use crate::stream::Fuse;
use alloc::vec::Vec;
use core::mem;
use core::pin::Pin;
use futures_core::ready;
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 Chunks<St: Stream> {
#[pin]
stream: Fuse<St>,
items: Vec<St::Item>,
cap: usize, }
}
impl<St: Stream> Chunks<St> {
pub(super) fn new(stream: St, capacity: usize) -> Self {
assert!(capacity > 0);
Self {
stream: super::Fuse::new(stream),
items: Vec::with_capacity(capacity),
cap: capacity,
}
}
fn take(self: Pin<&mut Self>) -> Vec<St::Item> {
let cap = self.cap;
mem::replace(self.project().items, Vec::with_capacity(cap))
}
delegate_access_inner!(stream, St, (.));
}
impl<St: Stream> Stream for Chunks<St> {
type Item = Vec<St::Item>;
fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
let mut this = self.as_mut().project();
loop {
match ready!(this.stream.as_mut().poll_next(cx)) {
Some(item) => {
this.items.push(item);
if this.items.len() >= *this.cap {
return Poll::Ready(Some(self.take()));
}
}
None => {
let last = if this.items.is_empty() {
None
} else {
let full_buf = mem::take(this.items);
Some(full_buf)
};
return Poll::Ready(last);
}
}
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let chunk_len = usize::from(!self.items.is_empty());
let (lower, upper) = self.stream.size_hint();
let lower = (lower / self.cap).saturating_add(chunk_len);
let upper = match upper {
Some(x) => x.checked_add(chunk_len),
None => None,
};
(lower, upper)
}
}
impl<St: FusedStream> FusedStream for Chunks<St> {
fn is_terminated(&self) -> bool {
self.stream.is_terminated() && self.items.is_empty()
}
}
#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for Chunks<S>
where
S: Stream + Sink<Item>,
{
type Error = S::Error;
delegate_sink!(stream, Item);
}