eslint-disable-line unicorn/number-literal-case
+
+	for (let i = 1; i < 6; i += 1) {
+		t.is(getUintBE(new DataView(new Uint8Array(fixture).buffer, 0, i)), Buffer.from(fixture).readUintBE(0, i)); // eslint-disable-line n/prefer-global/buffer
+	}
+
+	for (let i = 0; i < 5; i += 1) {
+		t.is(getUintBE(new DataView(new Uint8Array(fixture).buffer, i, 6 - i)), Buffer.from(fixture).readUintBE(i, 6 - i)); // eslint-disable-line n/prefer-global/buffer
+	}
+});
+
+test('findSequence', t => {
+	const fixture = [0x12, 0x34, 0x56, 0x78, 0x90, 0xab, 0xcd, 0xef]; // eslint-disable-line unicorn/number-literal-case
+	const sequence = [0x78, 0x90];
+	t.is(findSequence(new Uint8Array(fixture), new Uint8Array(sequence)), Buffer.from(fixture).indexOf(Buffer.from(sequence))); // eslint-disable-line n/prefer-global/buffer
+	t.is(findSequence(new Uint8Array(fixture), new Uint8Array(sequence)), 3);
+	t.is(findSequence(new Uint8Array(fixture), new Uint8Array([0x00, 0x01])), -1);
+	// Uint8Array only works with a number so it cannot replace Buffer.indexOf
+	t.not(new Uint8Array(fixture).indexOf(new Uint8Array(sequence)), Buffer.from(fixture).indexOf(Buffer.from(sequence))); // eslint-disable-line n/prefer-global/buffer
+});