rotate method

Implementation

Future<void> rotate() async {
  try {
    await _out?.flush();
    await _out?.close();
  } catch (_) {
    // Swallowed.
  }
  _out = null;
  _openFuture = null;

  // Delete the oldest.
  if (keep > 0) {
    final oldest = File('$path.$keep');
    if (await oldest.exists()) {
      try {
        await oldest.delete();
      } catch (_) {}
    }
    // Shift .n -> .n+1 in descending order.
    for (var i = keep - 1; i >= 1; i--) {
      final from = File('$path.$i');
      if (await from.exists()) {
        try {
          await from.rename('$path.${i + 1}');
        } catch (_) {}
      }
    }
    // Rename live file to .1.
    final live = File(path);
    if (await live.exists()) {
      try {
        await live.rename('$path.1');
      } catch (_) {}
    }
  } else {
    final live = File(path);
    if (await live.exists()) {
      try {
        await live.delete();
      } catch (_) {}
    }
  }
  _bytesWritten = 0;
}