How to use the @sindresorhus/is.buffer function in @sindresorhus/is

}

		opts.path = `${opts.path.split('?')[0]}?${opts.query}`;
		delete opts.query;
	}

	if (opts.json && is.undefined(opts.headers.accept)) {
		opts.headers.accept = 'application/json';
	}

	const body = opts.body;
	if (is.nullOrUndefined(body)) {
		opts.method = (opts.method || 'GET').toUpperCase();
	} else {
		const headers = opts.headers;
		if (!is.nodeStream(body) && !is.string(body) && !is.buffer(body) && !(opts.form || opts.json)) {
			throw new TypeError('The `body` option must be a stream.Readable, string, Buffer or plain Object');
		}

		const canBodyBeStringified = is.plainObject(body) || is.array(body);
		if ((opts.form || opts.json) && !canBodyBeStringified) {
			throw new TypeError('The `body` option must be a plain Object or Array when the `form` or `json` option is used');
		}

		if (isFormData(body)) {
			// Special case for https://github.com/form-data/form-data
			headers['content-type'] = headers['content-type'] || `multipart/form-data; boundary=${body.getBoundary()}`;
		} else if (opts.form && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
			opts.body = querystring.stringify(body);
		} else if (opts.json && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/json';

}

		opts.path = `${opts.path.split('?')[0]}?${opts.query}`;
		delete opts.query;
	}

	if (opts.json && is.undefined(opts.headers.accept)) {
		opts.headers.accept = 'application/json';
	}

	const body = opts.body;
	if (is.nullOrUndefined(body)) {
		opts.method = (opts.method || 'GET').toUpperCase();
	} else {
		const headers = opts.headers;
		if (!is.nodeStream(body) && !is.string(body) && !is.buffer(body) && !(opts.form || opts.json)) {
			throw new TypeError('The `body` option must be a stream.Readable, string, Buffer or plain Object');
		}

		const canBodyBeStringified = is.plainObject(body) || is.array(body);
		if ((opts.form || opts.json) && !canBodyBeStringified) {
			throw new TypeError('The `body` option must be a plain Object or Array when the `form` or `json` option is used');
		}

		if (isFormData(body)) {
			// Special case for https://github.com/form-data/form-data
			headers['content-type'] = headers['content-type'] || `multipart/form-data; boundary=${body.getBoundary()}`;
		} else if (opts.form && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
			opts.body = querystring.stringify(body);
		} else if (opts.json && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/json';

} else if (opts.form && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/x-www-form-urlencoded';
			opts.body = querystring.stringify(body);
		} else if (opts.json && canBodyBeStringified) {
			headers['content-type'] = headers['content-type'] || 'application/json';
			opts.body = JSON.stringify(body);
		}

		if (is.undefined(headers['content-length']) && is.undefined(headers['transfer-encoding']) && !is.nodeStream(body)) {
			const length = is.string(opts.body) ? Buffer.byteLength(opts.body) : opts.body.length;
			headers['content-length'] = length;
		}

		// Convert buffer to stream to receive upload progress events
		// see https://github.com/sindresorhus/got/pull/322
		if (is.buffer(body)) {
			opts.body = intoStream(body);
			opts.body._buffer = body;
		}

		opts.method = (opts.method || 'POST').toUpperCase();
	}

	if (opts.hostname === 'unix') {
		const matches = /(.+?):(.+)/.exec(opts.path);

		if (matches) {
			opts.socketPath = matches[1];
			opts.path = matches[2];
			opts.host = null;
		}
	}

test('reuses a TLS session', wrapper, async (t, server) => {
		const agent = new Agent();
		const session = await agent.getSession(server.url);
		await setImmediateAsync();

		const tlsSession = agent.tlsSessionCache.get(`${Agent.normalizeAuthority(server.url)}:`).session;

		session.close();
		await pEvent(session, 'close');

		const secondSession = await agent.getSession(server.url);
		await setImmediateAsync();

		t.deepEqual(secondSession.socket.getSession(), tlsSession);
		t.true(is.buffer(tlsSession));

		agent.destroy();
	});

export default async (options: Options): Promise => {
	const {body, headers} = options;

	if (headers && 'content-length' in headers) {
		return Number(headers['content-length']);
	}

	if (!body) {
		return 0;
	}

	if (is.string(body)) {
		return Buffer.byteLength(body);
	}

	if (is.buffer(body)) {
		return body.length;
	}

	if (isFormData(body)) {
		return promisify(body.getLength.bind(body))();
	}

	if (body instanceof ReadStream) {
		const {size} = await statAsync(body.path);
		return size;
	}

	return undefined;
};

return 0;
	}

	if (is.string(body)) {
		return Buffer.byteLength(body);
	}

	if (isFormData(body)) {
		return pify(body.getLength.bind(body))();
	}

	if (body instanceof fs.ReadStream) {
		return pify(fs.stat)(body.path).then(stat => stat.size);
	}

	if (is.nodeStream(body) && is.buffer(body._buffer)) {
		return body._buffer.length;
	}

	return null;
};