81 lines
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81 lines
20 KiB
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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 `do_parse` macro in crate `nom`."><meta name="keywords" content="rust, rustlang, rust-lang, do_parse"><title>nom::do_parse - 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 macro"><!--[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='../nom/index.html'><div class='logo-container'><img src='../rust-logo.png' alt='logo'></div></a><div class="sidebar-elems"><p class='location'><a href='index.html'>nom</a></p><script>window.sidebarCurrent = {name: 'do_parse', ty: 'macro', 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"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" disabled 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/nom/sequence.rs.html#305-437' title='goto source code'>[src]</a></span><span class='in-band'>Macro <a href='index.html'>nom</a>::<wbr><a class="macro" href=''>do_parse</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
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<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">do_parse</span> {
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">expr</span>),<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) ) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) ) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) ~ $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) ~ $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> ~ $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> ~ $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> <span class="op">></span><span class="op">></span> ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">></span><span class="op">></span> ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">ident</span> <span class="op">></span><span class="op">></span> ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__impl</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">ident</span> : <span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">></span><span class="op">></span> ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__finalize</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, ( <span class="macro-nonterminal">$</span><span class="macro-nonterminal">o</span>: <span class="ident">expr</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="ident">__finalize</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, ( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> )) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">submac</span>:<span class="macro">ident</span><span class="macro">!</span>( $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">args</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">=</span><span class="op">></span> { ... };
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(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="macro">ident</span><span class="macro">!</span> <span class="op">></span><span class="op">></span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="op">*</span> ) <span class="op">=</span><span class="op">></span> { ... };
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}</pre></div>
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</div><div class='docblock'><p><code>do_parse!(I->IResult<I,A> >> I->IResult<I,B> >> ... I->IResult<I,X> , ( O ) ) => I -> IResult<I, O></code>
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do_parse applies sub parsers in a sequence.
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it can store intermediary results and make them available
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for later parsers</p>
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<p>The input type <code>I</code> must implement <code>nom::InputLength</code>.</p>
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<p>This combinator will count how much data is consumed by every child parser
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and take it into account if there is not enough data</p>
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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">nom</span>::<span class="ident">be_u8</span>;
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<span class="comment">// this parser implements a common pattern in binary formats,</span>
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<span class="comment">// the TAG-LENGTH-VALUE, where you first recognize a specific</span>
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<span class="comment">// byte slice, then the next bytes indicate the length of</span>
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<span class="comment">// the data, then you take that slice and return it</span>
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<span class="comment">//</span>
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<span class="comment">// here, we match the tag 42, take the length in the next byte</span>
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<span class="comment">// and store it in `length`, then use `take!` with `length`</span>
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<span class="comment">// to obtain the subslice that we store in `bytes`, then return</span>
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<span class="comment">// `bytes`</span>
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<span class="comment">// you can use other macro combinators inside do_parse (like the `tag`</span>
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<span class="comment">// one here), or a function (like `be_u8` here), but you cannot use a</span>
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<span class="comment">// module path (like `nom::be_u8`) there, because of limitations in macros</span>
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<span class="macro">named</span><span class="macro">!</span>(<span class="ident">tag_length_value</span>,
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<span class="macro">do_parse</span><span class="macro">!</span>(
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<span class="macro">tag</span><span class="macro">!</span>( <span class="kw-2">&</span>[ <span class="number">42u8</span> ][..] ) <span class="op">></span><span class="op">></span>
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<span class="ident">length</span>: <span class="ident">be_u8</span> <span class="op">></span><span class="op">></span>
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<span class="ident">bytes</span>: <span class="macro">take</span><span class="macro">!</span>(<span class="ident">length</span>) <span class="op">></span><span class="op">></span>
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(<span class="ident">bytes</span>)
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)
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);
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<span class="kw">let</span> <span class="ident">a</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>(<span class="number">42</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>);
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<span class="kw">let</span> <span class="ident">result_a</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>(<span class="number">3</span>, <span class="number">4</span>);
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<span class="kw">let</span> <span class="ident">rest_a</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>(<span class="number">5</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">tag_length_value</span>(<span class="kw-2">&</span><span class="ident">a</span>[..]), <span class="prelude-val">Ok</span>((<span class="kw-2">&</span><span class="ident">rest_a</span>[..], <span class="kw-2">&</span><span class="ident">result_a</span>[..])));
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<span class="comment">// here, the length is 5, but there are only 3 bytes afterwards (3, 4 and 5),</span>
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<span class="comment">// so the parser will tell you that you need 7 bytes: one for the tag,</span>
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<span class="comment">// one for the length, then 5 bytes</span>
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<span class="kw">let</span> <span class="ident">b</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>(<span class="number">42</span>, <span class="number">5</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">tag_length_value</span>(<span class="kw-2">&</span><span class="ident">b</span>[..]), <span class="prelude-val">Err</span>(<span class="prelude-val">Err</span>::<span class="ident">Incomplete</span>(<span class="ident">Needed</span>::<span class="ident">Size</span>(<span class="number">5</span>))));</pre></div>
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<p>the result is a tuple, so you can return multiple sub results, like
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this:
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<code>do_parse!(I->IResult<I,A> >> I->IResult<I,B> >> ... I->IResult<I,X> , ( O, P ) ) => I -> IResult<I, (O,P)></code></p>
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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">nom</span>::<span class="ident">be_u8</span>;
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<span class="macro">named</span><span class="macro">!</span>(<span class="ident">tag_length_value</span><span class="op"><</span>(<span class="ident">u8</span>, <span class="kw-2">&</span>[<span class="ident">u8</span>])<span class="op">></span>,
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<span class="macro">do_parse</span><span class="macro">!</span>(
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<span class="macro">tag</span><span class="macro">!</span>( <span class="kw-2">&</span>[ <span class="number">42u8</span> ][..] ) <span class="op">></span><span class="op">></span>
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<span class="ident">length</span>: <span class="ident">be_u8</span> <span class="op">></span><span class="op">></span>
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<span class="ident">bytes</span>: <span class="macro">take</span><span class="macro">!</span>(<span class="ident">length</span>) <span class="op">></span><span class="op">></span>
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(<span class="ident">length</span>, <span class="ident">bytes</span>)
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)
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);
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</pre></div>
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