feat: add method to return Zniffer capture as Buffer (#6836)

Co-authored-by: Dominic Griesel <[email protected]>

docs/api/zniffer.md

@@ -104,6 +104,12 @@ When done, make sure to destroy the Zniffer instance to release the serial port
 await zniffer.destroy();
 ```
 
+Captured frames can also be returned as a `Buffer` in the `.zlf` format using the `getCaptureAsZLFBuffer` method:
+
+```ts
+await zniffer.getCaptureAsZLFBuffer();
+```
+
 ## Frequency selection
 
 The configured frequency of the Zniffer has to match the frequency of the Z-Wave network it is capturing. Zniffers based on 700/800 series firmware support frequencies that match the `ZnifferRegion` enum:

packages/zwave-js/src/lib/zniffer/Zniffer.ts

@@ -851,17 +851,21 @@ export class Zniffer extends TypedEventEmitter<ZnifferEventCallbacks> {
 		this._capturedFrames = [];
 	}
 
-	/** Saves the captured frames in a `.zlf` file that can be read by the official Zniffer application. */
-	public async saveCaptureToFile(filePath: string): Promise<void> {
+	/** Get the captured frames in the official Zniffer application format. */
+	public getCaptureAsZLFBuffer(): Buffer {
 		// Mimics the current Zniffer software, without using features like sessions and comments
 		const header = Buffer.alloc(2048, 0);
 		header[0] = 0x68; // zniffer version
 		header.writeUInt16BE(0x2312, 0x07fe); // checksum
+		return Buffer.concat([
+			header,
+			...this._capturedFrames.map(captureToZLFEntry),
+		]);
+	}
 
-		await fs.writeFile(filePath, header);
-		for (const frame of this._capturedFrames) {
-			await fs.appendFile(filePath, captureToZLFEntry(frame));
-		}
+	/** Saves the captured frames in a `.zlf` file that can be read by the official Zniffer application. */
+	public async saveCaptureToFile(filePath: string): Promise<void> {
+		await fs.writeFile(filePath, this.getCaptureAsZLFBuffer());
 	}
 
 	/**