/
buffer.rs
137 lines (118 loc) · 3.71 KB
/
buffer.rs
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use crate::atomic::AtomicOption;
use crossbeam_queue::ArrayQueue;
use derivative::Derivative;
#[derive(Derivative)]
#[derivative(Debug(bound = ""))]
#[allow(clippy::large_enum_variant)]
pub(super) enum RingBuffer<T> {
Atomic(AtomicOption<T>),
Queue(ArrayQueue<T>),
}
impl<T> RingBuffer<T> {
pub(super) fn new(capacity: usize) -> Self {
assert!(capacity > 0, "capacity must be non-zero");
if capacity == 1 {
RingBuffer::Atomic(Default::default())
} else {
RingBuffer::Queue(ArrayQueue::new(capacity))
}
}
#[cfg(test)]
#[inline]
pub(super) fn capacity(&self) -> usize {
match self {
RingBuffer::Atomic(_) => 1,
RingBuffer::Queue(q) => q.capacity(),
}
}
#[inline]
pub(super) fn push(&self, value: T) -> Option<T> {
match self {
RingBuffer::Atomic(c) => c.swap(value),
RingBuffer::Queue(q) => q.force_push(value),
}
}
#[inline]
pub(super) fn pop(&self) -> Option<T> {
match self {
RingBuffer::Atomic(c) => c.take(),
RingBuffer::Queue(q) => q.pop(),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Void;
use alloc::{collections::BinaryHeap, sync::Arc, vec::Vec};
use core::{iter, mem::discriminant};
use futures::future::try_join_all;
use proptest::collection::size_range;
use test_strategy::proptest;
use tokio::{runtime, task::spawn_blocking};
#[should_panic]
#[proptest]
fn new_panics_if_capacity_is_zero() {
RingBuffer::<Void>::new(0);
}
#[proptest]
fn atomic_option_is_used_when_capacity_is_one() {
assert_eq!(
discriminant(&RingBuffer::<Void>::new(1)),
discriminant(&RingBuffer::Atomic(Default::default()))
);
assert_eq!(
discriminant(&RingBuffer::<Void>::new(2)),
discriminant(&RingBuffer::Queue(ArrayQueue::new(2)))
);
}
#[proptest]
fn capacity_returns_the_maximum_buffer_size(#[strategy(1..=10usize)] cap: usize) {
assert_eq!(RingBuffer::<Void>::new(cap).capacity(), cap);
}
#[proptest]
fn oldest_items_are_overwritten_on_overflow(
#[strategy(1..=10usize)] cap: usize,
#[any(size_range(#cap..=10).lift())] items: Vec<u8>,
) {
let buffer = RingBuffer::new(cap);
for &item in &items[..cap] {
assert_eq!(buffer.push(item), None);
}
for (&prev, &item) in items.iter().zip(&items[cap..]) {
assert_eq!(buffer.push(item), Some(prev));
}
assert_eq!(
iter::from_fn(|| buffer.pop()).collect::<Vec<_>>(),
items[(items.len() - cap)..]
);
}
#[proptest]
fn buffer_is_linearizable(
#[strategy(1..=10usize)] n: usize,
#[strategy(1..=10usize)] m: usize,
#[strategy(1..=10usize)] cap: usize,
) {
let rt = runtime::Builder::new_multi_thread().build()?;
let buffer = Arc::new(RingBuffer::new(cap));
let items = rt.block_on(async {
try_join_all(iter::repeat(buffer).enumerate().take(m).map(|(i, b)| {
spawn_blocking(move || {
(i * n..(i + 1) * n)
.flat_map(|j| match b.push(j) {
None => b.pop(),
item => item,
})
.collect::<Vec<_>>()
})
}))
.await
})?;
let sorted = items
.into_iter()
.flatten()
.collect::<BinaryHeap<_>>()
.into_sorted_vec();
assert_eq!(sorted, (0..m * n).collect::<Vec<_>>());
}
}