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// This file is part of Soil.
// Copyright (C) Soil contributors.
// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
//! `soil-network` utilities
use futures::{stream::unfold, FutureExt, Stream, StreamExt};
use futures_timer::Delay;
use linked_hash_set::LinkedHashSet;
use std::{hash::Hash, num::NonZeroUsize, time::Duration};
/// Creates a stream that returns a new value every `duration`.
pub fn interval(duration: Duration) -> impl Stream<Item = ()> + Unpin {
unfold((), move |_| Delay::new(duration).map(|_| Some(((), ())))).map(drop)
}
/// Wrapper around `LinkedHashSet` with bounded growth.
///
/// In the limit, for each element inserted the oldest existing element will be removed.
#[derive(Debug, Clone)]
pub struct LruHashSet<T: Hash + Eq> {
set: LinkedHashSet<T>,
limit: NonZeroUsize,
}
impl<T: Hash + Eq> LruHashSet<T> {
/// Create a new `LruHashSet` with the given (exclusive) limit.
pub fn new(limit: NonZeroUsize) -> Self {
Self { set: LinkedHashSet::new(), limit }
}
/// Insert element into the set.
///
/// Returns `true` if this is a new element to the set, `false` otherwise.
/// Maintains the limit of the set by removing the oldest entry if necessary.
/// Inserting the same element will update its LRU position.
pub fn insert(&mut self, e: T) -> bool {
if self.set.insert(e) {
if self.set.len() == usize::from(self.limit) {
self.set.pop_front(); // remove oldest entry
}
return true;
}
false
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn maintains_limit() {
let three = NonZeroUsize::new(3).unwrap();
let mut set = LruHashSet::<u8>::new(three);
// First element.
assert!(set.insert(1));
assert_eq!(vec![&1], set.set.iter().collect::<Vec<_>>());
// Second element.
assert!(set.insert(2));
assert_eq!(vec![&1, &2], set.set.iter().collect::<Vec<_>>());
// Inserting the same element updates its LRU position.
assert!(!set.insert(1));
assert_eq!(vec![&2, &1], set.set.iter().collect::<Vec<_>>());
// We reached the limit. The next element forces the oldest one out.
assert!(set.insert(3));
assert_eq!(vec![&1, &3], set.set.iter().collect::<Vec<_>>());
}
}