| <!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="Source of the Rust file `/root/.cargo/git/checkouts/tokio-377c595163f99a10/dfe252d/tokio/src/util/rand.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>rand.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../tokio/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../tokio/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span>std::cell::Cell; |
| |
| <span class="macro">cfg_rt! </span>{ |
| <span class="kw">use </span>std::sync::Mutex; |
| |
| <span class="doccomment">/// A deterministic generator for seeds (and other generators). |
| /// |
| /// Given the same initial seed, the generator will output the same sequence of seeds. |
| /// |
| /// Since the seed generator will be kept in a runtime handle, we need to wrap `FastRand` |
| /// in a Mutex to make it thread safe. Different to the `FastRand` that we keep in a |
| /// thread local store, the expectation is that seed generation will not need to happen |
| /// very frequently, so the cost of the mutex should be minimal. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>RngSeedGenerator { |
| <span class="doccomment">/// Internal state for the seed generator. We keep it in a Mutex so that we can safely |
| /// use it across multiple threads. |
| </span>state: Mutex<FastRand>, |
| } |
| |
| <span class="kw">impl </span>RngSeedGenerator { |
| <span class="doccomment">/// Returns a new generator from the provided seed. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(seed: RngSeed) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| state: Mutex::new(FastRand::new(seed)), |
| } |
| } |
| |
| <span class="doccomment">/// Returns the next seed in the sequence. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>next_seed(<span class="kw-2">&</span><span class="self">self</span>) -> RngSeed { |
| <span class="kw">let </span>rng = <span class="self">self |
| </span>.state |
| .lock() |
| .expect(<span class="string">"RNG seed generator is internally corrupt"</span>); |
| |
| <span class="kw">let </span>s = rng.fastrand(); |
| <span class="kw">let </span>r = rng.fastrand(); |
| |
| RngSeed::from_pair(s, r) |
| } |
| |
| <span class="doccomment">/// Directly creates a generator using the next seed. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>next_generator(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self </span>{ |
| RngSeedGenerator::new(<span class="self">self</span>.next_seed()) |
| } |
| } |
| } |
| |
| <span class="doccomment">/// A seed for random number generation. |
| /// |
| /// In order to make certain functions within a runtime deterministic, a seed |
| /// can be specified at the time of creation. |
| </span><span class="attribute">#[allow(unreachable_pub)] |
| #[derive(Clone, Debug)] |
| </span><span class="kw">pub struct </span>RngSeed { |
| s: u32, |
| r: u32, |
| } |
| |
| <span class="kw">impl </span>RngSeed { |
| <span class="doccomment">/// Creates a random seed using loom internally. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::from_u64(<span class="kw">crate</span>::loom::rand::seed()) |
| } |
| |
| <span class="macro">cfg_unstable! </span>{ |
| <span class="doccomment">/// Generates a seed from the provided byte slice. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// # use tokio::runtime::RngSeed; |
| /// let seed = RngSeed::from_bytes(b"make me a seed"); |
| /// ``` |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span><span class="kw">pub fn </span>from_bytes(bytes: <span class="kw-2">&</span>[u8]) -> <span class="self">Self </span>{ |
| <span class="kw">use </span>std::{collections::hash_map::DefaultHasher, hash::Hasher}; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>hasher = DefaultHasher::default(); |
| hasher.write(bytes); |
| <span class="self">Self</span>::from_u64(hasher.finish()) |
| } |
| } |
| |
| <span class="kw">fn </span>from_u64(seed: u64) -> <span class="self">Self </span>{ |
| <span class="kw">let </span>one = (seed >> <span class="number">32</span>) <span class="kw">as </span>u32; |
| <span class="kw">let </span><span class="kw-2">mut </span>two = seed <span class="kw">as </span>u32; |
| |
| <span class="kw">if </span>two == <span class="number">0 </span>{ |
| <span class="comment">// This value cannot be zero |
| </span>two = <span class="number">1</span>; |
| } |
| |
| <span class="self">Self</span>::from_pair(one, two) |
| } |
| |
| <span class="kw">fn </span>from_pair(s: u32, r: u32) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ s, r } |
| } |
| } |
| <span class="doccomment">/// Fast random number generate. |
| /// |
| /// Implement xorshift64+: 2 32-bit xorshift sequences added together. |
| /// Shift triplet `[17,7,16]` was calculated as indicated in Marsaglia's |
| /// Xorshift paper: <https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf> |
| /// This generator passes the SmallCrush suite, part of TestU01 framework: |
| /// <http://simul.iro.umontreal.ca/testu01/tu01.html> |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>FastRand { |
| one: Cell<u32>, |
| two: Cell<u32>, |
| } |
| |
| <span class="kw">impl </span>FastRand { |
| <span class="doccomment">/// Initializes a new, thread-local, fast random number generator. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(seed: RngSeed) -> FastRand { |
| FastRand { |
| one: Cell::new(seed.s), |
| two: Cell::new(seed.r), |
| } |
| } |
| |
| <span class="doccomment">/// Replaces the state of the random number generator with the provided seed, returning |
| /// the seed that represents the previous state of the random number generator. |
| /// |
| /// The random number generator will become equivalent to one created with |
| /// the same seed. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>replace_seed(<span class="kw-2">&</span><span class="self">self</span>, seed: RngSeed) -> RngSeed { |
| <span class="kw">let </span>old_seed = RngSeed::from_pair(<span class="self">self</span>.one.get(), <span class="self">self</span>.two.get()); |
| |
| <span class="self">self</span>.one.replace(seed.s); |
| <span class="self">self</span>.two.replace(seed.r); |
| |
| old_seed |
| } |
| |
| <span class="attribute">#[cfg(any(feature = <span class="string">"macros"</span>, feature = <span class="string">"rt-multi-thread"</span>))] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>fastrand_n(<span class="kw-2">&</span><span class="self">self</span>, n: u32) -> u32 { |
| <span class="comment">// This is similar to fastrand() % n, but faster. |
| // See https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/ |
| </span><span class="kw">let </span>mul = (<span class="self">self</span>.fastrand() <span class="kw">as </span>u64).wrapping_mul(n <span class="kw">as </span>u64); |
| (mul >> <span class="number">32</span>) <span class="kw">as </span>u32 |
| } |
| |
| <span class="kw">fn </span>fastrand(<span class="kw-2">&</span><span class="self">self</span>) -> u32 { |
| <span class="kw">let </span><span class="kw-2">mut </span>s1 = <span class="self">self</span>.one.get(); |
| <span class="kw">let </span>s0 = <span class="self">self</span>.two.get(); |
| |
| s1 ^= s1 << <span class="number">17</span>; |
| s1 = s1 ^ s0 ^ s1 >> <span class="number">7 </span>^ s0 >> <span class="number">16</span>; |
| |
| <span class="self">self</span>.one.set(s0); |
| <span class="self">self</span>.two.set(s1); |
| |
| s0.wrapping_add(s1) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |