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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="Generate a corresponding `VarULE` type and the relevant `EncodeAsVarULE`/[`zerofrom::ZeroFrom`] implementations for this type"><title>make_varule in zerovec - 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="zerovec" 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 attr"><!--[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="#">make_varule</a></h2></rustdoc-topbar><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../zerovec/index.html">zerovec</a><span class="version">0.11.5</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">make_<wbr>varule</a></h2><h3><a href="#">Sections</a></h3><ul class="block top-toc"><li><a href="#example" title="Example">Example</a></li></ul></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate zerovec</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">zerovec</a></div><h1>Attribute Macro <span class="attr">make_<wbr>varule</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/zerovec_derive/lib.rs.html#39">Source</a> </span></div><pre class="rust item-decl"><code>#[make_varule]</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Generate a corresponding <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> type and the relevant <a href="ule/trait.EncodeAsVarULE.html" title="trait zerovec::ule::EncodeAsVarULE"><code>EncodeAsVarULE</code></a>/<a href="../zerofrom/zero_from/trait.ZeroFrom.html" title="trait zerofrom::zero_from::ZeroFrom"><code>zerofrom::ZeroFrom</code></a>
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implementations for this type</p>
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<p>This can be attached to structs containing only <a href="ule/trait.AsULE.html" title="trait zerovec::ule::AsULE"><code>AsULE</code></a> types with the last fields being
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<a href="alloc::borrow::Cow"><code>Cow<'a, str></code></a>, <a href="struct.ZeroSlice.html" title="struct zerovec::ZeroSlice"><code>ZeroSlice</code></a>, or <a href="struct.VarZeroSlice.html" title="struct zerovec::VarZeroSlice"><code>VarZeroSlice</code></a>. If there is more than one such field, it will be represented
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using <a href="ule/struct.MultiFieldsULE.html" title="struct zerovec::ule::MultiFieldsULE"><code>MultiFieldsULE</code></a> and getters will be generated. Other VarULE fields will be detected if they are
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tagged with <code>#[zerovec::varule(NameOfVarULETy)]</code>.</p>
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<p>The type must be <a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.PartialEq.html" title="trait core::cmp::PartialEq"><code>PartialEq</code></a> and <a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.Eq.html" title="trait core::cmp::Eq"><code>Eq</code></a>.</p>
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<p><a href="ule/trait.EncodeAsVarULE.html" title="trait zerovec::ule::EncodeAsVarULE"><code>EncodeAsVarULE</code></a> and <a href="../zerofrom/zero_from/trait.ZeroFrom.html" title="trait zerofrom::zero_from::ZeroFrom"><code>zerofrom::ZeroFrom</code></a> are useful for avoiding the need to deal with
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the <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> type directly. In particular, it is recommended to use <a href="../zerofrom/zero_from/trait.ZeroFrom.html" title="trait zerofrom::zero_from::ZeroFrom"><code>zerofrom::ZeroFrom</code></a>
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to convert the <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> type back to this type in a cheap, zero-copy way (see the example below
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for more details).</p>
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<p><code>#[make_varule]</code> will automatically derive the following traits on the <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> type:</p>
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<ul>
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<li><a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.Ord.html" title="trait core::cmp::Ord"><code>Ord</code></a> and <a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd"><code>PartialOrd</code></a></li>
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<li><a href="maps::ZeroMapKV"><code>ZeroMapKV</code></a></li>
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<li>[<code>alloc::borrow::ToOwned</code>]</li>
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</ul>
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<p>To disable one of the automatic derives, use <code>#[zerovec::skip_derive(...)]</code> like so: <code>#[zerovec::skip_derive(ZeroMapKV)]</code>.
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<code>Ord</code> and <code>PartialOrd</code> are implemented as a unit and can only be disabled as a group with <code>#[zerovec::skip_derive(Ord)]</code>.</p>
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<p>The following traits are available to derive, but not automatic:</p>
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<ul>
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<li><a href="https://doc.rust-lang.org/1.93.1/core/fmt/macros/derive.Debug.html" title="derive core::fmt::macros::Debug"><code>Debug</code></a></li>
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<li><a href="serde::Serialize"><code>Serialize</code></a></li>
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<li><a href="serde::Deserialize"><code>Deserialize</code></a></li>
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</ul>
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<p>To enable one of these additional derives, use <code>#[zerovec::derive(...)]</code> like so: <code>#[zerovec::derive(Debug)]</code>.</p>
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<p>In most cases these derives will defer to the impl of the same trait on the current type, so such impls must exist.</p>
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<p>This implementation will also by default autogenerate <a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.Ord.html" title="trait core::cmp::Ord"><code>Ord</code></a> and <a href="https://doc.rust-lang.org/1.93.1/core/cmp/trait.PartialOrd.html" title="trait core::cmp::PartialOrd"><code>PartialOrd</code></a> on the <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> type based on
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the implementation on <code>Self</code>. You can opt out of this with <code>#[zerovec::skip_derive(Ord)]</code></p>
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<p>Note that this implementation will autogenerate <a href="ule/trait.EncodeAsVarULE.html" title="trait zerovec::ule::EncodeAsVarULE"><code>EncodeAsVarULE</code></a> impls for <em>both</em> <code>Self</code> and <code>&Self</code>
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for convenience. This allows for a little more flexibility encoding slices.</p>
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<p>In case there are multiple <a href="ule/trait.VarULE.html" title="trait zerovec::ule::VarULE"><code>VarULE</code></a> (i.e., variable-sized) fields, this macro will produce private fields that
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appropriately pack the data together, with the packing format by default being <a href="vecs/struct.Index16.html" title="struct zerovec::vecs::Index16"><code>crate::vecs::Index16</code></a>, but can be
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overridden with <code>#[zerovec::format(zerovec::vecs::Index8)]</code>.</p>
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<h2 id="example"><a class="doc-anchor" href="#example">§</a>Example</h2>
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<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>std::borrow::Cow;
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<span class="kw">use </span>zerofrom::ZeroFrom;
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<span class="kw">use </span>zerovec::ule::encode_varule_to_box;
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<span class="kw">use </span>zerovec::{VarZeroVec, ZeroMap, ZeroVec};
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<span class="comment">// custom fixed-size ULE type for ZeroVec
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</span><span class="attr">#[zerovec::make_ule(DateULE)]
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#[derive(Copy, Clone, PartialEq, Eq, Ord, PartialOrd, serde::Serialize, serde::Deserialize)]
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</span><span class="kw">struct </span>Date {
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y: u64,
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m: u8,
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d: u8,
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}
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<span class="comment">// custom variable sized VarULE type for VarZeroVec
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</span><span class="attr">#[zerovec::make_varule(PersonULE)]
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#[zerovec::derive(Serialize, Deserialize)]
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#[derive(Clone, PartialEq, Eq, Ord, PartialOrd, serde::Serialize, serde::Deserialize)]
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</span><span class="kw">struct </span>Person<<span class="lifetime">'a</span>> {
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birthday: Date,
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favorite_character: char,
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<span class="attr">#[serde(borrow)]
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</span>name: Cow<<span class="lifetime">'a</span>, str>,
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}
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<span class="attr">#[derive(serde::Serialize, serde::Deserialize)]
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</span><span class="kw">struct </span>Data<<span class="lifetime">'a</span>> {
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<span class="comment">// note: VarZeroVec always must reference the ULE type directly
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</span><span class="attr">#[serde(borrow)]
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</span>important_people: VarZeroVec<<span class="lifetime">'a</span>, PersonULE>,
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}
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<span class="kw">let </span>person1 = Person {
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birthday: Date {
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y: <span class="number">1990</span>,
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m: <span class="number">9</span>,
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d: <span class="number">7</span>,
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},
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favorite_character: <span class="string">'π'</span>,
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name: Cow::from(<span class="string">"Kate"</span>),
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};
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<span class="kw">let </span>person2 = Person {
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birthday: Date {
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y: <span class="number">1960</span>,
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m: <span class="number">5</span>,
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d: <span class="number">25</span>,
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},
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favorite_character: <span class="string">'冇'</span>,
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name: Cow::from(<span class="string">"Jesse"</span>),
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};
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<span class="kw">let </span>important_people = VarZeroVec::from(<span class="kw-2">&</span>[person1, person2]);
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<span class="kw">let </span>data = Data { important_people };
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<span class="kw">let </span>bincode_bytes = bincode::serialize(<span class="kw-2">&</span>data).expect(<span class="string">"Serialization should be successful"</span>);
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<span class="comment">// Will deserialize without allocations
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</span><span class="kw">let </span>deserialized: Data =
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bincode::deserialize(<span class="kw-2">&</span>bincode_bytes).expect(<span class="string">"Deserialization should be successful"</span>);
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<span class="macro">assert_eq!</span>(<span class="kw-2">&</span>deserialized.important_people.get(<span class="number">1</span>).unwrap().name, <span class="string">"Jesse"</span>);
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<span class="macro">assert_eq!</span>(<span class="kw-2">&</span>deserialized.important_people.get(<span class="number">0</span>).unwrap().name, <span class="string">"Kate"</span>);
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<span class="comment">// Since VarZeroVec produces PersonULE types, it's convenient to use ZeroFrom
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// to recoup Person values in a zero-copy way
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</span><span class="kw">let </span>person_converted: Person =
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ZeroFrom::zero_from(deserialized.important_people.get(<span class="number">1</span>).unwrap());
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<span class="macro">assert_eq!</span>(person_converted.name, <span class="string">"Jesse"</span>);
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<span class="macro">assert_eq!</span>(person_converted.birthday.y, <span class="number">1960</span>);</code></pre></div>
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<p>Full docs for this proc macro can be found on the <a href="https://docs.rs/zerovec"><code>zerovec</code></a> crate.</p>
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</div></details></section></div></main></body></html> |