Config Tracking for DNS

config_tracker.rs

const CONFIG_TRACKER_SIZE: usize = 500;

struct ConfigTracker {
    tx_id_set: std::collections::HashSet<u16>,
    tx_id_list: std::collections::VecDeque<u16>,
}

impl Default for ConfigTracker {
    fn default() -> Self {
        Self {
            tx_id_set: std::collections::HashSet::with_capacity(CONFIG_TRACKER_SIZE),
            tx_id_list: std::collections::VecDeque::with_capacity(CONFIG_TRACKER_SIZE),
        }
    }
}

impl ConfigTracker {
    fn with_capacity(capacity: usize) -> ConfigTracker {
        ConfigTracker {
            tx_id_set: std::collections::HashSet::with_capacity(capacity),
            tx_id_list: std::collections::VecDeque::with_capacity(capacity),
        }
    }

    fn add(&mut self, tx_id: u16) {
        if self.tx_id_list.len() == self.tx_id_list.capacity() {
            let old_tx_id = self.tx_id_list.pop_front().unwrap();
            self.tx_id_set.remove(&old_tx_id);
        }
        self.tx_id_list.push_back(tx_id);
        self.tx_id_set.insert(tx_id);
    }

    fn contains(&self, tx_id: u16) -> bool {
        self.tx_id_set.contains(&tx_id)
    }
}

#[cfg(test)]
mod config_tracker_tests {
    use super::*;

    #[test]
    fn test_config_tracker() {
        let mut tracker = ConfigTracker::with_capacity(3);
        assert_eq!(tracker.tx_id_list.len(), 0);
        assert_eq!(tracker.tx_id_set.len(), 0);
        assert_eq!(tracker.tx_id_list.capacity(), 3);
        assert_eq!(tracker.tx_id_set.capacity(), 3);

        tracker.add(9);
        assert_eq!(tracker.tx_id_list.len(), 1);
        assert_eq!(tracker.tx_id_set.len(), 1);
        assert_eq!(tracker.tx_id_list.capacity(), 3);
        assert_eq!(tracker.tx_id_set.capacity(), 3);
        assert!(tracker.contains(9));

        tracker.add(8);
        assert_eq!(tracker.tx_id_list.len(), 2);
        assert_eq!(tracker.tx_id_set.len(), 2);
        assert_eq!(tracker.tx_id_list.capacity(), 3);
        assert_eq!(tracker.tx_id_set.capacity(), 3);
        assert!(tracker.contains(8));
        assert!(tracker.contains(9));

        tracker.add(7);
        assert_eq!(tracker.tx_id_list.len(), 3);
        assert_eq!(tracker.tx_id_set.len(), 3);
        assert_eq!(tracker.tx_id_list.capacity(), 3);
        assert_eq!(tracker.tx_id_set.capacity(), 3);
        assert!(tracker.contains(7));
        assert!(tracker.contains(8));
        assert!(tracker.contains(9));

        tracker.add(6);
        assert_eq!(tracker.tx_id_list.len(), 3);
        assert_eq!(tracker.tx_id_set.len(), 3);
        assert_eq!(tracker.tx_id_list.capacity(), 3);
        assert_eq!(tracker.tx_id_set.capacity(), 3);
        assert!(tracker.contains(6));
        assert!(tracker.contains(7));
        assert!(tracker.contains(8));
        assert!(!tracker.contains(9));

    }
}