mirror of
https://github.com/NotAShelf/mpvrc.git
synced 2026-04-16 16:03:48 +00:00
110 lines
No EOL
18 KiB
HTML
110 lines
No EOL
18 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="A random number generator that can be explicitly seeded."><title>SeedableRng in rand_core - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-6b053e98.ttf.woff2,FiraSans-Regular-0fe48ade.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" crossorigin href="../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../static.files/normalize-9960930a.css"><link rel="stylesheet" href="../static.files/rustdoc-42caa33d.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="rand_core" data-themes="" data-resource-suffix="" data-rustdoc-version="1.84.1 (e71f9a9a9 2025-01-27)" data-channel="1.84.1" data-search-js="search-92e6798f.js" data-settings-js="settings-0f613d39.js" ><script src="../static.files/storage-59e33391.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-5f194d8c.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-893ab5e7.css"></noscript><link rel="icon" href="https://www.rust-lang.org/favicon.ico"></head><body class="rustdoc trait"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button><a class="logo-container" href="../rand_core/index.html"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt=""></a></nav><nav class="sidebar"><div class="sidebar-crate"><a class="logo-container" href="../rand_core/index.html"><img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></a><h2><a href="../rand_core/index.html">rand_<wbr>core</a><span class="version">0.6.4</span></h2></div><div class="sidebar-elems"><section id="rustdoc-toc"><h2 class="location"><a href="#">Seedable<wbr>Rng</a></h2><h3><a href="#required-associated-types">Required Associated Types</a></h3><ul class="block"><li><a href="#associatedtype.Seed" title="Seed">Seed</a></li></ul><h3><a href="#required-methods">Required Methods</a></h3><ul class="block"><li><a href="#tymethod.from_seed" title="from_seed">from_seed</a></li></ul><h3><a href="#provided-methods">Provided Methods</a></h3><ul class="block"><li><a href="#method.from_entropy" title="from_entropy">from_entropy</a></li><li><a href="#method.from_rng" title="from_rng">from_rng</a></li><li><a href="#method.seed_from_u64" title="seed_from_u64">seed_from_u64</a></li></ul><h3><a href="#dyn-compatibility">Dyn Compatibility</a></h3><h3><a href="#implementors">Implementors</a></h3></section><div id="rustdoc-modnav"><h2 class="in-crate"><a href="index.html">In crate rand_<wbr>core</a></h2></div></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><span class="rustdoc-breadcrumbs"><a href="index.html">rand_core</a></span><h1>Trait <span class="trait">SeedableRng</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/rand_core/lib.rs.html#246-419">Source</a> </span></div><pre class="rust item-decl"><code>pub trait SeedableRng: <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> {
|
||
type <a href="#associatedtype.Seed" class="associatedtype">Seed</a>: <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> + <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/default/trait.Default.html" title="trait core::default::Default">Default</a> + <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/convert/trait.AsMut.html" title="trait core::convert::AsMut">AsMut</a><[<a class="primitive" href="https://doc.rust-lang.org/1.84.1/std/primitive.u8.html">u8</a>]>;
|
||
|
||
// Required method
|
||
fn <a href="#tymethod.from_seed" class="fn">from_seed</a>(seed: Self::<a class="associatedtype" href="trait.SeedableRng.html#associatedtype.Seed" title="type rand_core::SeedableRng::Seed">Seed</a>) -> Self;
|
||
|
||
// Provided methods
|
||
fn <a href="#method.seed_from_u64" class="fn">seed_from_u64</a>(state: <a class="primitive" href="https://doc.rust-lang.org/1.84.1/std/primitive.u64.html">u64</a>) -> Self { ... }
|
||
<span class="item-spacer"></span> fn <a href="#method.from_rng" class="fn">from_rng</a><R: <a class="trait" href="trait.RngCore.html" title="trait rand_core::RngCore">RngCore</a>>(rng: R) -> <a class="enum" href="https://doc.rust-lang.org/1.84.1/core/result/enum.Result.html" title="enum core::result::Result">Result</a><Self, <a class="struct" href="struct.Error.html" title="struct rand_core::Error">Error</a>> { ... }
|
||
<span class="item-spacer"></span> fn <a href="#method.from_entropy" class="fn">from_entropy</a>() -> Self { ... }
|
||
}</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>A random number generator that can be explicitly seeded.</p>
|
||
<p>This trait encapsulates the low-level functionality common to all
|
||
pseudo-random number generators (PRNGs, or algorithmic generators).</p>
|
||
</div></details><h2 id="required-associated-types" class="section-header">Required Associated Types<a href="#required-associated-types" class="anchor">§</a></h2><div class="methods"><details class="toggle" open><summary><section id="associatedtype.Seed" class="method"><a class="src rightside" href="../src/rand_core/lib.rs.html#292">Source</a><h4 class="code-header">type <a href="#associatedtype.Seed" class="associatedtype">Seed</a>: <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/marker/trait.Sized.html" title="trait core::marker::Sized">Sized</a> + <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/default/trait.Default.html" title="trait core::default::Default">Default</a> + <a class="trait" href="https://doc.rust-lang.org/1.84.1/core/convert/trait.AsMut.html" title="trait core::convert::AsMut">AsMut</a><[<a class="primitive" href="https://doc.rust-lang.org/1.84.1/std/primitive.u8.html">u8</a>]></h4></section></summary><div class="docblock"><p>Seed type, which is restricted to types mutably-dereferenceable as <code>u8</code>
|
||
arrays (we recommend <code>[u8; N]</code> for some <code>N</code>).</p>
|
||
<p>It is recommended to seed PRNGs with a seed of at least circa 100 bits,
|
||
which means an array of <code>[u8; 12]</code> or greater to avoid picking RNGs with
|
||
partially overlapping periods.</p>
|
||
<p>For cryptographic RNG’s a seed of 256 bits is recommended, <code>[u8; 32]</code>.</p>
|
||
<h5 id="implementing-seedablerng-for-rngs-with-large-seeds"><a class="doc-anchor" href="#implementing-seedablerng-for-rngs-with-large-seeds">§</a>Implementing <code>SeedableRng</code> for RNGs with large seeds</h5>
|
||
<p>Note that the required traits <code>core::default::Default</code> and
|
||
<code>core::convert::AsMut<u8></code> are not implemented for large arrays
|
||
<code>[u8; N]</code> with <code>N</code> > 32. To be able to implement the traits required by
|
||
<code>SeedableRng</code> for RNGs with such large seeds, the newtype pattern can be
|
||
used:</p>
|
||
|
||
<div class="example-wrap"><pre class="rust rust-example-rendered"><code><span class="kw">use </span>rand_core::SeedableRng;
|
||
|
||
<span class="kw">const </span>N: usize = <span class="number">64</span>;
|
||
<span class="kw">pub struct </span>MyRngSeed(<span class="kw">pub </span>[u8; N]);
|
||
<span class="kw">pub struct </span>MyRng(MyRngSeed);
|
||
|
||
<span class="kw">impl </span>Default <span class="kw">for </span>MyRngSeed {
|
||
<span class="kw">fn </span>default() -> MyRngSeed {
|
||
MyRngSeed([<span class="number">0</span>; N])
|
||
}
|
||
}
|
||
|
||
<span class="kw">impl </span>AsMut<[u8]> <span class="kw">for </span>MyRngSeed {
|
||
<span class="kw">fn </span>as_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>[u8] {
|
||
<span class="kw-2">&mut </span><span class="self">self</span>.<span class="number">0
|
||
</span>}
|
||
}
|
||
|
||
<span class="kw">impl </span>SeedableRng <span class="kw">for </span>MyRng {
|
||
<span class="kw">type </span>Seed = MyRngSeed;
|
||
|
||
<span class="kw">fn </span>from_seed(seed: MyRngSeed) -> MyRng {
|
||
MyRng(seed)
|
||
}
|
||
}</code></pre></div>
|
||
</div></details></div><h2 id="required-methods" class="section-header">Required Methods<a href="#required-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="tymethod.from_seed" class="method"><a class="src rightside" href="../src/rand_core/lib.rs.html#319">Source</a><h4 class="code-header">fn <a href="#tymethod.from_seed" class="fn">from_seed</a>(seed: Self::<a class="associatedtype" href="trait.SeedableRng.html#associatedtype.Seed" title="type rand_core::SeedableRng::Seed">Seed</a>) -> Self</h4></section></summary><div class="docblock"><p>Create a new PRNG using the given seed.</p>
|
||
<p>PRNG implementations are allowed to assume that bits in the seed are
|
||
well distributed. That means usually that the number of one and zero
|
||
bits are roughly equal, and values like 0, 1 and (size - 1) are unlikely.
|
||
Note that many non-cryptographic PRNGs will show poor quality output
|
||
if this is not adhered to. If you wish to seed from simple numbers, use
|
||
<code>seed_from_u64</code> instead.</p>
|
||
<p>All PRNG implementations should be reproducible unless otherwise noted:
|
||
given a fixed <code>seed</code>, the same sequence of output should be produced
|
||
on all runs, library versions and architectures (e.g. check endianness).
|
||
Any “value-breaking” changes to the generator should require bumping at
|
||
least the minor version and documentation of the change.</p>
|
||
<p>It is not required that this function yield the same state as a
|
||
reference implementation of the PRNG given equivalent seed; if necessary
|
||
another constructor replicating behaviour from a reference
|
||
implementation can be added.</p>
|
||
<p>PRNG implementations should make sure <code>from_seed</code> never panics. In the
|
||
case that some special values (like an all zero seed) are not viable
|
||
seeds it is preferable to map these to alternative constant value(s),
|
||
for example <code>0xBAD5EEDu32</code> or <code>0x0DDB1A5E5BAD5EEDu64</code> (“odd biases? bad
|
||
seed”). This is assuming only a small number of values must be rejected.</p>
|
||
</div></details></div><h2 id="provided-methods" class="section-header">Provided Methods<a href="#provided-methods" class="anchor">§</a></h2><div class="methods"><details class="toggle method-toggle" open><summary><section id="method.seed_from_u64" class="method"><a class="src rightside" href="../src/rand_core/lib.rs.html#335-364">Source</a><h4 class="code-header">fn <a href="#method.seed_from_u64" class="fn">seed_from_u64</a>(state: <a class="primitive" href="https://doc.rust-lang.org/1.84.1/std/primitive.u64.html">u64</a>) -> Self</h4></section></summary><div class="docblock"><p>Create a new PRNG using a <code>u64</code> seed.</p>
|
||
<p>This is a convenience-wrapper around <code>from_seed</code> to allow construction
|
||
of any <code>SeedableRng</code> from a simple <code>u64</code> value. It is designed such that
|
||
low Hamming Weight numbers like 0 and 1 can be used and should still
|
||
result in good, independent seeds to the PRNG which is returned.</p>
|
||
<p>This <strong>is not suitable for cryptography</strong>, as should be clear given that
|
||
the input size is only 64 bits.</p>
|
||
<p>Implementations for PRNGs <em>may</em> provide their own implementations of
|
||
this function, but the default implementation should be good enough for
|
||
all purposes. <em>Changing</em> the implementation of this function should be
|
||
considered a value-breaking change.</p>
|
||
</div></details><details class="toggle method-toggle" open><summary><section id="method.from_rng" class="method"><a class="src rightside" href="../src/rand_core/lib.rs.html#390-394">Source</a><h4 class="code-header">fn <a href="#method.from_rng" class="fn">from_rng</a><R: <a class="trait" href="trait.RngCore.html" title="trait rand_core::RngCore">RngCore</a>>(rng: R) -> <a class="enum" href="https://doc.rust-lang.org/1.84.1/core/result/enum.Result.html" title="enum core::result::Result">Result</a><Self, <a class="struct" href="struct.Error.html" title="struct rand_core::Error">Error</a>></h4></section></summary><div class="docblock"><p>Create a new PRNG seeded from another <code>Rng</code>.</p>
|
||
<p>This may be useful when needing to rapidly seed many PRNGs from a master
|
||
PRNG, and to allow forking of PRNGs. It may be considered deterministic.</p>
|
||
<p>The master PRNG should be at least as high quality as the child PRNGs.
|
||
When seeding non-cryptographic child PRNGs, we recommend using a
|
||
different algorithm for the master PRNG (ideally a CSPRNG) to avoid
|
||
correlations between the child PRNGs. If this is not possible (e.g.
|
||
forking using small non-crypto PRNGs) ensure that your PRNG has a good
|
||
mixing function on the output or consider use of a hash function with
|
||
<code>from_seed</code>.</p>
|
||
<p>Note that seeding <code>XorShiftRng</code> from another <code>XorShiftRng</code> provides an
|
||
extreme example of what can go wrong: the new PRNG will be a clone
|
||
of the parent.</p>
|
||
<p>PRNG implementations are allowed to assume that a good RNG is provided
|
||
for seeding, and that it is cryptographically secure when appropriate.
|
||
As of <code>rand</code> 0.7 / <code>rand_core</code> 0.5, implementations overriding this
|
||
method should ensure the implementation satisfies reproducibility
|
||
(in prior versions this was not required).</p>
|
||
</div></details><details class="toggle method-toggle" open><summary><section id="method.from_entropy" class="method"><a class="src rightside" href="../src/rand_core/lib.rs.html#412-418">Source</a><h4 class="code-header">fn <a href="#method.from_entropy" class="fn">from_entropy</a>() -> Self</h4></section></summary><div class="docblock"><p>Creates a new instance of the RNG seeded via <a href="https://docs.rs/getrandom"><code>getrandom</code></a>.</p>
|
||
<p>This method is the recommended way to construct non-deterministic PRNGs
|
||
since it is convenient and secure.</p>
|
||
<p>In case the overhead of using <a href="https://docs.rs/getrandom"><code>getrandom</code></a> to seed <em>many</em> PRNGs is an
|
||
issue, one may prefer to seed from a local PRNG, e.g.
|
||
<code>from_rng(thread_rng()).unwrap()</code>.</p>
|
||
<h5 id="panics"><a class="doc-anchor" href="#panics">§</a>Panics</h5>
|
||
<p>If <a href="https://docs.rs/getrandom"><code>getrandom</code></a> is unable to provide secure entropy this method will panic.</p>
|
||
</div></details></div><h2 id="dyn-compatibility" class="section-header">Dyn Compatibility<a href="#dyn-compatibility" class="anchor">§</a></h2><div class="dyn-compatibility-info"><p>This trait is <b>not</b> <a href="https://doc.rust-lang.org/1.84.1/reference/items/traits.html#object-safety">dyn compatible</a>.</p><p><i>In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.</i></p></div><h2 id="implementors" class="section-header">Implementors<a href="#implementors" class="anchor">§</a></h2><div id="implementors-list"><details class="toggle implementors-toggle"><summary><section id="impl-SeedableRng-for-BlockRng64%3CR%3E" class="impl"><a class="src rightside" href="../src/rand_core/block.rs.html#412-429">Source</a><a href="#impl-SeedableRng-for-BlockRng64%3CR%3E" class="anchor">§</a><h3 class="code-header">impl<R: <a class="trait" href="block/trait.BlockRngCore.html" title="trait rand_core::block::BlockRngCore">BlockRngCore</a> + <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a>> <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a> for <a class="struct" href="block/struct.BlockRng64.html" title="struct rand_core::block::BlockRng64">BlockRng64</a><R></h3></section></summary><div class="impl-items"><section id="associatedtype.Seed-1" class="associatedtype trait-impl"><a class="src rightside" href="../src/rand_core/block.rs.html#413">Source</a><a href="#associatedtype.Seed-1" class="anchor">§</a><h4 class="code-header">type <a href="#associatedtype.Seed" class="associatedtype">Seed</a> = <R as <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a>>::<a class="associatedtype" href="trait.SeedableRng.html#associatedtype.Seed" title="type rand_core::SeedableRng::Seed">Seed</a></h4></section></div></details><details class="toggle implementors-toggle"><summary><section id="impl-SeedableRng-for-BlockRng%3CR%3E" class="impl"><a class="src rightside" href="../src/rand_core/block.rs.html#243-260">Source</a><a href="#impl-SeedableRng-for-BlockRng%3CR%3E" class="anchor">§</a><h3 class="code-header">impl<R: <a class="trait" href="block/trait.BlockRngCore.html" title="trait rand_core::block::BlockRngCore">BlockRngCore</a> + <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a>> <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a> for <a class="struct" href="block/struct.BlockRng.html" title="struct rand_core::block::BlockRng">BlockRng</a><R></h3></section></summary><div class="impl-items"><section id="associatedtype.Seed-2" class="associatedtype trait-impl"><a class="src rightside" href="../src/rand_core/block.rs.html#244">Source</a><a href="#associatedtype.Seed-2" class="anchor">§</a><h4 class="code-header">type <a href="#associatedtype.Seed" class="associatedtype">Seed</a> = <R as <a class="trait" href="trait.SeedableRng.html" title="trait rand_core::SeedableRng">SeedableRng</a>>::<a class="associatedtype" href="trait.SeedableRng.html#associatedtype.Seed" title="type rand_core::SeedableRng::Seed">Seed</a></h4></section></div></details></div><script src="../trait.impl/rand_core/trait.SeedableRng.js" async></script></section></div></main></body></html> |