Add ability to abort async operations (#667)

Co-authored-by: Sindre Sorhus <[email protected]>

core.d.ts

@@ -491,7 +491,7 @@ export function fileTypeStream(webStream: AnyWebReadableStream<Uint8Array>, opti
 export declare class FileTypeParser {
 	detectors: Iterable<Detector>;
 
-	constructor(options?: {customDetectors?: Iterable<Detector>});
+	constructor(options?: {customDetectors?: Iterable<Detector>; signal: AbortSignal});
 
 	/**
 	Works the same way as {@link fileTypeFromBuffer}, additionally taking into account custom detectors (if any were provided to the constructor).

core.js

@@ -58,7 +58,9 @@ export async function fileTypeStream(webStream, options) {
 export class FileTypeParser {
 	constructor(options) {
 		this.detectors = options?.customDetectors;
-
+		this.tokenizerOptions = {
+			abortSignal: options?.signal,
+		};
 		this.fromTokenizer = this.fromTokenizer.bind(this);
 		this.fromBuffer = this.fromBuffer.bind(this);
 		this.parse = this.parse.bind(this);
@@ -92,15 +94,15 @@ export class FileTypeParser {
 			return;
 		}
 
-		return this.fromTokenizer(strtok3.fromBuffer(buffer));
+		return this.fromTokenizer(strtok3.fromBuffer(buffer, this.tokenizerOptions));
 	}
 
 	async fromBlob(blob) {
 		return this.fromStream(blob.stream());
 	}
 
 	async fromStream(stream) {
-		const tokenizer = await strtok3.fromWebStream(stream);
+		const tokenizer = await strtok3.fromWebStream(stream, this.tokenizerOptions);
 		try {
 			return await this.fromTokenizer(tokenizer);
 		} finally {

index.js

@@ -9,7 +9,7 @@ import {FileTypeParser, reasonableDetectionSizeInBytes} from './core.js';
 
 export class NodeFileTypeParser extends FileTypeParser {
 	async fromStream(stream) {
-		const tokenizer = await (stream instanceof WebReadableStream ? strtok3.fromWebStream(stream) : strtok3.fromStream(stream));
+		const tokenizer = await (stream instanceof WebReadableStream ? strtok3.fromWebStream(stream, this.tokenizerOptions) : strtok3.fromStream(stream, this.tokenizerOptions));
 		try {
 			return super.fromTokenizer(tokenizer);
 		} finally {

package.json

@@ -220,7 +220,7 @@
 	],
 	"dependencies": {
 		"get-stream": "^9.0.1",
-		"strtok3": "^8.1.0",
+		"strtok3": "^9.0.0",
 		"token-types": "^6.0.0",
 		"uint8array-extras": "^1.3.0"
 	},

readme.md

@@ -367,6 +367,22 @@ const fileType = await parser.fromBuffer(buffer);
 console.log(fileType);
 ```
 
+## Abort signal
+
+Some async operations can be aborted by passing an [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) to the `FileTypeParser` constructor.
+
+```js
+import {FileTypeParser} from 'file-type'; // or `NodeFileTypeParser` in Node.js
+
+const abortController = new AbortController()
+
+const parser = new FileTypeParser({abortSignal: abortController.signal});
+
+const promise = parser.fromStream(blob.stream());
+
+abortController.abort(); // Abort file-type reading from the Blob stream.
+```
+
 ## Supported file types
 
 - [`3g2`](https://en.wikipedia.org/wiki/3GP_and_3G2#3G2) - Multimedia container format defined by the 3GPP2 for 3G CDMA2000 multimedia services

test.js

@@ -466,6 +466,26 @@ test('.fileTypeStream() method - sampleSize option', async t => {
 	t.is(stream.fileType.mime, 'video/ogg');
 });
 
+test('.fileTypeFromStream() method - be able to abort operation', async t => {
+	const bufferA = new Uint8Array([0, 1, 0, 1]);
+	class MyStream extends stream.Readable {
+		_read() {
+			setTimeout(() => {
+				this.push(bufferA);
+				this.push(null);
+			}, 500);
+		}
+	}
+
+	const shortStream = new MyStream();
+	const abortController = new AbortController();
+	const parser = new NodeFileTypeParser({signal: abortController.signal});
+	const promiseFileType = parser.fromStream(shortStream);
+	abortController.abort(); // Abort asynchronous operation: reading from shortStream
+	const error = await t.throwsAsync(promiseFileType);
+	t.is(error.message, 'Stream closed');
+});
+
 test('supportedExtensions.has', t => {
 	t.true(supportedExtensions.has('jpg'));
 	t.false(supportedExtensions.has('blah'));