|
| 1 | +use crate::stream::{Fuse, IntoStream, StreamExt}; |
| 2 | + |
| 3 | +use alloc::vec::Vec; |
| 4 | +use core::fmt; |
| 5 | +use core::pin::Pin; |
| 6 | +use futures_core::stream::{FusedStream, Stream, TryStream}; |
| 7 | +use futures_core::task::{Context, Poll}; |
| 8 | +#[cfg(feature = "sink")] |
| 9 | +use futures_sink::Sink; |
| 10 | +use pin_project_lite::pin_project; |
| 11 | + |
| 12 | +pin_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 | + |
| 23 | +impl<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 | + |
| 33 | +type TryReadyChunksStreamError<St> = |
| 34 | + TryReadyChunksError<<St as TryStream>::Ok, <St as TryStream>::Error>; |
| 35 | + |
| 36 | +impl<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 | + |
| 90 | +impl<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")] |
| 98 | +impl<S, Item> Sink<Item> for TryReadyChunks<S> |
| 99 | +where |
| 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)] |
| 111 | +pub struct TryReadyChunksError<T, E>(pub Vec<T>, pub E); |
| 112 | + |
| 113 | +impl<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 | + |
| 119 | +impl<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")] |
| 126 | +impl<T, E: fmt::Debug + fmt::Display> std::error::Error for TryReadyChunksError<T, E> {} |
0 commit comments