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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="API documentation for the Rust `IOread` trait in crate `scroll`."><meta name="keywords" content="rust, rustlang, rust-lang, IOread"><title>scroll::IOread - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script><noscript><link rel="stylesheet" href="../noscript.css"></noscript><link rel="shortcut icon" href="../favicon.ico"><style type="text/css">#crate-search{background-image:url("../down-arrow.svg");}</style></head><body class="rustdoc trait"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../scroll/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><p class='location'>Trait IOread</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#provided-methods">Provided Methods</a><div class="sidebar-links"><a href="#method.ioread">ioread</a><a href="#method.ioread_with">ioread_with</a></div><a class="sidebar-title" href="#implementors">Implementors</a></div><p class='location'><a href='index.html'>scroll</a></p><script>window.sidebarCurrent = {name: 'IOread', ty: 'trait', relpath: ''};</script><script defer src="sidebar-items.js"></script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/scroll/lesser.rs.html#53-105' title='goto source code'>[src]</a></span><span class='in-band'>Trait <a href='index.html'>scroll</a>::<wbr><a class="trait" href=''>IOread</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><pre class='rust trait'>pub trait IOread<Ctx: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a>>: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> {
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fn <a href='#method.ioread' class='fnname'>ioread</a><N: <a class="trait" href="../scroll/ctx/trait.FromCtx.html" title="trait scroll::ctx::FromCtx">FromCtx</a><Ctx> + <a class="trait" href="../scroll/ctx/trait.SizeWith.html" title="trait scroll::ctx::SizeWith">SizeWith</a><Ctx, Units = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>>>(<br> &mut self<br> ) -> <a class="type" href="https://doc.rust-lang.org/nightly/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><N><br> <span class="where">where<br> Ctx: <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a></span>,
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{ ... }
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<div class='item-spacer'></div> fn <a href='#method.ioread_with' class='fnname'>ioread_with</a><N: <a class="trait" href="../scroll/ctx/trait.FromCtx.html" title="trait scroll::ctx::FromCtx">FromCtx</a><Ctx> + <a class="trait" href="../scroll/ctx/trait.SizeWith.html" title="trait scroll::ctx::SizeWith">SizeWith</a><Ctx, Units = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>>>(<br> &mut self, <br> ctx: Ctx<br> ) -> <a class="type" href="https://doc.rust-lang.org/nightly/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><N> { ... }
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}</pre></div><div class='docblock'><p>An extension trait to <code>std::io::Read</code> streams; this only deserializes simple types, like <code>u8</code>, <code>i32</code>, <code>f32</code>, <code>usize</code>, etc.</p>
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<p>If you implement <a href="trait.FromCtx.html"><code>FromCtx</code></a> and <a href="ctx/trait.SizeWith.html"><code>SizeWith</code></a> for your type, you can then <code>ioread::<YourType>()</code> on a <code>Read</code>. Note: <a href="trait.FromCtx.html"><code>FromCtx</code></a> is only meant for very simple types, and should <em>never</em> fail.</p>
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<p><strong>NB</strong> You should probably add <code>repr(packed)</code> or <code>repr(C)</code> and be very careful how you implement <a href="ctx/trait.SizeWith.html"><code>SizeWith</code></a>, otherwise you
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will get IO errors failing to fill entire buffer (the size you specified in <code>SizeWith</code>), or out of bound errors (depending on your impl) in <code>from_ctx</code></p>
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<h1 id="example" class="section-header"><a href="#example">Example</a></h1>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::<span class="ident">Cursor</span>;
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<span class="kw">use</span> <span class="ident">scroll</span>::{<span class="self">self</span>, <span class="ident">ctx</span>, <span class="ident">LE</span>, <span class="ident">Pread</span>, <span class="ident">IOread</span>};
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<span class="attribute">#[<span class="ident">repr</span>(<span class="ident">packed</span>)]</span>
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<span class="kw">struct</span> <span class="ident">Foo</span> {
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<span class="ident">foo</span>: <span class="ident">i64</span>,
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<span class="ident">bar</span>: <span class="ident">u32</span>,
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}
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<span class="kw">impl</span> <span class="ident">ctx</span>::<span class="ident">FromCtx</span><span class="op"><</span><span class="ident">scroll</span>::<span class="ident">Endian</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Foo</span> {
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<span class="kw">fn</span> <span class="ident">from_ctx</span>(<span class="ident">bytes</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">ctx</span>: <span class="ident">scroll</span>::<span class="ident">Endian</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
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<span class="ident">Foo</span> { <span class="ident">foo</span>: <span class="ident">bytes</span>.<span class="ident">pread_with</span>::<span class="op"><</span><span class="ident">i64</span><span class="op">></span>(<span class="number">0</span>, <span class="ident">ctx</span>).<span class="ident">unwrap</span>(), <span class="ident">bar</span>: <span class="ident">bytes</span>.<span class="ident">pread_with</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>(<span class="number">8</span>, <span class="ident">ctx</span>).<span class="ident">unwrap</span>() }
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}
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}
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<span class="kw">impl</span> <span class="ident">ctx</span>::<span class="ident">SizeWith</span><span class="op"><</span><span class="ident">scroll</span>::<span class="ident">Endian</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Foo</span> {
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<span class="kw">type</span> <span class="ident">Units</span> <span class="op">=</span> <span class="ident">usize</span>;
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<span class="comment">// our parsing context doesn't influence our size</span>
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<span class="kw">fn</span> <span class="ident">size_with</span>(<span class="kw">_</span>: <span class="kw-2">&</span><span class="ident">scroll</span>::<span class="ident">Endian</span>) <span class="op">-</span><span class="op">></span> <span class="self">Self</span>::<span class="ident">Units</span> {
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::<span class="ident">std</span>::<span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">Foo</span><span class="op">></span>()
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}
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}
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<span class="kw">let</span> <span class="ident">bytes_</span> <span class="op">=</span> [<span class="number">0x0b</span>,<span class="number">0x0b</span>,<span class="number">0x00</span>,<span class="number">0x00</span>,<span class="number">0x00</span>,<span class="number">0x00</span>,<span class="number">0x00</span>,<span class="number">0x00</span>, <span class="number">0xef</span>,<span class="number">0xbe</span>,<span class="number">0x00</span>,<span class="number">0x00</span>,];
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="ident">Cursor</span>::<span class="ident">new</span>(<span class="ident">bytes_</span>);
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<span class="kw">let</span> <span class="ident">foo</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">i64</span><span class="op">></span>(<span class="ident">LE</span>).<span class="ident">unwrap</span>();
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<span class="kw">let</span> <span class="ident">bar</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>(<span class="ident">LE</span>).<span class="ident">unwrap</span>();
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">foo</span>, <span class="number">0xb0b</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">bar</span>, <span class="number">0xbeef</span>);
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<span class="kw">let</span> <span class="ident">error</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">f64</span><span class="op">></span>(<span class="ident">LE</span>);
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<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">error</span>.<span class="ident">is_err</span>());
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="ident">Cursor</span>::<span class="ident">new</span>(<span class="ident">bytes_</span>);
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<span class="kw">let</span> <span class="ident">foo_</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">Foo</span><span class="op">></span>(<span class="ident">LE</span>).<span class="ident">unwrap</span>();
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<span class="comment">// Remember that you need to copy out fields from packed structs</span>
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<span class="comment">// with a `{}` block instead of borrowing them directly</span>
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<span class="comment">// ref: https://github.com/rust-lang/rust/issues/46043</span>
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<span class="macro">assert_eq</span><span class="macro">!</span>({<span class="ident">foo_</span>.<span class="ident">foo</span>}, <span class="ident">foo</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>({<span class="ident">foo_</span>.<span class="ident">bar</span>}, <span class="ident">bar</span>);</pre></div>
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</div>
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<h2 id='provided-methods' class='small-section-header'>Provided methods<a href='#provided-methods' class='anchor'></a></h2><div class='methods'><h3 id='method.ioread' class='method'><code id='ioread.v'>fn <a href='#method.ioread' class='fnname'>ioread</a><N: <a class="trait" href="../scroll/ctx/trait.FromCtx.html" title="trait scroll::ctx::FromCtx">FromCtx</a><Ctx> + <a class="trait" href="../scroll/ctx/trait.SizeWith.html" title="trait scroll::ctx::SizeWith">SizeWith</a><Ctx, Units = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>>>(<br> &mut self<br>) -> <a class="type" href="https://doc.rust-lang.org/nightly/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><N> <span class="where fmt-newline">where<br> Ctx: <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a>, </span></code></h3><div class='docblock'><p>Reads the type <code>N</code> from <code>Self</code>, with a default parsing context.
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For the primitive numeric types, this will be at the host machine's endianness.</p>
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<h1 id="example-1" class="section-header"><a href="#example-1">Example</a></h1>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">scroll</span>::<span class="ident">IOread</span>;
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::<span class="ident">Cursor</span>;
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<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> [<span class="number">0xef</span>, <span class="number">0xbe</span>];
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="ident">Cursor</span>::<span class="ident">new</span>(<span class="kw-2">&</span><span class="ident">bytes</span>[..]);
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<span class="kw">let</span> <span class="ident">beef</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread</span>::<span class="op"><</span><span class="ident">u16</span><span class="op">></span>().<span class="ident">unwrap</span>();
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<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_endian</span> <span class="op">=</span> <span class="string">"little"</span>)]</span>
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xbeef</span>, <span class="ident">beef</span>);
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<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">target_endian</span> <span class="op">=</span> <span class="string">"big"</span>)]</span>
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xefbe</span>, <span class="ident">beef</span>);</pre></div>
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</div><h3 id='method.ioread_with' class='method'><code id='ioread_with.v'>fn <a href='#method.ioread_with' class='fnname'>ioread_with</a><N: <a class="trait" href="../scroll/ctx/trait.FromCtx.html" title="trait scroll::ctx::FromCtx">FromCtx</a><Ctx> + <a class="trait" href="../scroll/ctx/trait.SizeWith.html" title="trait scroll::ctx::SizeWith">SizeWith</a><Ctx, Units = <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.usize.html">usize</a>>>(<br> &mut self, <br> ctx: Ctx<br>) -> <a class="type" href="https://doc.rust-lang.org/nightly/std/io/error/type.Result.html" title="type std::io::error::Result">Result</a><N></code></h3><div class='docblock'><p>Reads the type <code>N</code> from <code>Self</code>, with the parsing context <code>ctx</code>.
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<strong>NB</strong>: this will panic if the type you're reading has a size greater than 256. Plans are to have this allocate in larger cases.</p>
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<p>For the primitive numeric types, this will be at the host machine's endianness.</p>
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<h1 id="example-2" class="section-header"><a href="#example-2">Example</a></h1>
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<div class="example-wrap"><pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">scroll</span>::{<span class="ident">IOread</span>, <span class="ident">LE</span>, <span class="ident">BE</span>};
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::<span class="ident">Cursor</span>;
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<span class="kw">let</span> <span class="ident">bytes</span> <span class="op">=</span> [<span class="number">0xef</span>, <span class="number">0xbe</span>, <span class="number">0xb0</span>, <span class="number">0xb0</span>, <span class="number">0xfe</span>, <span class="number">0xed</span>, <span class="number">0xde</span>, <span class="number">0xad</span>];
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<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">bytes</span> <span class="op">=</span> <span class="ident">Cursor</span>::<span class="ident">new</span>(<span class="kw-2">&</span><span class="ident">bytes</span>[..]);
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<span class="kw">let</span> <span class="ident">beef</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">u16</span><span class="op">></span>(<span class="ident">LE</span>).<span class="ident">unwrap</span>();
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xbeef</span>, <span class="ident">beef</span>);
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<span class="kw">let</span> <span class="ident">b0</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread</span>::<span class="op"><</span><span class="ident">u8</span><span class="op">></span>().<span class="ident">unwrap</span>();
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xb0</span>, <span class="ident">b0</span>);
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<span class="kw">let</span> <span class="ident">b0</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread</span>::<span class="op"><</span><span class="ident">u8</span><span class="op">></span>().<span class="ident">unwrap</span>();
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xb0</span>, <span class="ident">b0</span>);
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<span class="kw">let</span> <span class="ident">feeddead</span> <span class="op">=</span> <span class="ident">bytes</span>.<span class="ident">ioread_with</span>::<span class="op"><</span><span class="ident">u32</span><span class="op">></span>(<span class="ident">BE</span>).<span class="ident">unwrap</span>();
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0xfeeddead</span>, <span class="ident">feeddead</span>);</pre></div>
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</div></div><span class='loading-content'>Loading content...</span>
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<h2 id='implementors' class='small-section-header'>Implementors<a href='#implementors' class='anchor'></a></h2><div class='item-list' id='implementors-list'><h3 id='impl-IOread%3CCtx%3E' class='impl'><code class='in-band'>impl<Ctx: <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html" title="trait core::marker::Copy">Copy</a>, R: <a class="trait" href="https://doc.rust-lang.org/nightly/std/io/trait.Read.html" title="trait std::io::Read">Read</a> + ?<a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a>> IOread<Ctx> for R</code><a href='#impl-IOread%3CCtx%3E' class='anchor'></a><a class='srclink' href='../src/scroll/lesser.rs.html#109' title='goto source code'>[src]</a></h3><div class='docblock'><p>Types that implement <code>Read</code> get methods defined in <code>IOread</code>
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for free.</p>
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</div><div class='impl-items'></div></div><span class='loading-content'>Loading content...</span><script type="text/javascript">window.inlined_types=new Set([]);</script><script type="text/javascript" async
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src="../implementors/scroll/trait.IOread.js">
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