1use crate::stream::{Fuse, IntoStream, StreamExt};
2
3use alloc::vec::Vec;
4use core::fmt;
5use core::pin::Pin;
6use futures_core::stream::{FusedStream, Stream, TryStream};
7use futures_core::task::{Context, Poll};
8#[cfg(feature = "sink")]
9use futures_sink::Sink;
10use pin_project_lite::pin_project;
11
12pin_project! {
13 /// Stream for the [`try_ready_chunks`](super::TryStreamExt::try_ready_chunks) method.
14 #[derive(Debug)]
15 #[must_use = "streams do nothing unless polled"]
16 pub struct TryReadyChunks<St: TryStream> {
17 #[pin]
18 stream: Fuse<IntoStream<St>>,
19 cap: usize, // https://github.com/rust-lang/futures-rs/issues/1475
20 }
21}
22
23impl<St: TryStream> TryReadyChunks<St> {
24 pub(super) fn new(stream: St, capacity: usize) -> Self {
25 assert!(capacity > 0);
26
27 Self { stream: IntoStream::new(stream).fuse(), cap: capacity }
28 }
29
30 delegate_access_inner!(stream, St, (. .));
31}
32
33type TryReadyChunksStreamError<St> =
34 TryReadyChunksError<<St as TryStream>::Ok, <St as TryStream>::Error>;
35
36impl<St: TryStream> Stream for TryReadyChunks<St> {
37 type Item = Result<Vec<St::Ok>, TryReadyChunksStreamError<St>>;
38
39 fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
40 let mut this = self.as_mut().project();
41
42 let mut items: Vec<St::Ok> = Vec::new();
43
44 loop {
45 match this.stream.as_mut().poll_next(cx) {
46 // Flush all the collected data if the underlying stream doesn't
47 // contain more ready values
48 Poll::Pending => {
49 return if items.is_empty() {
50 Poll::Pending
51 } else {
52 Poll::Ready(Some(Ok(items)))
53 }
54 }
55
56 // Push the ready item into the buffer and check whether it is full.
57 // If so, return the buffer.
58 Poll::Ready(Some(Ok(item))) => {
59 if items.is_empty() {
60 items.reserve_exact(*this.cap);
61 }
62 items.push(item);
63 if items.len() >= *this.cap {
64 return Poll::Ready(Some(Ok(items)));
65 }
66 }
67
68 // Return the already collected items and the error.
69 Poll::Ready(Some(Err(e))) => {
70 return Poll::Ready(Some(Err(TryReadyChunksError(items, e))));
71 }
72
73 // Since the underlying stream ran out of values, return what we
74 // have buffered, if we have anything.
75 Poll::Ready(None) => {
76 let last = if items.is_empty() { None } else { Some(Ok(items)) };
77 return Poll::Ready(last);
78 }
79 }
80 }
81 }
82
83 fn size_hint(&self) -> (usize, Option<usize>) {
84 let (lower, upper) = self.stream.size_hint();
85 let lower = lower / self.cap;
86 (lower, upper)
87 }
88}
89
90impl<St: TryStream + FusedStream> FusedStream for TryReadyChunks<St> {
91 fn is_terminated(&self) -> bool {
92 self.stream.is_terminated()
93 }
94}
95
96// Forwarding impl of Sink from the underlying stream
97#[cfg(feature = "sink")]
98impl<S, Item> Sink<Item> for TryReadyChunks<S>
99where
100 S: TryStream + Sink<Item>,
101{
102 type Error = <S as Sink<Item>>::Error;
103
104 delegate_sink!(stream, Item);
105}
106
107/// Error indicating, that while chunk was collected inner stream produced an error.
108///
109/// Contains all items that were collected before an error occurred, and the stream error itself.
110#[derive(PartialEq, Eq)]
111pub struct TryReadyChunksError<T, E>(pub Vec<T>, pub E);
112
113impl<T, E: fmt::Debug> fmt::Debug for TryReadyChunksError<T, E> {
114 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
115 self.1.fmt(f)
116 }
117}
118
119impl<T, E: fmt::Display> fmt::Display for TryReadyChunksError<T, E> {
120 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
121 self.1.fmt(f)
122 }
123}
124
125#[cfg(feature = "std")]
126impl<T, E: fmt::Debug + fmt::Display> std::error::Error for TryReadyChunksError<T, E> {}
127