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| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| </span><span class="attribute">#[cfg(feature=<span class="string">"serde1"</span>)] </span><span class="kw">use </span>serde::{Serialize, Deserialize}; |
| <span class="kw">use </span>rand_core::impls::fill_bytes_via_next; |
| <span class="kw">use </span>rand_core::le::read_u64_into; |
| <span class="kw">use </span>rand_core::{SeedableRng, RngCore, Error}; |
| |
| <span class="doccomment">/// A xoshiro256++ random number generator. |
| /// |
| /// The xoshiro256++ algorithm is not suitable for cryptographic purposes, but |
| /// is very fast and has excellent statistical properties. |
| /// |
| /// The algorithm used here is translated from [the `xoshiro256plusplus.c` |
| /// reference source code](http://xoshiro.di.unimi.it/xoshiro256plusplus.c) by |
| /// David Blackman and Sebastiano Vigna. |
| </span><span class="attribute">#[derive(Debug, Clone, PartialEq, Eq)] |
| #[cfg_attr(feature=<span class="string">"serde1"</span>, derive(Serialize, Deserialize))] |
| </span><span class="kw">pub struct </span>Xoshiro256PlusPlus { |
| s: [u64; <span class="number">4</span>], |
| } |
| |
| <span class="kw">impl </span>SeedableRng <span class="kw">for </span>Xoshiro256PlusPlus { |
| <span class="kw">type </span>Seed = [u8; <span class="number">32</span>]; |
| |
| <span class="doccomment">/// Create a new `Xoshiro256PlusPlus`. If `seed` is entirely 0, it will be |
| /// mapped to a different seed. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">fn </span>from_seed(seed: [u8; <span class="number">32</span>]) -> Xoshiro256PlusPlus { |
| <span class="kw">if </span>seed.iter().all(|<span class="kw-2">&</span>x| x == <span class="number">0</span>) { |
| <span class="kw">return </span><span class="self">Self</span>::seed_from_u64(<span class="number">0</span>); |
| } |
| <span class="kw">let </span><span class="kw-2">mut </span>state = [<span class="number">0</span>; <span class="number">4</span>]; |
| read_u64_into(<span class="kw-2">&</span>seed, <span class="kw-2">&mut </span>state); |
| Xoshiro256PlusPlus { s: state } |
| } |
| |
| <span class="doccomment">/// Create a new `Xoshiro256PlusPlus` from a `u64` seed. |
| /// |
| /// This uses the SplitMix64 generator internally. |
| </span><span class="kw">fn </span>seed_from_u64(<span class="kw-2">mut </span>state: u64) -> <span class="self">Self </span>{ |
| <span class="kw">const </span>PHI: u64 = <span class="number">0x9e3779b97f4a7c15</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>seed = <span class="self">Self</span>::Seed::default(); |
| <span class="kw">for </span>chunk <span class="kw">in </span>seed.as_mut().chunks_mut(<span class="number">8</span>) { |
| state = state.wrapping_add(PHI); |
| <span class="kw">let </span><span class="kw-2">mut </span>z = state; |
| z = (z ^ (z >> <span class="number">30</span>)).wrapping_mul(<span class="number">0xbf58476d1ce4e5b9</span>); |
| z = (z ^ (z >> <span class="number">27</span>)).wrapping_mul(<span class="number">0x94d049bb133111eb</span>); |
| z = z ^ (z >> <span class="number">31</span>); |
| chunk.copy_from_slice(<span class="kw-2">&</span>z.to_le_bytes()); |
| } |
| <span class="self">Self</span>::from_seed(seed) |
| } |
| } |
| |
| <span class="kw">impl </span>RngCore <span class="kw">for </span>Xoshiro256PlusPlus { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>next_u32(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| <span class="comment">// The lowest bits have some linear dependencies, so we use the |
| // upper bits instead. |
| </span>(<span class="self">self</span>.next_u64() >> <span class="number">32</span>) <span class="kw">as </span>u32 |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>next_u64(<span class="kw-2">&mut </span><span class="self">self</span>) -> u64 { |
| <span class="kw">let </span>result_plusplus = <span class="self">self</span>.s[<span class="number">0</span>] |
| .wrapping_add(<span class="self">self</span>.s[<span class="number">3</span>]) |
| .rotate_left(<span class="number">23</span>) |
| .wrapping_add(<span class="self">self</span>.s[<span class="number">0</span>]); |
| |
| <span class="kw">let </span>t = <span class="self">self</span>.s[<span class="number">1</span>] << <span class="number">17</span>; |
| |
| <span class="self">self</span>.s[<span class="number">2</span>] ^= <span class="self">self</span>.s[<span class="number">0</span>]; |
| <span class="self">self</span>.s[<span class="number">3</span>] ^= <span class="self">self</span>.s[<span class="number">1</span>]; |
| <span class="self">self</span>.s[<span class="number">1</span>] ^= <span class="self">self</span>.s[<span class="number">2</span>]; |
| <span class="self">self</span>.s[<span class="number">0</span>] ^= <span class="self">self</span>.s[<span class="number">3</span>]; |
| |
| <span class="self">self</span>.s[<span class="number">2</span>] ^= t; |
| |
| <span class="self">self</span>.s[<span class="number">3</span>] = <span class="self">self</span>.s[<span class="number">3</span>].rotate_left(<span class="number">45</span>); |
| |
| result_plusplus |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>fill_bytes(<span class="kw-2">&mut </span><span class="self">self</span>, dest: <span class="kw-2">&mut </span>[u8]) { |
| fill_bytes_via_next(<span class="self">self</span>, dest); |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>try_fill_bytes(<span class="kw-2">&mut </span><span class="self">self</span>, dest: <span class="kw-2">&mut </span>[u8]) -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="self">self</span>.fill_bytes(dest); |
| <span class="prelude-val">Ok</span>(()) |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>reference() { |
| <span class="kw">let </span><span class="kw-2">mut </span>rng = Xoshiro256PlusPlus::from_seed( |
| [<span class="number">1</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">2</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, |
| <span class="number">3</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">4</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>, <span class="number">0</span>]); |
| <span class="comment">// These values were produced with the reference implementation: |
| // http://xoshiro.di.unimi.it/xoshiro256plusplus.c |
| </span><span class="kw">let </span>expected = [ |
| <span class="number">41943041</span>, <span class="number">58720359</span>, <span class="number">3588806011781223</span>, <span class="number">3591011842654386</span>, |
| <span class="number">9228616714210784205</span>, <span class="number">9973669472204895162</span>, <span class="number">14011001112246962877</span>, |
| <span class="number">12406186145184390807</span>, <span class="number">15849039046786891736</span>, <span class="number">10450023813501588000</span>, |
| ]; |
| <span class="kw">for </span><span class="kw-2">&</span>e <span class="kw">in </span><span class="kw-2">&</span>expected { |
| <span class="macro">assert_eq!</span>(rng.next_u64(), e); |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="rand" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
