Revision control
Copy as Markdown
Other Tools
use crate::stream::{Fuse, IntoStream, StreamExt};
use alloc::vec::Vec;
use core::pin::Pin;
use core::{fmt, mem};
use futures_core::ready;
use futures_core::stream::{FusedStream, Stream, TryStream};
use futures_core::task::{Context, Poll};
#[cfg(feature = "sink")]
use futures_sink::Sink;
use pin_project_lite::pin_project;
pin_project! {
/// Stream for the [`try_chunks`](super::TryStreamExt::try_chunks) method.
#[derive(Debug)]
#[must_use = "streams do nothing unless polled"]
pub struct TryChunks<St: TryStream> {
#[pin]
stream: Fuse<IntoStream<St>>,
items: Vec<St::Ok>,
}
}
impl<St: TryStream> TryChunks<St> {
pub(super) fn new(stream: St, capacity: usize) -> Self {
assert!(capacity > 0);
Self {
stream: IntoStream::new(stream).fuse(),
items: Vec::with_capacity(capacity),
cap: capacity,
}
}
fn take(self: Pin<&mut Self>) -> Vec<St::Ok> {
let cap = self.cap;
mem::replace(self.project().items, Vec::with_capacity(cap))
}
delegate_access_inner!(stream, St, (. .));
}
type TryChunksStreamError<St> = TryChunksError<<St as TryStream>::Ok, <St as TryStream>::Error>;
impl<St: TryStream> Stream for TryChunks<St> {
type Item = Result<Vec<St::Ok>, TryChunksStreamError<St>>;
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().try_poll_next(cx)) {
// Push the item into the buffer and check whether it is full.
// If so, replace our buffer with a new and empty one and return
// the full one.
Some(item) => match item {
Ok(item) => {
this.items.push(item);
if this.items.len() >= *this.cap {
return Poll::Ready(Some(Ok(self.take())));
}
}
Err(e) => {
return Poll::Ready(Some(Err(TryChunksError(self.take(), e))));
}
},
// Since the underlying stream ran out of values, return what we
// have buffered, if we have anything.
None => {
let last = if this.items.is_empty() {
None
} else {
let full_buf = mem::take(this.items);
Some(full_buf)
};
return Poll::Ready(last.map(Ok));
}
}
}
}
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: TryStream + FusedStream> FusedStream for TryChunks<St> {
fn is_terminated(&self) -> bool {
self.stream.is_terminated() && self.items.is_empty()
}
}
// Forwarding impl of Sink from the underlying stream
#[cfg(feature = "sink")]
impl<S, Item> Sink<Item> for TryChunks<S>
where
S: TryStream + Sink<Item>,
{
type Error = <S as Sink<Item>>::Error;
delegate_sink!(stream, Item);
}
/// Error indicating, that while chunk was collected inner stream produced an error.
///
/// Contains all items that were collected before an error occurred, and the stream error itself.
#[derive(PartialEq, Eq)]
pub struct TryChunksError<T, E>(pub Vec<T>, pub E);
impl<T, E: fmt::Debug> fmt::Debug for TryChunksError<T, E> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.1.fmt(f)
}
}
impl<T, E: fmt::Display> fmt::Display for TryChunksError<T, E> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.1.fmt(f)
}
}
#[cfg(feature = "std")]
impl<T, E: fmt::Debug + fmt::Display> std::error::Error for TryChunksError<T, E> {}