27 lines
7.6 KiB
HTML
27 lines
7.6 KiB
HTML
<!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 `try_parse` macro in crate `nom`."><meta name="keywords" content="rust, rustlang, rust-lang, try_parse"><title>nom::try_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: 'try_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/macros.rs.html#632-644' title='goto source code'>[src]</a></span><span class='in-band'>Macro <a href='index.html'>nom</a>::<wbr><a class="macro" href=''>try_parse</a></span></h1><div class="docblock type-decl hidden-by-usual-hider"><div class="example-wrap"><pre class="rust macro">
|
||
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">try_parse</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">$</span><span class="macro-nonterminal">i</span>:<span class="ident">expr</span>, <span class="macro-nonterminal">$</span><span class="macro-nonterminal">f</span>:<span class="ident">expr</span>) <span class="op">=</span><span class="op">></span> { ... };
|
||
}</pre></div>
|
||
</div><div class='docblock'><p>A bit like <code>std::try!</code>, this macro will return the remaining input and
|
||
parsed value if the child parser returned <code>Ok</code>, and will do an early
|
||
return for the <code>Err</code> side.</p>
|
||
<p>this can provide more flexibility than <code>do_parse!</code> if needed</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered">
|
||
|
||
<span class="kw">fn</span> <span class="ident">take_add</span>(<span class="ident">input</span>:<span class="kw-2">&</span>[<span class="ident">u8</span>], <span class="ident">size</span>: <span class="ident">u8</span>) <span class="op">-</span><span class="op">></span> <span class="ident">IResult</span><span class="op"><</span><span class="kw-2">&</span>[<span class="ident">u8</span>],<span class="kw-2">&</span>[<span class="ident">u8</span>]<span class="op">></span> {
|
||
<span class="kw">let</span> (<span class="ident">i1</span>, <span class="ident">sz</span>) <span class="op">=</span> <span class="macro">try_parse</span><span class="macro">!</span>(<span class="ident">input</span>, <span class="ident">nom</span>::<span class="ident">be_u8</span>);
|
||
<span class="kw">let</span> (<span class="ident">i2</span>, <span class="ident">length</span>) <span class="op">=</span> <span class="macro">try_parse</span><span class="macro">!</span>(<span class="ident">i1</span>, <span class="macro">expr_opt</span><span class="macro">!</span>(<span class="ident">size</span>.<span class="ident">checked_add</span>(<span class="ident">sz</span>)));
|
||
<span class="kw">let</span> (<span class="ident">i3</span>, <span class="ident">data</span>) <span class="op">=</span> <span class="macro">try_parse</span><span class="macro">!</span>(<span class="ident">i2</span>, <span class="macro">take</span><span class="macro">!</span>(<span class="ident">length</span>));
|
||
<span class="kw">return</span> <span class="prelude-val">Ok</span>((<span class="ident">i3</span>, <span class="ident">data</span>));
|
||
}
|
||
<span class="kw">let</span> <span class="ident">arr1</span> <span class="op">=</span> [<span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>];
|
||
<span class="kw">let</span> <span class="ident">r1</span> <span class="op">=</span> <span class="ident">take_add</span>(<span class="kw-2">&</span><span class="ident">arr1</span>[..], <span class="number">1</span>);
|
||
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">r1</span>, <span class="prelude-val">Ok</span>((<span class="kw-2">&</span>[<span class="number">4</span>,<span class="number">5</span>][..], <span class="kw-2">&</span>[<span class="number">2</span>,<span class="number">3</span>][..])));
|
||
|
||
<span class="kw">let</span> <span class="ident">arr2</span> <span class="op">=</span> [<span class="number">0xFE</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>];
|
||
<span class="comment">// size is overflowing</span>
|
||
<span class="kw">let</span> <span class="ident">r1</span> <span class="op">=</span> <span class="ident">take_add</span>(<span class="kw-2">&</span><span class="ident">arr2</span>[..], <span class="number">42</span>);
|
||
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">r1</span>, <span class="prelude-val">Err</span>(<span class="prelude-val">Err</span>::<span class="ident">Error</span>(<span class="macro">error_position</span><span class="macro">!</span>(<span class="kw-2">&</span>[<span class="number">2</span>,<span class="number">3</span>,<span class="number">4</span>,<span class="number">5</span>][..], <span class="ident">ErrorKind</span>::<span class="ident">ExprOpt</span>))));</pre></div>
|
||
</div></section><section id="search" class="content hidden"></section><section class="footer"></section><script>window.rootPath = "../";window.currentCrate = "nom";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html> |