func runInGvisor()

in sandbox/sandbox.go [323:368]
42 lines of code
10 McCabe index (conditional complexity)

func runInGvisor() {
	const binPath = "/tmpfs/play"
	if _, err := io.WriteString(os.Stdout, containedStartMessage); err != nil {
		log.Fatalf("writing to stdout: %v", err)
	}
	slurp, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		log.Fatalf("reading stdin in contained mode: %v", err)
	}
	nl := bytes.IndexByte(slurp, '\n')
	if nl == -1 {
		log.Fatalf("no newline found in input")
	}
	metaJSON, bin := slurp[:nl], slurp[nl+1:]

	if err := ioutil.WriteFile(binPath, bin, 0755); err != nil {
		log.Fatalf("writing contained binary: %v", err)
	}
	defer os.Remove(binPath) // not that it matters much, this container will be nuked

	var meta processMeta
	if err := json.NewDecoder(bytes.NewReader(metaJSON)).Decode(&meta); err != nil {
		log.Fatalf("error decoding JSON meta: %v", err)
	}

	if _, err := os.Stderr.Write(containedStderrHeader); err != nil {
		log.Fatalf("writing header to stderr: %v", err)
	}

	cmd := exec.Command(binPath)
	cmd.Args = append(cmd.Args, meta.Args...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	if err := cmd.Start(); err != nil {
		log.Fatalf("cmd.Start(): %v", err)
	}
	ctx, cancel := context.WithTimeout(context.Background(), runTimeout-500*time.Millisecond)
	defer cancel()
	if err = internal.WaitOrStop(ctx, cmd, os.Interrupt, 250*time.Millisecond); err != nil {
		if errors.Is(err, context.DeadlineExceeded) {
			fmt.Fprintln(os.Stderr, "timeout running program")
		}
	}
	os.Exit(errExitCode(err))
	return
}