use crate::stream::{Fuse, StreamExt};
use alloc::vec::Vec;
use core::pin::Pin;
use futures_core::stream::{FusedStream, Stream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_project_lite::pin_project;
pin_project! {
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct ReadyChunks<St: Stream> {
#[pin]
stream: Fuse<St>,
cap: usize, }
}
impl<St: Stream> ReadyChunks<St> {
pub(super) fn new(stream: St, capacity: usize) -> Self {
assert!(capacity > 0);
Self { stream: stream.fuse(), cap: capacity }
}
delegate_access_inner!(stream, St, (.));
}
impl<St: Stream> Stream for ReadyChunks<St> {
type Item = Vec<St::Item>;
fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
let mut this = self.project();
let mut items: Vec<St::Item> = Vec::new();
loop {
match this.stream.as_mut().poll_next(cx) {
Poll::Pending => {
return if items.is_empty() { Poll::Pending } else { Poll::Ready(Some(items)) }
}
Poll::Ready(Some(item)) => {
if items.is_empty() {
items.reserve(*this.cap);
}
items.push(item);
if items.len() >= *this.cap {
return Poll::Ready(Some(items));
}
}
Poll::Ready(None) => {
let last = if items.is_empty() { None } else { Some(items) };
return Poll::Ready(last);
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (lower, upper) = self.stream.size_hint();
let lower = lower / self.cap;
(lower, upper)
}
}
impl<St: Stream> FusedStream for ReadyChunks<St> {
fn is_terminated(&self) -> bool {
self.stream.is_terminated()
}
}
#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for ReadyChunks<S>
where
S: Stream + Sink<Item>,
{
type Error = S::Error;
delegate_sink!(stream, Item);
}