| <!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-1.28.2/src/io/async_read.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>async_read.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/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/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><span class="kw">super</span>::ReadBuf; |
| <span class="kw">use </span>std::io; |
| <span class="kw">use </span>std::ops::DerefMut; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll}; |
| |
| <span class="doccomment">/// Reads bytes from a source. |
| /// |
| /// This trait is analogous to the [`std::io::Read`] trait, but integrates with |
| /// the asynchronous task system. In particular, the [`poll_read`] method, |
| /// unlike [`Read::read`], will automatically queue the current task for wakeup |
| /// and return if data is not yet available, rather than blocking the calling |
| /// thread. |
| /// |
| /// Specifically, this means that the `poll_read` function will return one of |
| /// the following: |
| /// |
| /// * `Poll::Ready(Ok(()))` means that data was immediately read and placed into |
| /// the output buffer. The amount of data read can be determined by the |
| /// increase in the length of the slice returned by `ReadBuf::filled`. If the |
| /// difference is 0, EOF has been reached. |
| /// |
| /// * `Poll::Pending` means that no data was read into the buffer |
| /// provided. The I/O object is not currently readable but may become readable |
| /// in the future. Most importantly, **the current future's task is scheduled |
| /// to get unparked when the object is readable**. This means that like |
| /// `Future::poll` you'll receive a notification when the I/O object is |
| /// readable again. |
| /// |
| /// * `Poll::Ready(Err(e))` for other errors are standard I/O errors coming from the |
| /// underlying object. |
| /// |
| /// This trait importantly means that the `read` method only works in the |
| /// context of a future's task. The object may panic if used outside of a task. |
| /// |
| /// Utilities for working with `AsyncRead` values are provided by |
| /// [`AsyncReadExt`]. |
| /// |
| /// [`poll_read`]: AsyncRead::poll_read |
| /// [`std::io::Read`]: std::io::Read |
| /// [`Read::read`]: std::io::Read::read |
| /// [`AsyncReadExt`]: crate::io::AsyncReadExt |
| </span><span class="kw">pub trait </span>AsyncRead { |
| <span class="doccomment">/// Attempts to read from the `AsyncRead` into `buf`. |
| /// |
| /// On success, returns `Poll::Ready(Ok(()))` and places data in the |
| /// unfilled portion of `buf`. If no data was read (`buf.filled().len()` is |
| /// unchanged), it implies that EOF has been reached. |
| /// |
| /// If no data is available for reading, the method returns `Poll::Pending` |
| /// and arranges for the current task (via `cx.waker()`) to receive a |
| /// notification when the object becomes readable or is closed. |
| </span><span class="kw">fn </span>poll_read( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>>; |
| } |
| |
| <span class="macro">macro_rules! </span>deref_async_read { |
| () => { |
| <span class="kw">fn </span>poll_read( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>> { |
| Pin::new(<span class="kw-2">&mut **</span><span class="self">self</span>).poll_read(cx, buf) |
| } |
| }; |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + AsyncRead + Unpin> AsyncRead <span class="kw">for </span>Box<T> { |
| <span class="macro">deref_async_read!</span>(); |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized + AsyncRead + Unpin> AsyncRead <span class="kw">for </span><span class="kw-2">&mut </span>T { |
| <span class="macro">deref_async_read!</span>(); |
| } |
| |
| <span class="kw">impl</span><P> AsyncRead <span class="kw">for </span>Pin<P> |
| <span class="kw">where |
| </span>P: DerefMut + Unpin, |
| P::Target: AsyncRead, |
| { |
| <span class="kw">fn </span>poll_read( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>> { |
| <span class="self">self</span>.get_mut().as_mut().poll_read(cx, buf) |
| } |
| } |
| |
| <span class="kw">impl </span>AsyncRead <span class="kw">for </span><span class="kw-2">&</span>[u8] { |
| <span class="kw">fn </span>poll_read( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>> { |
| <span class="kw">let </span>amt = std::cmp::min(<span class="self">self</span>.len(), buf.remaining()); |
| <span class="kw">let </span>(a, b) = <span class="self">self</span>.split_at(amt); |
| buf.put_slice(a); |
| <span class="kw-2">*</span><span class="self">self </span>= b; |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| |
| <span class="kw">impl</span><T: AsRef<[u8]> + Unpin> AsyncRead <span class="kw">for </span>io::Cursor<T> { |
| <span class="kw">fn </span>poll_read( |
| <span class="kw-2">mut </span><span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<io::Result<()>> { |
| <span class="kw">let </span>pos = <span class="self">self</span>.position(); |
| <span class="kw">let </span>slice: <span class="kw-2">&</span>[u8] = (<span class="kw-2">*</span><span class="self">self</span>).get_ref().as_ref(); |
| |
| <span class="comment">// The position could technically be out of bounds, so don't panic... |
| </span><span class="kw">if </span>pos > slice.len() <span class="kw">as </span>u64 { |
| <span class="kw">return </span>Poll::Ready(<span class="prelude-val">Ok</span>(())); |
| } |
| |
| <span class="kw">let </span>start = pos <span class="kw">as </span>usize; |
| <span class="kw">let </span>amt = std::cmp::min(slice.len() - start, buf.remaining()); |
| <span class="comment">// Add won't overflow because of pos check above. |
| </span><span class="kw">let </span>end = start + amt; |
| buf.put_slice(<span class="kw-2">&</span>slice[start..end]); |
| <span class="self">self</span>.set_position(end <span class="kw">as </span>u64); |
| |
| Poll::Ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
