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  1. <!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 `EntropyRng` struct in crate `rand`."><meta name="keywords" content="rust, rustlang, rust-lang, EntropyRng"><title>rand::rngs::EntropyRng - 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><link rel="shortcut icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc struct"><!--[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">&#9776;</div><a href='../../rand/index.html'><img src='https://www.rust-lang.org/logos/rust-logo-128x128-blk.png' alt='logo' width='100'></a><p class='location'>Struct EntropyRng</p><div class="sidebar-elems"><div class="block items"><a class="sidebar-title" href="#methods">Methods</a><div class="sidebar-links"><a href="#method.new">new</a></div><a class="sidebar-title" href="#implementations">Trait Implementations</a><div class="sidebar-links"><a href="#impl-Debug">Debug</a><a href="#impl-Default">Default</a><a href="#impl-RngCore">RngCore</a><a href="#impl-CryptoRng">CryptoRng</a></div><a class="sidebar-title" href="#synthetic-implementations">Auto Trait Implementations</a><div class="sidebar-links"><a href="#impl-Send">Send</a><a href="#impl-Sync">Sync</a></div></div><p class='location'><a href='../index.html'>rand</a>::<wbr><a href='index.html'>rngs</a></p><script>window.sidebarCurrent = {name: 'EntropyRng', ty: 'struct', 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"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><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='in-band'>Struct <a href='../index.html'>rand</a>::<wbr><a href='index.html'>rngs</a>::<wbr><a class="struct" href=''>EntropyRng</a></span><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'>&#x2212;</span>]</a></span><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#49-51' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class='rust struct'>pub struct EntropyRng { /* fields omitted */ }</pre></div><div class='docblock'><p>An interface returning random data from external source(s), provided
    2. 

  2. specifically for securely seeding algorithmic generators (PRNGs).</p>
    3. 

  3. <p>Where possible, <code>EntropyRng</code> retrieves random data from the operating
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  4. system's interface for random numbers (<a href="struct.OsRng.html"><code>OsRng</code></a>); if that fails it will
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  5. fall back to the <a href="jitter/struct.JitterRng.html"><code>JitterRng</code></a> entropy collector. In the latter case it will
    6. 

  6. still try to use <a href="struct.OsRng.html"><code>OsRng</code></a> on the next usage.</p>
    7. 

  7. <p>If no secure source of entropy is available <code>EntropyRng</code> will panic on use;
    8. 

  8. i.e. it should never output predictable data.</p>
    9. 

  9. <p>This is either a little slow (<a href="struct.OsRng.html"><code>OsRng</code></a> requires a system call) or extremely
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  10. slow (<a href="jitter/struct.JitterRng.html"><code>JitterRng</code></a> must use significant CPU time to generate sufficient
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  11. jitter); for better performance it is common to seed a local PRNG from
    12. 

  12. external entropy then primarily use the local PRNG (<a href="../fn.thread_rng.html"><code>thread_rng</code></a> is
    13. 

  13. provided as a convenient, local, automatically-seeded CSPRNG).</p>
    14. 

  14. <h1 id="panics" class="section-header"><a href="#panics">Panics</a></h1>
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  15. <p>On most systems, like Windows, Linux, macOS and *BSD on common hardware, it
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  16. is highly unlikely for both <a href="struct.OsRng.html"><code>OsRng</code></a> and <a href="jitter/struct.JitterRng.html"><code>JitterRng</code></a> to fail. But on
    17. 

  17. combinations like webassembly without Emscripten or stdweb both sources are
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  18. unavailable. If both sources fail, only <a href="../trait.RngCore.html#method.tymethod.try_fill_bytes"><code>try_fill_bytes</code></a> is able to
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  19. report the error, and only the one from <code>OsRng</code>. The other <a href="../trait.RngCore.html"><code>RngCore</code></a>
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  20. methods will panic in case of an error.</p>
    21. 

  21. </div>
    22. 

  22.                     <h2 id='methods' class='small-section-header'>
    23. 

  23.                       Methods<a href='#methods' class='anchor'></a>
    24. 

  24.                     </h2>
    25. 

  25.                 <h3 id='impl' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#61-70' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.new' class="method"><span id='new.v' class='invisible'><table class='table-display'><tbody><tr><td><code>pub fn <a href='#method.new' class='fnname'>new</a>() -&gt; Self</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#67-69' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Create a new <code>EntropyRng</code>.</p>
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  26. <p>This method will do no system calls or other initialization routines,
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  27. those are done on first use. This is done to make <code>new</code> infallible,
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  28. and <code>try_fill_bytes</code> the only place to report errors.</p>
    29. 

  29. </div></div>
    30. 

  30.                 <h2 id='implementations' class='small-section-header'>
    31. 

  31.                   Trait Implementations<a href='#implementations' class='anchor'></a>
    32. 

  32.                 </h2>
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  33.                 <div id='implementations-list'><h3 id='impl-Debug' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html" title="trait core::fmt::Debug">Debug</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-Debug' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#48' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.fmt' class="method"><span id='fmt.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt' class='fnname'>fmt</a>(&amp;self, f: &amp;mut <a class="struct" href="https://doc.rust-lang.org/nightly/core/fmt/struct.Formatter.html" title="struct core::fmt::Formatter">Formatter</a>) -&gt; <a class="type" href="https://doc.rust-lang.org/nightly/core/fmt/type.Result.html" title="type core::fmt::Result">Result</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#48' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Formats the value using the given formatter. <a href="https://doc.rust-lang.org/nightly/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></p>
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  34. </div></div><h3 id='impl-Default' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html" title="trait core::default::Default">Default</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-Default' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#72-76' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.default' class="method"><span id='default.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default' class='fnname'>default</a>() -&gt; Self</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#73-75' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Returns the &quot;default value&quot; for a type. <a href="https://doc.rust-lang.org/nightly/core/default/trait.Default.html#tymethod.default">Read more</a></p>
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  35. </div></div><h3 id='impl-RngCore' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="../../rand/trait.RngCore.html" title="trait rand::RngCore">RngCore</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-RngCore' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#78-163' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'><h4 id='method.next_u32' class="method"><span id='next_u32.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../rand/trait.RngCore.html#tymethod.next_u32' class='fnname'>next_u32</a>(&amp;mut self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u32.html">u32</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#79-81' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Return the next random <code>u32</code>. <a href="../../rand/trait.RngCore.html#tymethod.next_u32">Read more</a></p>
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  36. </div><h4 id='method.next_u64' class="method"><span id='next_u64.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../rand/trait.RngCore.html#tymethod.next_u64' class='fnname'>next_u64</a>(&amp;mut self) -&gt; <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u64.html">u64</a></code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#83-85' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Return the next random <code>u64</code>. <a href="../../rand/trait.RngCore.html#tymethod.next_u64">Read more</a></p>
    37. 

  37. </div><h4 id='method.fill_bytes' class="method"><span id='fill_bytes.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../rand/trait.RngCore.html#tymethod.fill_bytes' class='fnname'>fill_bytes</a>(&amp;mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&amp;mut [</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a>)</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#87-90' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Fill <code>dest</code> with random data. <a href="../../rand/trait.RngCore.html#tymethod.fill_bytes">Read more</a></p>
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  38. </div><h4 id='method.try_fill_bytes' class="method"><span id='try_fill_bytes.v' class='invisible'><table class='table-display'><tbody><tr><td><code>fn <a href='../../rand/trait.RngCore.html#tymethod.try_fill_bytes' class='fnname'>try_fill_bytes</a>(&amp;mut self, dest: <a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">&amp;mut [</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.u8.html">u8</a><a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.slice.html">]</a>) -&gt; <a class="enum" href="https://doc.rust-lang.org/nightly/core/result/enum.Result.html" title="enum core::result::Result">Result</a>&lt;<a class="primitive" href="https://doc.rust-lang.org/nightly/std/primitive.unit.html">()</a>, <a class="struct" href="../../rand/struct.Error.html" title="struct rand::Error">Error</a>&gt;</code></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#92-162' title='goto source code'>[src]</a></td></tr></tbody></table></span></h4><div class='docblock'><p>Fill <code>dest</code> entirely with random data. <a href="../../rand/trait.RngCore.html#tymethod.try_fill_bytes">Read more</a></p>
    39. 

  39. </div></div><h3 id='impl-CryptoRng' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="../../rand/trait.CryptoRng.html" title="trait rand::CryptoRng">CryptoRng</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-CryptoRng' class='anchor'></a></span></td><td><span class='out-of-band'><div class='ghost'></div><a class='srclink' href='../../src/rand/rngs/entropy.rs.html#165' title='goto source code'>[src]</a></span></td></tr></tbody></table></h3><div class='impl-items'></div></div>
    40. 

  40.                 <h2 id='synthetic-implementations' class='small-section-header'>
    41. 

  41.                   Auto Trait Implementations<a href='#synthetic-implementations' class='anchor'></a>
    42. 

  42.                 </h2>
    43. 

  43.                 <div id='synthetic-implementations-list'>
    44. 

  44.             <h3 id='impl-Send' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-Send' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div><h3 id='impl-Sync' class='impl'><span class='in-band'><table class='table-display'><tbody><tr><td><code>impl <a class="trait" href="https://doc.rust-lang.org/nightly/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> for <a class="struct" href="../../rand/rngs/struct.EntropyRng.html" title="struct rand::rngs::EntropyRng">EntropyRng</a></code><a href='#impl-Sync' class='anchor'></a></span></td><td><span class='out-of-band'></span></td></tr></tbody></table></h3><div class='impl-items'></div></div></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>&#9166;</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../../";window.currentCrate = "rand";</script><script src="../../aliases.js"></script><script src="../../main.js"></script><script defer src="../../search-index.js"></script></body></html>
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