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Manually track capacity of groups #177

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Apr 12, 2024
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Manually track capacity of groups #177

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75 changes: 58 additions & 17 deletions src/future/future_group.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,14 +67,15 @@ pub struct FutureGroup<F> {
wakers: WakerVec,
states: PollVec,
keys: BTreeSet<usize>,
capacity: usize,
}

impl<T: Debug> Debug for FutureGroup<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FutureGroup")
.field("slab", &"[..]")
.field("len", &self.futures.len())
.field("capacity", &self.futures.capacity())
.field("len", &self.len())
.field("capacity", &self.capacity)
.finish()
}
}
Expand Down Expand Up @@ -110,6 +111,7 @@ impl<F> FutureGroup<F> {
wakers: WakerVec::new(capacity),
states: PollVec::new(capacity),
keys: BTreeSet::new(),
capacity,
}
}

Expand All @@ -127,6 +129,7 @@ impl<F> FutureGroup<F> {
/// group.insert(future::ready(12));
/// assert_eq!(group.len(), 1);
/// ```
#[inline(always)]
pub fn len(&self) -> usize {
self.futures.len()
}
Expand All @@ -144,7 +147,7 @@ impl<F> FutureGroup<F> {
/// # let group: FutureGroup<usize> = group;
/// ```
pub fn capacity(&self) -> usize {
self.futures.capacity()
self.capacity
}

/// Returns true if there are no futures currently active in the group.
Expand Down Expand Up @@ -209,6 +212,36 @@ impl<F> FutureGroup<F> {
pub fn contains_key(&mut self, key: Key) -> bool {
self.keys.contains(&key.0)
}

/// Reserves capacity for `additional` more futures to be inserted.
/// Does nothing if the capacity is already sufficient.
///
/// # Example
///
/// ```rust
/// use futures_concurrency::future::FutureGroup;
/// use std::future::Ready;
/// # futures_lite::future::block_on(async {
/// let mut group: FutureGroup<Ready<usize>> = FutureGroup::with_capacity(0);
/// assert_eq!(group.capacity(), 0);
/// group.reserve(10);
/// assert_eq!(group.capacity(), 10);
///
/// // does nothing if capacity is sufficient
/// group.reserve(5);
/// assert_eq!(group.capacity(), 10);
/// # })
/// ```
pub fn reserve(&mut self, additional: usize) {
if self.len() + additional < self.capacity {
return;
}
let new_cap = self.capacity + additional;
self.wakers.resize(new_cap);
self.states.resize(new_cap);
self.futures.reserve_exact(additional);
self.capacity = new_cap;
}
}

impl<F: Future> FutureGroup<F> {
Expand All @@ -223,26 +256,22 @@ impl<F: Future> FutureGroup<F> {
/// let mut group = FutureGroup::with_capacity(2);
/// group.insert(future::ready(12));
/// ```
pub fn insert(&mut self, stream: F) -> Key
pub fn insert(&mut self, future: F) -> Key
where
F: Future,
{
let index = self.futures.insert(stream);
self.keys.insert(index);
let key = Key(index);
if self.capacity <= self.len() {
self.reserve(self.capacity * 2 + 1);
}

// If our slab allocated more space we need to
// update our tracking structures along with it.
let max_len = self.capacity().max(index);
self.wakers.resize(max_len);
self.states.resize(max_len);
let index = self.futures.insert(future);
self.keys.insert(index);

// Set the corresponding state
self.states[index].set_pending();
let mut readiness = self.wakers.readiness();
readiness.set_ready(index);
self.wakers.readiness().set_ready(index);

key
Key(index)
}

/// Insert a value into a pinned `FutureGroup`
Expand All @@ -251,14 +280,14 @@ impl<F: Future> FutureGroup<F> {
/// `ConcurrentStream`. We should never expose this publicly, as the entire
/// point of this crate is that we abstract the futures poll machinery away
/// from end-users.
pub(crate) fn insert_pinned(self: Pin<&mut Self>, stream: F) -> Key
pub(crate) fn insert_pinned(self: Pin<&mut Self>, future: F) -> Key
where
F: Future,
{
let mut this = self.project();
// SAFETY: inserting a value into the futures slab does not ever move
// any of the existing values.
let index = unsafe { this.futures.as_mut().get_unchecked_mut() }.insert(stream);
let index = unsafe { this.futures.as_mut().get_unchecked_mut() }.insert(future);
this.keys.insert(index);
let key = Key(index);

Expand Down Expand Up @@ -455,4 +484,16 @@ mod test {
assert!(group.is_empty());
});
}

#[test]
fn capacity_grow_on_insert() {
futures_lite::future::block_on(async {
let mut group = FutureGroup::new();
let cap = group.capacity();

group.insert(future::ready(1));

assert!(group.capacity() > cap);
});
}
}
68 changes: 55 additions & 13 deletions src/stream/stream_group.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ pub struct StreamGroup<S> {
states: PollVec,
keys: BTreeSet<usize>,
key_removal_queue: SmallVec<[usize; 10]>,
capacity: usize,
}

impl<T: Debug> Debug for StreamGroup<T> {
Expand Down Expand Up @@ -108,6 +109,7 @@ impl<S> StreamGroup<S> {
states: PollVec::new(capacity),
keys: BTreeSet::new(),
key_removal_queue: smallvec![],
capacity,
}
}

Expand All @@ -124,6 +126,7 @@ impl<S> StreamGroup<S> {
/// group.insert(stream::once(12));
/// assert_eq!(group.len(), 1);
/// ```
#[inline(always)]
pub fn len(&self) -> usize {
self.streams.len()
}
Expand All @@ -141,7 +144,7 @@ impl<S> StreamGroup<S> {
/// # let group: StreamGroup<usize> = group;
/// ```
pub fn capacity(&self) -> usize {
self.streams.capacity()
self.capacity
}

/// Returns true if there are no futures currently active in the group.
Expand All @@ -157,6 +160,7 @@ impl<S> StreamGroup<S> {
/// group.insert(stream::once(12));
/// assert!(!group.is_empty());
/// ```
#[inline(always)]
pub fn is_empty(&self) -> bool {
self.streams.is_empty()
}
Expand Down Expand Up @@ -206,6 +210,36 @@ impl<S> StreamGroup<S> {
pub fn contains_key(&mut self, key: Key) -> bool {
self.keys.contains(&key.0)
}

/// Reserves capacity for `additional` more streams to be inserted.
/// Does nothing if the capacity is already sufficient.
///
/// # Example
///
/// ```rust
/// use futures_concurrency::stream::StreamGroup;
/// use futures_lite::stream::Once;
/// # futures_lite::future::block_on(async {
/// let mut group: StreamGroup<Once<usize>> = StreamGroup::with_capacity(0);
/// assert_eq!(group.capacity(), 0);
/// group.reserve(10);
/// assert_eq!(group.capacity(), 10);
///
/// // does nothing if capacity is sufficient
/// group.reserve(5);
/// assert_eq!(group.capacity(), 10);
/// # })
/// ```
pub fn reserve(&mut self, additional: usize) {
if self.len() + additional < self.capacity {
return;
}
let new_cap = self.capacity + additional;
self.wakers.resize(new_cap);
self.states.resize(new_cap);
self.streams.reserve_exact(additional);
self.capacity = new_cap;
}
}

impl<S: Stream> StreamGroup<S> {
Expand All @@ -224,22 +258,18 @@ impl<S: Stream> StreamGroup<S> {
where
S: Stream,
{
if self.capacity <= self.len() {
self.reserve(self.capacity * 2 + 1);
}

let index = self.streams.insert(stream);
self.keys.insert(index);
let key = Key(index);

// If our slab allocated more space we need to
// update our tracking structures along with it.
let max_len = self.capacity().max(index);
self.wakers.resize(max_len);
self.states.resize(max_len);

// Set the corresponding state
self.states[index].set_pending();
let mut readiness = self.wakers.readiness();
readiness.set_ready(index);
self.wakers.readiness().set_ready(index);

key
Key(index)
}

/// Create a stream which also yields the key of each item.
Expand Down Expand Up @@ -270,10 +300,10 @@ impl<S: Stream> StreamGroup<S> {

impl<S: Stream> StreamGroup<S> {
fn poll_next_inner(
self: Pin<&mut Self>,
mut self: Pin<&mut Self>,
cx: &Context<'_>,
) -> Poll<Option<(Key, <S as Stream>::Item)>> {
let mut this = self.project();
let mut this = self.as_mut().project();

// Short-circuit if we have no streams to iterate over
if this.streams.is_empty() {
Expand Down Expand Up @@ -441,4 +471,16 @@ mod test {
assert!(group.is_empty());
});
}

#[test]
fn capacity_grow_on_insert() {
futures_lite::future::block_on(async {
let mut group = StreamGroup::new();
let cap = group.capacity();

group.insert(stream::once(1));

assert!(group.capacity() > cap);
});
}
}
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