rw_stream_sink/
lib.rs

1// Copyright 2017-2020 Parity Technologies (UK) Ltd.
2//
3// Permission is hereby granted, free of charge, to any person obtaining a
4// copy of this software and associated documentation files (the "Software"),
5// to deal in the Software without restriction, including without limitation
6// the rights to use, copy, modify, merge, publish, distribute, sublicense,
7// and/or sell copies of the Software, and to permit persons to whom the
8// Software is furnished to do so, subject to the following conditions:
9//
10// The above copyright notice and this permission notice shall be included in
11// all copies or substantial portions of the Software.
12//
13// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
14// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
18// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
19// DEALINGS IN THE SOFTWARE.
20
21//! This crate provides the [`RwStreamSink`] type. It wraps around a [`Stream`]
22//! and [`Sink`] that produces and accepts byte arrays, and implements
23//! [`AsyncRead`] and [`AsyncWrite`].
24//!
25//! Each call to [`AsyncWrite::poll_write`] will send one packet to the sink.
26//! Calls to [`AsyncRead::poll_read`] will read from the stream's incoming packets.
27
28#![cfg_attr(docsrs, feature(doc_cfg, doc_auto_cfg))]
29
30use futures::{prelude::*, ready};
31use std::{
32    io::{self, Read},
33    mem,
34    pin::Pin,
35    task::{Context, Poll},
36};
37
38static_assertions::const_assert!(mem::size_of::<usize>() <= mem::size_of::<u64>());
39
40/// Wraps a [`Stream`] and [`Sink`] whose items are buffers.
41/// Implements [`AsyncRead`] and [`AsyncWrite`].
42#[pin_project::pin_project]
43pub struct RwStreamSink<S: TryStream> {
44    #[pin]
45    inner: S,
46    current_item: Option<std::io::Cursor<<S as TryStream>::Ok>>,
47}
48
49impl<S: TryStream> RwStreamSink<S> {
50    /// Wraps around `inner`.
51    pub fn new(inner: S) -> Self {
52        RwStreamSink {
53            inner,
54            current_item: None,
55        }
56    }
57}
58
59impl<S> AsyncRead for RwStreamSink<S>
60where
61    S: TryStream<Error = io::Error>,
62    <S as TryStream>::Ok: AsRef<[u8]>,
63{
64    fn poll_read(
65        self: Pin<&mut Self>,
66        cx: &mut Context,
67        buf: &mut [u8],
68    ) -> Poll<io::Result<usize>> {
69        let mut this = self.project();
70
71        // Grab the item to copy from.
72        let item_to_copy = loop {
73            if let Some(ref mut i) = this.current_item {
74                if i.position() < i.get_ref().as_ref().len() as u64 {
75                    break i;
76                }
77            }
78            *this.current_item = Some(match ready!(this.inner.as_mut().try_poll_next(cx)) {
79                Some(Ok(i)) => std::io::Cursor::new(i),
80                Some(Err(e)) => return Poll::Ready(Err(e)),
81                None => return Poll::Ready(Ok(0)), // EOF
82            });
83        };
84
85        // Copy it!
86        Poll::Ready(Ok(item_to_copy.read(buf)?))
87    }
88}
89
90impl<S> AsyncWrite for RwStreamSink<S>
91where
92    S: TryStream + Sink<<S as TryStream>::Ok, Error = io::Error>,
93    <S as TryStream>::Ok: for<'r> From<&'r [u8]>,
94{
95    fn poll_write(self: Pin<&mut Self>, cx: &mut Context, buf: &[u8]) -> Poll<io::Result<usize>> {
96        let mut this = self.project();
97        ready!(this.inner.as_mut().poll_ready(cx)?);
98        let n = buf.len();
99        if let Err(e) = this.inner.start_send(buf.into()) {
100            return Poll::Ready(Err(e));
101        }
102        Poll::Ready(Ok(n))
103    }
104
105    fn poll_flush(self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
106        let this = self.project();
107        this.inner.poll_flush(cx)
108    }
109
110    fn poll_close(self: Pin<&mut Self>, cx: &mut Context) -> Poll<io::Result<()>> {
111        let this = self.project();
112        this.inner.poll_close(cx)
113    }
114}
115
116#[cfg(test)]
117mod tests {
118    use super::RwStreamSink;
119    use async_std::task;
120    use futures::{channel::mpsc, prelude::*, stream};
121    use std::{
122        pin::Pin,
123        task::{Context, Poll},
124    };
125
126    // This struct merges a stream and a sink and is quite useful for tests.
127    struct Wrapper<St, Si>(St, Si);
128
129    impl<St, Si> Stream for Wrapper<St, Si>
130    where
131        St: Stream + Unpin,
132        Si: Unpin,
133    {
134        type Item = St::Item;
135
136        fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
137            self.0.poll_next_unpin(cx)
138        }
139    }
140
141    impl<St, Si, T> Sink<T> for Wrapper<St, Si>
142    where
143        St: Unpin,
144        Si: Sink<T> + Unpin,
145    {
146        type Error = Si::Error;
147
148        fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
149            Pin::new(&mut self.1).poll_ready(cx)
150        }
151
152        fn start_send(mut self: Pin<&mut Self>, item: T) -> Result<(), Self::Error> {
153            Pin::new(&mut self.1).start_send(item)
154        }
155
156        fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
157            Pin::new(&mut self.1).poll_flush(cx)
158        }
159
160        fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
161            Pin::new(&mut self.1).poll_close(cx)
162        }
163    }
164
165    #[test]
166    fn basic_reading() {
167        let (tx1, _) = mpsc::channel::<Vec<u8>>(10);
168        let (mut tx2, rx2) = mpsc::channel(10);
169
170        let mut wrapper = RwStreamSink::new(Wrapper(rx2.map(Ok), tx1));
171
172        task::block_on(async move {
173            tx2.send(Vec::from("hel")).await.unwrap();
174            tx2.send(Vec::from("lo wor")).await.unwrap();
175            tx2.send(Vec::from("ld")).await.unwrap();
176            tx2.close().await.unwrap();
177
178            let mut data = Vec::new();
179            wrapper.read_to_end(&mut data).await.unwrap();
180            assert_eq!(data, b"hello world");
181        })
182    }
183
184    #[test]
185    fn skip_empty_stream_items() {
186        let data: Vec<&[u8]> = vec![b"", b"foo", b"", b"bar", b"", b"baz", b""];
187        let mut rws = RwStreamSink::new(stream::iter(data).map(Ok));
188        let mut buf = [0; 9];
189        task::block_on(async move {
190            assert_eq!(3, rws.read(&mut buf).await.unwrap());
191            assert_eq!(3, rws.read(&mut buf[3..]).await.unwrap());
192            assert_eq!(3, rws.read(&mut buf[6..]).await.unwrap());
193            assert_eq!(0, rws.read(&mut buf).await.unwrap());
194            assert_eq!(b"foobarbaz", &buf[..])
195        })
196    }
197
198    #[test]
199    fn partial_read() {
200        let data: Vec<&[u8]> = vec![b"hell", b"o world"];
201        let mut rws = RwStreamSink::new(stream::iter(data).map(Ok));
202        let mut buf = [0; 3];
203        task::block_on(async move {
204            assert_eq!(3, rws.read(&mut buf).await.unwrap());
205            assert_eq!(b"hel", &buf[..3]);
206            assert_eq!(0, rws.read(&mut buf[..0]).await.unwrap());
207            assert_eq!(1, rws.read(&mut buf).await.unwrap());
208            assert_eq!(b"l", &buf[..1]);
209            assert_eq!(3, rws.read(&mut buf).await.unwrap());
210            assert_eq!(b"o w", &buf[..3]);
211            assert_eq!(0, rws.read(&mut buf[..0]).await.unwrap());
212            assert_eq!(3, rws.read(&mut buf).await.unwrap());
213            assert_eq!(b"orl", &buf[..3]);
214            assert_eq!(1, rws.read(&mut buf).await.unwrap());
215            assert_eq!(b"d", &buf[..1]);
216            assert_eq!(0, rws.read(&mut buf).await.unwrap());
217        })
218    }
219}
rw_stream_sink/lib.rs

rw_stream_sink/
lib.rs
