radvisor 1.3.1

Resource utilization monitor for Docker containers & Kubernetes pods that operates with fine granularity and low overhead.
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use std::cmp::Ord;
use std::collections::BTreeSet;
use std::iter::IntoIterator;

/// Utility structure for tracking a pool of items and generating events when
/// new items are added or old items are removed.
#[derive(Debug, Clone)]
pub struct ItemPool<T: Ord + Clone> {
    items:       BTreeSet<T>,
    working_set: BTreeSet<T>,
}

impl<T: Ord + Clone> Default for ItemPool<T> {
    fn default() -> Self { Self::new() }
}

impl<T: Ord + Clone> ItemPool<T> {
    #[must_use]
    pub fn new() -> Self {
        Self {
            items:       BTreeSet::new(),
            working_set: BTreeSet::new(),
        }
    }

    /// Updates the internal pool map, returning two vectors of items `(added,
    /// removed)` that represent all new items that were added (items that
    /// appear in the given iterator and not in the previous internal pool)
    /// and all old items that were removed (items that appear in the
    /// previous internal pool but not in the given iterator)
    pub fn update<I>(&mut self, new_target_ids: I) -> (Vec<T>, Vec<T>)
    where
        I: IntoIterator<Item = T>,
    {
        let items = &mut self.items;
        let working_set = &mut self.working_set;

        // Add all new target Ids to the working set
        working_set.extend(new_target_ids);

        // Note: this uses more clones than needed
        // because `BTreeSet::drain_iter` is not yet stabilized
        // https://github.com/rust-lang/rust/issues/70530
        let added = working_set.difference(items).cloned().collect::<Vec<_>>();
        let removed = items.difference(working_set).cloned().collect::<Vec<_>>();

        // Remove all items from the set
        for item in &removed {
            items.remove(item);
        }

        items.extend(added.iter().cloned());
        working_set.clear();
        (added, removed)
    }
}