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33 lines
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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="Asynchronously copies the entire contents of a reader into a writer."><title>copy_buf in tokio::io - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Italic-81dc35de.woff2,FiraSans-Regular-0fe48ade.woff2,FiraSans-MediumItalic-ccf7e434.woff2,FiraSans-Medium-e1aa3f0a.woff2,SourceCodePro-Regular-8badfe75.ttf.woff2,SourceCodePro-Semibold-aa29a496.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2"href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../../static.files/rustdoc-ca0dd0c4.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="tokio" data-themes="" data-resource-suffix="" data-rustdoc-version="1.93.1 (01f6ddf75 2026-02-11) (Arch Linux rust 1:1.93.1-1)" data-channel="1.93.1" data-search-js="search-9e2438ea.js" data-stringdex-js="stringdex-a3946164.js" data-settings-js="settings-c38705f0.js" ><script src="../../static.files/storage-e2aeef58.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-a410ff4d.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-263c88ec.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-eab170b8.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-044be391.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><rustdoc-topbar><h2><a href="#">copy_buf</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../tokio/index.html">tokio</a><span class="version">1.49.0</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">copy_<wbr>buf</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#when-to-use-async-alternatives-instead-of-synciobridge" title="When to use async alternatives instead of `SyncIoBridge`">When to use async alternatives instead of <code>SyncIoBridge</code></a></li><li><a href="#errors" title="Errors">Errors</a></li><li><a href="#examples" title="Examples">Examples</a></li></ul></section><div id="rustdoc-modnav"><h2><a href="index.html">In tokio::<wbr>io</a></h2></div></div></nav><div class="sidebar-resizer" title="Drag to resize sidebar"></div><main><div class="width-limiter"><section id="main-content" class="content"><div class="main-heading"><div class="rustdoc-breadcrumbs"><a href="../index.html">tokio</a>::<wbr><a href="index.html">io</a></div><h1>Function <span class="fn">copy_<wbr>buf</span> <button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><rustdoc-toolbar></rustdoc-toolbar><span class="sub-heading"><a class="src" href="../../src/tokio/io/util/copy_buf.rs.html#69-79">Source</a> </span></div><pre class="rust item-decl"><code>pub async fn copy_buf<'a, R, W>(
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reader: <a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.reference.html">&'a mut R</a>,
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writer: <a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.reference.html">&'a mut W</a>,
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) -> <a class="type" href="https://doc.rust-lang.org/1.93.1/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.93.1/std/primitive.u64.html">u64</a>><div class="where">where
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R: <a class="trait" href="trait.AsyncBufRead.html" title="trait tokio::io::AsyncBufRead">AsyncBufRead</a> + <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,
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W: <a class="trait" href="trait.AsyncWrite.html" title="trait tokio::io::AsyncWrite">AsyncWrite</a> + <a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Unpin.html" title="trait core::marker::Unpin">Unpin</a> + ?<a class="trait" href="https://doc.rust-lang.org/1.93.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>,</div></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Asynchronously copies the entire contents of a reader into a writer.</p>
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<p>This function returns a future that will continuously read data from
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<code>reader</code> and then write it into <code>writer</code> in a streaming fashion until
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<code>reader</code> returns EOF or fails.</p>
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<p>On success, the total number of bytes that were copied from <code>reader</code> to
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<code>writer</code> is returned.</p>
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<p>This is a <a href="fn.copy.html" title="fn tokio::io::copy"><code>tokio::io::copy</code></a> alternative for <a href="trait.AsyncBufRead.html" title="trait tokio::io::AsyncBufRead"><code>AsyncBufRead</code></a> readers
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with no extra buffer allocation, since <a href="trait.AsyncBufRead.html" title="trait tokio::io::AsyncBufRead"><code>AsyncBufRead</code></a> allow access
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to the reader’s inner buffer.</p>
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<h2 id="when-to-use-async-alternatives-instead-of-synciobridge"><a class="doc-anchor" href="#when-to-use-async-alternatives-instead-of-synciobridge">§</a>When to use async alternatives instead of <code>SyncIoBridge</code></h2>
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<p>If you are looking to use <a href="https://doc.rust-lang.org/1.93.1/std/io/copy/fn.copy.html" title="fn std::io::copy::copy"><code>std::io::copy</code></a> with a synchronous consumer
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(like a <code>hasher</code> or compressor), consider using async alternatives instead of
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wrapping the reader with <a href="https://docs.rs/tokio-util/latest/tokio_util/io/struct.SyncIoBridge.html"><code>SyncIoBridge</code></a>. See the <a href="https://docs.rs/tokio-util/latest/tokio_util/io/struct.SyncIoBridge.html"><code>SyncIoBridge</code></a>
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documentation for detailed examples and guidance on hashing, compression,
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and data parsing.</p>
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<h2 id="errors"><a class="doc-anchor" href="#errors">§</a>Errors</h2>
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<p>The returned future will finish with an error will return an error
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immediately if any call to <code>poll_fill_buf</code> or <code>poll_write</code> returns an
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error.</p>
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<h2 id="examples"><a class="doc-anchor" href="#examples">§</a>Examples</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>tokio::io;
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<span class="kw">let </span><span class="kw-2">mut </span>reader: <span class="kw-2">&</span>[u8] = <span class="string">b"hello"</span>;
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<span class="kw">let </span><span class="kw-2">mut </span>writer: Vec<u8> = <span class="macro">vec!</span>[];
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io::copy_buf(<span class="kw-2">&mut </span>reader, <span class="kw-2">&mut </span>writer).<span class="kw">await</span><span class="question-mark">?</span>;
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<span class="macro">assert_eq!</span>(<span class="string">b"hello"</span>, <span class="kw-2">&</span>writer[..]);</code></pre></div></div></details></section></div></main></body></html> |