Struct StreamGroup

pub struct StreamGroup<S> { /* private fields */ }

A growable group of streams which act as a single unit.

Example

Basic example

use futures_concurrency::stream::StreamGroup;
use futures_lite::{stream, StreamExt};

let mut group = StreamGroup::new();
group.insert(stream::once(2));
group.insert(stream::once(4));

let mut out = 0;
while let Some(num) = group.next().await {
    out += num;
}
assert_eq!(out, 6);

Update the group on every iteration

use futures_concurrency::stream::StreamGroup;
use lending_stream::prelude::*;
use futures_lite::stream;

let mut group = StreamGroup::new();
group.insert(stream::once(4));

let mut index = 3;
let mut out = 0;
let mut group = group.lend_mut();
while let Some((group, num)) = group.next().await {
    if index != 0 {
        group.insert(stream::once(index));
        index -= 1;
    }
    out += num;
}
assert_eq!(out, 10);

Implementations

impl<S> StreamGroup<S>

pub fn new() -> Self

Create a new instance of StreamGroup.

Example

use futures_concurrency::stream::StreamGroup;

let group = StreamGroup::new();

pub fn with_capacity(capacity: usize) -> Self

Create a new instance of StreamGroup with a given capacity.

Example

use futures_concurrency::stream::StreamGroup;

let group = StreamGroup::with_capacity(2);

pub fn len(&self) -> usize

Return the number of futures currently active in the group.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::stream;

let mut group = StreamGroup::with_capacity(2);
assert_eq!(group.len(), 0);
group.insert(stream::once(12));
assert_eq!(group.len(), 1);

pub fn capacity(&self) -> usize

Return the capacity of the StreamGroup.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::stream;

let group = StreamGroup::with_capacity(2);
assert_eq!(group.capacity(), 2);

pub fn is_empty(&self) -> bool

Returns true if there are no futures currently active in the group.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::stream;

let mut group = StreamGroup::with_capacity(2);
assert!(group.is_empty());
group.insert(stream::once(12));
assert!(!group.is_empty());

pub fn remove(&mut self, key: Key) -> bool

Removes a stream from the group. Returns whether the value was present in the group.

Example

use futures_lite::stream;
use futures_concurrency::stream::StreamGroup;

let mut group = StreamGroup::new();
let key = group.insert(stream::once(4));
assert_eq!(group.len(), 1);
group.remove(key);
assert_eq!(group.len(), 0);

pub fn contains_key(&mut self, key: Key) -> bool

Returns true if the StreamGroup contains a value for the specified key.

Example

use futures_lite::stream;
use futures_concurrency::stream::StreamGroup;

let mut group = StreamGroup::new();
let key = group.insert(stream::once(4));
assert!(group.contains_key(key));
group.remove(key);
assert!(!group.contains_key(key));

pub fn reserve(&mut self, additional: usize)

Reserves capacity for additional more streams to be inserted. Does nothing if the capacity is already sufficient.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::stream::Once;
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);

impl<S: Stream> StreamGroup<S>

pub fn insert(&mut self, stream: S) -> Key

where S: Stream,

Insert a new future into the group.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::stream;

let mut group = StreamGroup::with_capacity(2);
group.insert(stream::once(12));

pub fn keyed(self) -> Keyed<S>

Create a stream which also yields the key of each item.

Example

use futures_concurrency::stream::StreamGroup;
use futures_lite::{stream, StreamExt};

let mut group = StreamGroup::new();
group.insert(stream::once(2));
group.insert(stream::once(4));

let mut out = 0;
let mut group = group.keyed();
while let Some((_key, num)) = group.next().await {
    out += num;
}
assert_eq!(out, 6);

Trait Implementations

impl<T: Debug> Debug for StreamGroup<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<S: Default> Default for StreamGroup<S>

fn default() -> StreamGroup<S>

Returns the “default value” for a type.

impl<S: Stream> FromIterator<S> for StreamGroup<S>

fn from_iter<T: IntoIterator<Item = S>>(iter: T) -> Self

Creates a value from an iterator.

impl<S: Stream> Stream for StreamGroup<S>

type Item = <S as Stream>::Item

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<Self::Item>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.

impl<'pin, S> Unpin for StreamGroup<S>

where __StreamGroup<'pin, S>: Unpin,