Make conversion cancelable

src/output.ts

@@ -86,8 +86,26 @@ export class Output<
 	/** @internal */
 	_finalizing = false;
 	/** @internal */
+	_finalized = false;
+	/** @internal */
 	_mutex = new AsyncMutex();
 
+	get isStarted() {
+		return this._started;
+	}
+
+	get isCanceled() {
+		return this._canceled;
+	}
+
+	get isFinalizing() {
+		return this._finalizing;
+	}
+
+	get isFinalized() {
+		return this._finalized;
+	}
+
 	constructor(options: OutputOptions<F, T>) {
 		if (!options || typeof options !== 'object') {
 			throw new TypeError('options must be an object.');
@@ -334,6 +352,8 @@ export class Output<
 		await this._writer.flush();
 		await this._writer.finalize();
 
+		this._finalized = true;
+
 		release();
 	}
 }