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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-util-0.7.8/src/io/stream_reader.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>stream_reader.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../tokio_util/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../tokio_util/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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</pre><pre class="rust"><code><span class="kw">use </span>bytes::Buf;
<span class="kw">use </span>futures_core::stream::Stream;
<span class="kw">use </span>std::io;
<span class="kw">use </span>std::pin::Pin;
<span class="kw">use </span>std::task::{Context, Poll};
<span class="kw">use </span>tokio::io::{AsyncBufRead, AsyncRead, ReadBuf};
<span class="doccomment">/// Convert a [`Stream`] of byte chunks into an [`AsyncRead`].
///
/// This type performs the inverse operation of [`ReaderStream`].
///
/// This type also implements the [`AsyncBufRead`] trait, so you can use it
/// to read a `Stream` of byte chunks line-by-line. See the examples below.
///
/// # Example
///
/// ```
/// use bytes::Bytes;
/// use tokio::io::{AsyncReadExt, Result};
/// use tokio_util::io::StreamReader;
/// # #[tokio::main(flavor = &quot;current_thread&quot;)]
/// # async fn main() -&gt; std::io::Result&lt;()&gt; {
///
/// // Create a stream from an iterator.
/// let stream = tokio_stream::iter(vec![
/// Result::Ok(Bytes::from_static(&amp;[0, 1, 2, 3])),
/// Result::Ok(Bytes::from_static(&amp;[4, 5, 6, 7])),
/// Result::Ok(Bytes::from_static(&amp;[8, 9, 10, 11])),
/// ]);
///
/// // Convert it to an AsyncRead.
/// let mut read = StreamReader::new(stream);
///
/// // Read five bytes from the stream.
/// let mut buf = [0; 5];
/// read.read_exact(&amp;mut buf).await?;
/// assert_eq!(buf, [0, 1, 2, 3, 4]);
///
/// // Read the rest of the current chunk.
/// assert_eq!(read.read(&amp;mut buf).await?, 3);
/// assert_eq!(&amp;buf[..3], [5, 6, 7]);
///
/// // Read the next chunk.
/// assert_eq!(read.read(&amp;mut buf).await?, 4);
/// assert_eq!(&amp;buf[..4], [8, 9, 10, 11]);
///
/// // We have now reached the end.
/// assert_eq!(read.read(&amp;mut buf).await?, 0);
///
/// # Ok(())
/// # }
/// ```
///
/// If the stream produces errors which are not [`std::io::Error`],
/// the errors can be converted using [`StreamExt`] to map each
/// element.
///
/// ```
/// use bytes::Bytes;
/// use tokio::io::AsyncReadExt;
/// use tokio_util::io::StreamReader;
/// use tokio_stream::StreamExt;
/// # #[tokio::main(flavor = &quot;current_thread&quot;)]
/// # async fn main() -&gt; std::io::Result&lt;()&gt; {
///
/// // Create a stream from an iterator, including an error.
/// let stream = tokio_stream::iter(vec![
/// Result::Ok(Bytes::from_static(&amp;[0, 1, 2, 3])),
/// Result::Ok(Bytes::from_static(&amp;[4, 5, 6, 7])),
/// Result::Err(&quot;Something bad happened!&quot;)
/// ]);
///
/// // Use StreamExt to map the stream and error to a std::io::Error
/// let stream = stream.map(|result| result.map_err(|err| {
/// std::io::Error::new(std::io::ErrorKind::Other, err)
/// }));
///
/// // Convert it to an AsyncRead.
/// let mut read = StreamReader::new(stream);
///
/// // Read five bytes from the stream.
/// let mut buf = [0; 5];
/// read.read_exact(&amp;mut buf).await?;
/// assert_eq!(buf, [0, 1, 2, 3, 4]);
///
/// // Read the rest of the current chunk.
/// assert_eq!(read.read(&amp;mut buf).await?, 3);
/// assert_eq!(&amp;buf[..3], [5, 6, 7]);
///
/// // Reading the next chunk will produce an error
/// let error = read.read(&amp;mut buf).await.unwrap_err();
/// assert_eq!(error.kind(), std::io::ErrorKind::Other);
/// assert_eq!(error.into_inner().unwrap().to_string(), &quot;Something bad happened!&quot;);
///
/// // We have now reached the end.
/// assert_eq!(read.read(&amp;mut buf).await?, 0);
///
/// # Ok(())
/// # }
/// ```
///
/// Using the [`AsyncBufRead`] impl, you can read a `Stream` of byte chunks
/// line-by-line. Note that you will usually also need to convert the error
/// type when doing this. See the second example for an explanation of how
/// to do this.
///
/// ```
/// use tokio::io::{Result, AsyncBufReadExt};
/// use tokio_util::io::StreamReader;
/// # #[tokio::main(flavor = &quot;current_thread&quot;)]
/// # async fn main() -&gt; std::io::Result&lt;()&gt; {
///
/// // Create a stream of byte chunks.
/// let stream = tokio_stream::iter(vec![
/// Result::Ok(b&quot;The first line.\n&quot;.as_slice()),
/// Result::Ok(b&quot;The second line.&quot;.as_slice()),
/// Result::Ok(b&quot;\nThe third&quot;.as_slice()),
/// Result::Ok(b&quot; line.\nThe fourth line.\nThe fifth line.\n&quot;.as_slice()),
/// ]);
///
/// // Convert it to an AsyncRead.
/// let mut read = StreamReader::new(stream);
///
/// // Loop through the lines from the `StreamReader`.
/// let mut line = String::new();
/// let mut lines = Vec::new();
/// loop {
/// line.clear();
/// let len = read.read_line(&amp;mut line).await?;
/// if len == 0 { break; }
/// lines.push(line.clone());
/// }
///
/// // Verify that we got the lines we expected.
/// assert_eq!(
/// lines,
/// vec![
/// &quot;The first line.\n&quot;,
/// &quot;The second line.\n&quot;,
/// &quot;The third line.\n&quot;,
/// &quot;The fourth line.\n&quot;,
/// &quot;The fifth line.\n&quot;,
/// ]
/// );
/// # Ok(())
/// # }
/// ```
///
/// [`AsyncRead`]: tokio::io::AsyncRead
/// [`AsyncBufRead`]: tokio::io::AsyncBufRead
/// [`Stream`]: futures_core::Stream
/// [`ReaderStream`]: crate::io::ReaderStream
/// [`StreamExt`]: https://docs.rs/tokio-stream/latest/tokio_stream/trait.StreamExt.html
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">pub struct </span>StreamReader&lt;S, B&gt; {
<span class="comment">// This field is pinned.
</span>inner: S,
<span class="comment">// This field is not pinned.
</span>chunk: <span class="prelude-ty">Option</span>&lt;B&gt;,
}
<span class="kw">impl</span>&lt;S, B, E&gt; StreamReader&lt;S, B&gt;
<span class="kw">where
</span>S: Stream&lt;Item = <span class="prelude-ty">Result</span>&lt;B, E&gt;&gt;,
B: Buf,
E: Into&lt;std::io::Error&gt;,
{
<span class="doccomment">/// Convert a stream of byte chunks into an [`AsyncRead`](tokio::io::AsyncRead).
///
/// The item should be a [`Result`] with the ok variant being something that
/// implements the [`Buf`] trait (e.g. `Vec&lt;u8&gt;` or `Bytes`). The error
/// should be convertible into an [io error].
///
/// [`Result`]: std::result::Result
/// [`Buf`]: bytes::Buf
/// [io error]: std::io::Error
</span><span class="kw">pub fn </span>new(stream: S) -&gt; <span class="self">Self </span>{
<span class="self">Self </span>{
inner: stream,
chunk: <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Do we have a chunk and is it non-empty?
</span><span class="kw">fn </span>has_chunk(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; bool {
<span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">ref </span>chunk) = <span class="self">self</span>.chunk {
chunk.remaining() &gt; <span class="number">0
</span>} <span class="kw">else </span>{
<span class="bool-val">false
</span>}
}
<span class="doccomment">/// Consumes this `StreamReader`, returning a Tuple consisting
/// of the underlying stream and an Option of the internal buffer,
/// which is Some in case the buffer contains elements.
</span><span class="kw">pub fn </span>into_inner_with_chunk(<span class="self">self</span>) -&gt; (S, <span class="prelude-ty">Option</span>&lt;B&gt;) {
<span class="kw">if </span><span class="self">self</span>.has_chunk() {
(<span class="self">self</span>.inner, <span class="self">self</span>.chunk)
} <span class="kw">else </span>{
(<span class="self">self</span>.inner, <span class="prelude-val">None</span>)
}
}
}
<span class="kw">impl</span>&lt;S, B&gt; StreamReader&lt;S, B&gt; {
<span class="doccomment">/// Gets a reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
</span><span class="kw">pub fn </span>get_ref(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; <span class="kw-2">&amp;</span>S {
<span class="kw-2">&amp;</span><span class="self">self</span>.inner
}
<span class="doccomment">/// Gets a mutable reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
</span><span class="kw">pub fn </span>get_mut(<span class="kw-2">&amp;mut </span><span class="self">self</span>) -&gt; <span class="kw-2">&amp;mut </span>S {
<span class="kw-2">&amp;mut </span><span class="self">self</span>.inner
}
<span class="doccomment">/// Gets a pinned mutable reference to the underlying stream.
///
/// It is inadvisable to directly read from the underlying stream.
</span><span class="kw">pub fn </span>get_pin_mut(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;) -&gt; Pin&lt;<span class="kw-2">&amp;mut </span>S&gt; {
<span class="self">self</span>.project().inner
}
<span class="doccomment">/// Consumes this `BufWriter`, returning the underlying stream.
///
/// Note that any leftover data in the internal buffer is lost.
/// If you additionally want access to the internal buffer use
/// [`into_inner_with_chunk`].
///
/// [`into_inner_with_chunk`]: crate::io::StreamReader::into_inner_with_chunk
</span><span class="kw">pub fn </span>into_inner(<span class="self">self</span>) -&gt; S {
<span class="self">self</span>.inner
}
}
<span class="kw">impl</span>&lt;S, B, E&gt; AsyncRead <span class="kw">for </span>StreamReader&lt;S, B&gt;
<span class="kw">where
</span>S: Stream&lt;Item = <span class="prelude-ty">Result</span>&lt;B, E&gt;&gt;,
B: Buf,
E: Into&lt;std::io::Error&gt;,
{
<span class="kw">fn </span>poll_read(
<span class="kw-2">mut </span><span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;,
cx: <span class="kw-2">&amp;mut </span>Context&lt;<span class="lifetime">&#39;_</span>&gt;,
buf: <span class="kw-2">&amp;mut </span>ReadBuf&lt;<span class="lifetime">&#39;_</span>&gt;,
) -&gt; Poll&lt;io::Result&lt;()&gt;&gt; {
<span class="kw">if </span>buf.remaining() == <span class="number">0 </span>{
<span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(()));
}
<span class="kw">let </span>inner_buf = <span class="kw">match </span><span class="self">self</span>.as_mut().poll_fill_buf(cx) {
Poll::Ready(<span class="prelude-val">Ok</span>(buf)) =&gt; buf,
Poll::Ready(<span class="prelude-val">Err</span>(err)) =&gt; <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Err</span>(err)),
Poll::Pending =&gt; <span class="kw">return </span>Poll::Pending,
};
<span class="kw">let </span>len = std::cmp::min(inner_buf.len(), buf.remaining());
buf.put_slice(<span class="kw-2">&amp;</span>inner_buf[..len]);
<span class="self">self</span>.consume(len);
Poll::Ready(<span class="prelude-val">Ok</span>(()))
}
}
<span class="kw">impl</span>&lt;S, B, E&gt; AsyncBufRead <span class="kw">for </span>StreamReader&lt;S, B&gt;
<span class="kw">where
</span>S: Stream&lt;Item = <span class="prelude-ty">Result</span>&lt;B, E&gt;&gt;,
B: Buf,
E: Into&lt;std::io::Error&gt;,
{
<span class="kw">fn </span>poll_fill_buf(<span class="kw-2">mut </span><span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;, cx: <span class="kw-2">&amp;mut </span>Context&lt;<span class="lifetime">&#39;_</span>&gt;) -&gt; Poll&lt;io::Result&lt;<span class="kw-2">&amp;</span>[u8]&gt;&gt; {
<span class="kw">loop </span>{
<span class="kw">if </span><span class="self">self</span>.as_mut().has_chunk() {
<span class="comment">// This unwrap is very sad, but it can&#39;t be avoided.
</span><span class="kw">let </span>buf = <span class="self">self</span>.project().chunk.as_ref().unwrap().chunk();
<span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(buf));
} <span class="kw">else </span>{
<span class="kw">match </span><span class="self">self</span>.as_mut().project().inner.poll_next(cx) {
Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(chunk))) =&gt; {
<span class="comment">// Go around the loop in case the chunk is empty.
</span><span class="kw-2">*</span><span class="self">self</span>.as_mut().project().chunk = <span class="prelude-val">Some</span>(chunk);
}
Poll::Ready(<span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(err))) =&gt; <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Err</span>(err.into())),
Poll::Ready(<span class="prelude-val">None</span>) =&gt; <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(<span class="kw-2">&amp;</span>[])),
Poll::Pending =&gt; <span class="kw">return </span>Poll::Pending,
}
}
}
}
<span class="kw">fn </span>consume(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;, amt: usize) {
<span class="kw">if </span>amt &gt; <span class="number">0 </span>{
<span class="self">self</span>.project()
.chunk
.as_mut()
.expect(<span class="string">&quot;No chunk present&quot;</span>)
.advance(amt);
}
}
}
<span class="comment">// The code below is a manual expansion of the code that pin-project-lite would
// generate. This is done because pin-project-lite fails by hitting the recusion
// limit on this struct. (Every line of documentation is handled recursively by
// the macro.)
</span><span class="kw">impl</span>&lt;S: Unpin, B&gt; Unpin <span class="kw">for </span>StreamReader&lt;S, B&gt; {}
<span class="kw">struct </span>StreamReaderProject&lt;<span class="lifetime">&#39;a</span>, S, B&gt; {
inner: Pin&lt;<span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span><span class="kw-2">mut </span>S&gt;,
chunk: <span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span><span class="kw-2">mut </span><span class="prelude-ty">Option</span>&lt;B&gt;,
}
<span class="kw">impl</span>&lt;S, B&gt; StreamReader&lt;S, B&gt; {
<span class="attribute">#[inline]
</span><span class="kw">fn </span>project(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;) -&gt; StreamReaderProject&lt;<span class="lifetime">&#39;_</span>, S, B&gt; {
<span class="comment">// SAFETY: We define that only `inner` should be pinned when `Self` is
// and have an appropriate `impl Unpin` for this.
</span><span class="kw">let </span>me = <span class="kw">unsafe </span>{ Pin::into_inner_unchecked(<span class="self">self</span>) };
StreamReaderProject {
inner: <span class="kw">unsafe </span>{ Pin::new_unchecked(<span class="kw-2">&amp;mut </span>me.inner) },
chunk: <span class="kw-2">&amp;mut </span>me.chunk,
}
}
}
</code></pre></div>
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