bundleNameForPage method
Returns the bundle name containing the given page number (1-based).
Implementation
String bundleNameForPage(int pageNumber) {
final bundleStart = ((pageNumber - 1) ~/ _bundleSize) * _bundleSize + 1;
final bundleEnd = (bundleStart + _bundleSize - 1).clamp(1, _totalPages);
return 'qfc4_pages_${bundleStart.toString().padLeft(3, '0')}_${bundleEnd.toString().padLeft(3, '0')}.zip';
}