+} // namespace
+
+unsigned BMUSBCapture::num_cards()
+{
+ int rc = libusb_init(nullptr);
+ if (rc < 0) {
+ fprintf(stderr, "Error initializing libusb: %s\n", libusb_error_name(rc));
+ exit(1);
+ }
+
+ vector<USBCardDevice> found_cards = find_all_cards();
+ unsigned ret = found_cards.size();
+ for (size_t i = 0; i < found_cards.size(); ++i) {
+ libusb_unref_device(found_cards[i].device);
+ }
+ return ret;
+}
+