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<h1 class='fqn'><span class='in-band'>Module <a href='../index.html'>core</a>::<wbr><a class="mod" href=''>hash</a></span><span class='out-of-band'><span class='since' title='Stable since Rust version 1.0.0'>1.0.0</span><span id='render-detail'>
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</span><a class='srclink' href='../../src/core/hash/mod.rs.html#11-622' title='goto source code'>[src]</a></span></h1>
<div class='docblock'><p>Generic hashing support.</p>
<p>This module provides a generic way to compute the hash of a value. The
simplest way to make a type hashable is to use <code>#[derive(Hash)]</code>:</p>
<h1 id='examples' class='section-header'><a href='#examples'>Examples</a></h1>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">hash_map</span>::<span class="ident">DefaultHasher</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">hash</span>::{<span class="ident">Hash</span>, <span class="ident">Hasher</span>};
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Hash</span>)]</span>
<span class="kw">struct</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="ident">u32</span>,
<span class="ident">name</span>: <span class="ident">String</span>,
<span class="ident">phone</span>: <span class="ident">u64</span>,
}
<span class="kw">let</span> <span class="ident">person1</span> <span class="op">=</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="number">5</span>,
<span class="ident">name</span>: <span class="string">"Janet"</span>.<span class="ident">to_string</span>(),
<span class="ident">phone</span>: <span class="number">555_666_7777</span>,
};
<span class="kw">let</span> <span class="ident">person2</span> <span class="op">=</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="number">5</span>,
<span class="ident">name</span>: <span class="string">"Bob"</span>.<span class="ident">to_string</span>(),
<span class="ident">phone</span>: <span class="number">555_666_7777</span>,
};
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">calculate_hash</span>(<span class="kw-2">&</span><span class="ident">person1</span>) <span class="op">!=</span> <span class="ident">calculate_hash</span>(<span class="kw-2">&</span><span class="ident">person2</span>));
<span class="kw">fn</span> <span class="ident">calculate_hash</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Hash</span><span class="op">></span>(<span class="ident">t</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">DefaultHasher</span>::<span class="ident">new</span>();
<span class="ident">t</span>.<span class="ident">hash</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">s</span>);
<span class="ident">s</span>.<span class="ident">finish</span>()
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Acollections%3A%3Ahash_map%3A%3ADefaultHasher%3B%0Ause%20std%3A%3Ahash%3A%3A%7BHash%2C%20Hasher%7D%3B%0A%0A%23%5Bderive(Hash)%5D%0Astruct%20Person%20%7B%0A%20%20%20%20id%3A%20u32%2C%0A%20%20%20%20name%3A%20String%2C%0A%20%20%20%20phone%3A%20u64%2C%0A%7D%0A%0Alet%20person1%20%3D%20Person%20%7B%0A%20%20%20%20id%3A%205%2C%0A%20%20%20%20name%3A%20%22Janet%22.to_string()%2C%0A%20%20%20%20phone%3A%20555_666_7777%2C%0A%7D%3B%0Alet%20person2%20%3D%20Person%20%7B%0A%20%20%20%20id%3A%205%2C%0A%20%20%20%20name%3A%20%22Bob%22.to_string()%2C%0A%20%20%20%20phone%3A%20555_666_7777%2C%0A%7D%3B%0A%0Aassert!(calculate_hash(%26person1)%20!%3D%20calculate_hash(%26person2))%3B%0A%0Afn%20calculate_hash%3CT%3A%20Hash%3E(t%3A%20%26T)%20-%3E%20u64%20%7B%0A%20%20%20%20let%20mut%20s%20%3D%20DefaultHasher%3A%3Anew()%3B%0A%20%20%20%20t.hash(%26mut%20s)%3B%0A%20%20%20%20s.finish()%0A%7D%0A%7D">Run</a></pre>
<p>If you need more control over how a value is hashed, you need to implement
the <a href="trait.Hash.html"><code>Hash</code></a> trait:</p>
<pre class="rust rust-example-rendered">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">hash_map</span>::<span class="ident">DefaultHasher</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">hash</span>::{<span class="ident">Hash</span>, <span class="ident">Hasher</span>};
<span class="kw">struct</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="ident">u32</span>,
<span class="ident">name</span>: <span class="ident">String</span>,
<span class="ident">phone</span>: <span class="ident">u64</span>,
}
<span class="kw">impl</span> <span class="ident">Hash</span> <span class="kw">for</span> <span class="ident">Person</span> {
<span class="kw">fn</span> <span class="ident">hash</span><span class="op"><</span><span class="ident">H</span>: <span class="ident">Hasher</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">state</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">H</span>) {
<span class="self">self</span>.<span class="ident">id</span>.<span class="ident">hash</span>(<span class="ident">state</span>);
<span class="self">self</span>.<span class="ident">phone</span>.<span class="ident">hash</span>(<span class="ident">state</span>);
}
}
<span class="kw">let</span> <span class="ident">person1</span> <span class="op">=</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="number">5</span>,
<span class="ident">name</span>: <span class="string">"Janet"</span>.<span class="ident">to_string</span>(),
<span class="ident">phone</span>: <span class="number">555_666_7777</span>,
};
<span class="kw">let</span> <span class="ident">person2</span> <span class="op">=</span> <span class="ident">Person</span> {
<span class="ident">id</span>: <span class="number">5</span>,
<span class="ident">name</span>: <span class="string">"Bob"</span>.<span class="ident">to_string</span>(),
<span class="ident">phone</span>: <span class="number">555_666_7777</span>,
};
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">calculate_hash</span>(<span class="kw-2">&</span><span class="ident">person1</span>), <span class="ident">calculate_hash</span>(<span class="kw-2">&</span><span class="ident">person2</span>));
<span class="kw">fn</span> <span class="ident">calculate_hash</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Hash</span><span class="op">></span>(<span class="ident">t</span>: <span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">DefaultHasher</span>::<span class="ident">new</span>();
<span class="ident">t</span>.<span class="ident">hash</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">s</span>);
<span class="ident">s</span>.<span class="ident">finish</span>()
}<a class="test-arrow" target="_blank" href="https://play.rust-lang.org/?code=fn%20main()%20%7B%0Ause%20std%3A%3Acollections%3A%3Ahash_map%3A%3ADefaultHasher%3B%0Ause%20std%3A%3Ahash%3A%3A%7BHash%2C%20Hasher%7D%3B%0A%0Astruct%20Person%20%7B%0A%20%20%20%20id%3A%20u32%2C%0A%23%5Ballow(dead_code)%5D%0A%20%20%20%20name%3A%20String%2C%0A%20%20%20%20phone%3A%20u64%2C%0A%7D%0A%0Aimpl%20Hash%20for%20Person%20%7B%0A%20%20%20%20fn%20hash%3CH%3A%20Hasher%3E(%26self%2C%20state%3A%20%26mut%20H)%20%7B%0A%20%20%20%20%20%20%20%20self.id.hash(state)%3B%0A%20%20%20%20%20%20%20%20self.phone.hash(state)%3B%0A%20%20%20%20%7D%0A%7D%0A%0Alet%20person1%20%3D%20Person%20%7B%0A%20%20%20%20id%3A%205%2C%0A%20%20%20%20name%3A%20%22Janet%22.to_string()%2C%0A%20%20%20%20phone%3A%20555_666_7777%2C%0A%7D%3B%0Alet%20person2%20%3D%20Person%20%7B%0A%20%20%20%20id%3A%205%2C%0A%20%20%20%20name%3A%20%22Bob%22.to_string()%2C%0A%20%20%20%20phone%3A%20555_666_7777%2C%0A%7D%3B%0A%0Aassert_eq!(calculate_hash(%26person1)%2C%20calculate_hash(%26person2))%3B%0A%0Afn%20calculate_hash%3CT%3A%20Hash%3E(t%3A%20%26T)%20-%3E%20u64%20%7B%0A%20%20%20%20let%20mut%20s%20%3D%20DefaultHasher%3A%3Anew()%3B%0A%20%20%20%20t.hash(%26mut%20s)%3B%0A%20%20%20%20s.finish()%0A%7D%0A%7D">Run</a></pre>
</div><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
<table>
<tr class=' module-item'>
<td><a class="struct" href="struct.BuildHasherDefault.html"
title='struct core::hash::BuildHasherDefault'>BuildHasherDefault</a></td>
<td class='docblock-short'>
<p>Used to create a default <a href="trait.BuildHasher.html"><code>BuildHasher</code></a> instance for types that implement
<a href="trait.Hasher.html"><code>Hasher</code></a> and <a href="../default/trait.Default.html"><code>Default</code></a>.</p>
</td>
</tr>
<tr class='deprecated module-item'>
<td><a class="struct" href="struct.SipHasher.html"
title='struct core::hash::SipHasher'>SipHasher</a></td>
<td class='docblock-short'>
[<div class='stab deprecated'>Deprecated</div>] <p>An implementation of SipHash 2-4.</p>
</td>
</tr>
<tr class='unstable deprecated module-item'>
<td><a class="struct" href="struct.SipHasher13.html"
title='struct core::hash::SipHasher13'>SipHasher13</a></td>
<td class='docblock-short'>
[<div class='stab deprecated'>Deprecated</div>] [<div class='stab unstable'>Experimental</div>] <p>An implementation of SipHash 1-3.</p>
</td>
</tr>
<tr class='unstable deprecated module-item'>
<td><a class="struct" href="struct.SipHasher24.html"
title='struct core::hash::SipHasher24'>SipHasher24</a></td>
<td class='docblock-short'>
[<div class='stab deprecated'>Deprecated</div>] [<div class='stab unstable'>Experimental</div>] <p>An implementation of SipHash 2-4.</p>
</td>
</tr></table><h2 id='traits' class='section-header'><a href="#traits">Traits</a></h2>
<table>
<tr class=' module-item'>
<td><a class="trait" href="trait.BuildHasher.html"
title='trait core::hash::BuildHasher'>BuildHasher</a></td>
<td class='docblock-short'>
<p>A trait for creating instances of <a href="trait.Hasher.html"><code>Hasher</code></a>.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.Hash.html"
title='trait core::hash::Hash'>Hash</a></td>
<td class='docblock-short'>
<p>A hashable type.</p>
</td>
</tr>
<tr class=' module-item'>
<td><a class="trait" href="trait.Hasher.html"
title='trait core::hash::Hasher'>Hasher</a></td>
<td class='docblock-short'>
<p>A trait for hashing an arbitrary stream of bytes.</p>
</td>
</tr></table></section>
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