1use crate::stream::{Fuse, StreamExt};
2use alloc::vec::Vec;
3use core::pin::Pin;
4use futures_core::stream::{FusedStream, Stream};
5use futures_core::task::{Context, Poll};
6#[cfg(feature = "sink")]
7use futures_sink::Sink;
8use pin_project_lite::pin_project;
9
10pin_project! {
11 /// Stream for the [`ready_chunks`](super::StreamExt::ready_chunks) method.
12 #[derive(Debug)]
13 #[must_use = "streams do nothing unless polled"]
14 pub struct ReadyChunks<St: Stream> {
15 #[pin]
16 stream: Fuse<St>,
17 cap: usize, // https://github.com/rust-lang/futures-rs/issues/1475
18 }
19}
20
21impl<St: Stream> ReadyChunks<St> {
22 pub(super) fn new(stream: St, capacity: usize) -> Self {
23 assert!(capacity > 0);
24
25 Self { stream: stream.fuse(), cap: capacity }
26 }
27
28 delegate_access_inner!(stream, St, (.));
29}
30
31impl<St: Stream> Stream for ReadyChunks<St> {
32 type Item = Vec<St::Item>;
33
34 fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
35 let mut this = self.project();
36
37 let mut items: Vec<St::Item> = Vec::new();
38
39 loop {
40 match this.stream.as_mut().poll_next(cx) {
41 // Flush all collected data if underlying stream doesn't contain
42 // more ready values
43 Poll::Pending => {
44 return if items.is_empty() { Poll::Pending } else { Poll::Ready(Some(items)) }
45 }
46
47 // Push the ready item into the buffer and check whether it is full.
48 // If so, replace our buffer with a new and empty one and return
49 // the full one.
50 Poll::Ready(Some(item)) => {
51 if items.is_empty() {
52 items.reserve(*this.cap);
53 }
54 items.push(item);
55 if items.len() >= *this.cap {
56 return Poll::Ready(Some(items));
57 }
58 }
59
60 // Since the underlying stream ran out of values, return what we
61 // have buffered, if we have anything.
62 Poll::Ready(None) => {
63 let last = if items.is_empty() { None } else { Some(items) };
64
65 return Poll::Ready(last);
66 }
67 }
68 }
69 }
70
71 fn size_hint(&self) -> (usize, Option<usize>) {
72 let (lower, upper) = self.stream.size_hint();
73 let lower = lower / self.cap;
74 (lower, upper)
75 }
76}
77
78impl<St: Stream> FusedStream for ReadyChunks<St> {
79 fn is_terminated(&self) -> bool {
80 self.stream.is_terminated()
81 }
82}
83
84// Forwarding impl of Sink from the underlying stream
85#[cfg(feature = "sink")]
86impl<S, Item> Sink<Item> for ReadyChunks<S>
87where
88 S: Stream + Sink<Item>,
89{
90 type Error = S::Error;
91
92 delegate_sink!(stream, Item);
93}
94