| <!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/registry/src/github.com-1ecc6299db9ec823/rand_core-0.6.4/src/lib.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lib.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="icon" href="https://www.rust-lang.org/favicon.ico"></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="../../rand_core/index.html"><div class="logo-container"> |
| <img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../rand_core/index.html"> |
| <img src="https://www.rust-lang.org/logos/rust-logo-128x128-blk.png" 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> |
| <span id="2">2</span> |
| <span id="3">3</span> |
| <span id="4">4</span> |
| <span id="5">5</span> |
| <span id="6">6</span> |
| <span id="7">7</span> |
| <span id="8">8</span> |
| <span id="9">9</span> |
| <span id="10">10</span> |
| <span id="11">11</span> |
| <span id="12">12</span> |
| <span id="13">13</span> |
| <span id="14">14</span> |
| <span id="15">15</span> |
| <span id="16">16</span> |
| <span id="17">17</span> |
| <span id="18">18</span> |
| <span id="19">19</span> |
| <span id="20">20</span> |
| <span id="21">21</span> |
| <span id="22">22</span> |
| <span id="23">23</span> |
| <span id="24">24</span> |
| <span id="25">25</span> |
| <span id="26">26</span> |
| <span id="27">27</span> |
| <span id="28">28</span> |
| <span id="29">29</span> |
| <span id="30">30</span> |
| <span id="31">31</span> |
| <span id="32">32</span> |
| <span id="33">33</span> |
| <span id="34">34</span> |
| <span id="35">35</span> |
| <span id="36">36</span> |
| <span id="37">37</span> |
| <span id="38">38</span> |
| <span id="39">39</span> |
| <span id="40">40</span> |
| <span id="41">41</span> |
| <span id="42">42</span> |
| <span id="43">43</span> |
| <span id="44">44</span> |
| <span id="45">45</span> |
| <span id="46">46</span> |
| <span id="47">47</span> |
| <span id="48">48</span> |
| <span id="49">49</span> |
| <span id="50">50</span> |
| <span id="51">51</span> |
| <span id="52">52</span> |
| <span id="53">53</span> |
| <span id="54">54</span> |
| <span id="55">55</span> |
| <span id="56">56</span> |
| <span id="57">57</span> |
| <span id="58">58</span> |
| <span id="59">59</span> |
| <span id="60">60</span> |
| <span id="61">61</span> |
| <span id="62">62</span> |
| <span id="63">63</span> |
| <span id="64">64</span> |
| <span id="65">65</span> |
| <span id="66">66</span> |
| <span id="67">67</span> |
| <span id="68">68</span> |
| <span id="69">69</span> |
| <span id="70">70</span> |
| <span id="71">71</span> |
| <span id="72">72</span> |
| <span id="73">73</span> |
| <span id="74">74</span> |
| <span id="75">75</span> |
| <span id="76">76</span> |
| <span id="77">77</span> |
| <span id="78">78</span> |
| <span id="79">79</span> |
| <span id="80">80</span> |
| <span id="81">81</span> |
| <span id="82">82</span> |
| <span id="83">83</span> |
| <span id="84">84</span> |
| <span id="85">85</span> |
| <span id="86">86</span> |
| <span id="87">87</span> |
| <span id="88">88</span> |
| <span id="89">89</span> |
| <span id="90">90</span> |
| <span id="91">91</span> |
| <span id="92">92</span> |
| <span id="93">93</span> |
| <span id="94">94</span> |
| <span id="95">95</span> |
| <span id="96">96</span> |
| <span id="97">97</span> |
| <span id="98">98</span> |
| <span id="99">99</span> |
| <span id="100">100</span> |
| <span id="101">101</span> |
| <span id="102">102</span> |
| <span id="103">103</span> |
| <span id="104">104</span> |
| <span id="105">105</span> |
| <span id="106">106</span> |
| <span id="107">107</span> |
| <span id="108">108</span> |
| <span id="109">109</span> |
| <span id="110">110</span> |
| <span id="111">111</span> |
| <span id="112">112</span> |
| <span id="113">113</span> |
| <span id="114">114</span> |
| <span id="115">115</span> |
| <span id="116">116</span> |
| <span id="117">117</span> |
| <span id="118">118</span> |
| <span id="119">119</span> |
| <span id="120">120</span> |
| <span id="121">121</span> |
| <span id="122">122</span> |
| <span id="123">123</span> |
| <span id="124">124</span> |
| <span id="125">125</span> |
| <span id="126">126</span> |
| <span id="127">127</span> |
| <span id="128">128</span> |
| <span id="129">129</span> |
| <span id="130">130</span> |
| <span id="131">131</span> |
| <span id="132">132</span> |
| <span id="133">133</span> |
| <span id="134">134</span> |
| <span id="135">135</span> |
| <span id="136">136</span> |
| <span id="137">137</span> |
| <span id="138">138</span> |
| <span id="139">139</span> |
| <span id="140">140</span> |
| <span id="141">141</span> |
| <span id="142">142</span> |
| <span id="143">143</span> |
| <span id="144">144</span> |
| <span id="145">145</span> |
| <span id="146">146</span> |
| <span id="147">147</span> |
| <span id="148">148</span> |
| <span id="149">149</span> |
| <span id="150">150</span> |
| <span id="151">151</span> |
| <span id="152">152</span> |
| <span id="153">153</span> |
| <span id="154">154</span> |
| <span id="155">155</span> |
| <span id="156">156</span> |
| <span id="157">157</span> |
| <span id="158">158</span> |
| <span id="159">159</span> |
| <span id="160">160</span> |
| <span id="161">161</span> |
| <span id="162">162</span> |
| <span id="163">163</span> |
| <span id="164">164</span> |
| <span id="165">165</span> |
| <span id="166">166</span> |
| <span id="167">167</span> |
| <span id="168">168</span> |
| <span id="169">169</span> |
| <span id="170">170</span> |
| <span id="171">171</span> |
| <span id="172">172</span> |
| <span id="173">173</span> |
| <span id="174">174</span> |
| <span id="175">175</span> |
| <span id="176">176</span> |
| <span id="177">177</span> |
| <span id="178">178</span> |
| <span id="179">179</span> |
| <span id="180">180</span> |
| <span id="181">181</span> |
| <span id="182">182</span> |
| <span id="183">183</span> |
| <span id="184">184</span> |
| <span id="185">185</span> |
| <span id="186">186</span> |
| <span id="187">187</span> |
| <span id="188">188</span> |
| <span id="189">189</span> |
| <span id="190">190</span> |
| <span id="191">191</span> |
| <span id="192">192</span> |
| <span id="193">193</span> |
| <span id="194">194</span> |
| <span id="195">195</span> |
| <span id="196">196</span> |
| <span id="197">197</span> |
| <span id="198">198</span> |
| <span id="199">199</span> |
| <span id="200">200</span> |
| <span id="201">201</span> |
| <span id="202">202</span> |
| <span id="203">203</span> |
| <span id="204">204</span> |
| <span id="205">205</span> |
| <span id="206">206</span> |
| <span id="207">207</span> |
| <span id="208">208</span> |
| <span id="209">209</span> |
| <span id="210">210</span> |
| <span id="211">211</span> |
| <span id="212">212</span> |
| <span id="213">213</span> |
| <span id="214">214</span> |
| <span id="215">215</span> |
| <span id="216">216</span> |
| <span id="217">217</span> |
| <span id="218">218</span> |
| <span id="219">219</span> |
| <span id="220">220</span> |
| <span id="221">221</span> |
| <span id="222">222</span> |
| <span id="223">223</span> |
| <span id="224">224</span> |
| <span id="225">225</span> |
| <span id="226">226</span> |
| <span id="227">227</span> |
| <span id="228">228</span> |
| <span id="229">229</span> |
| <span id="230">230</span> |
| <span id="231">231</span> |
| <span id="232">232</span> |
| <span id="233">233</span> |
| <span id="234">234</span> |
| <span id="235">235</span> |
| <span id="236">236</span> |
| <span id="237">237</span> |
| <span id="238">238</span> |
| <span id="239">239</span> |
| <span id="240">240</span> |
| <span id="241">241</span> |
| <span id="242">242</span> |
| <span id="243">243</span> |
| <span id="244">244</span> |
| <span id="245">245</span> |
| <span id="246">246</span> |
| <span id="247">247</span> |
| <span id="248">248</span> |
| <span id="249">249</span> |
| <span id="250">250</span> |
| <span id="251">251</span> |
| <span id="252">252</span> |
| <span id="253">253</span> |
| <span id="254">254</span> |
| <span id="255">255</span> |
| <span id="256">256</span> |
| <span id="257">257</span> |
| <span id="258">258</span> |
| <span id="259">259</span> |
| <span id="260">260</span> |
| <span id="261">261</span> |
| <span id="262">262</span> |
| <span id="263">263</span> |
| <span id="264">264</span> |
| <span id="265">265</span> |
| <span id="266">266</span> |
| <span id="267">267</span> |
| <span id="268">268</span> |
| <span id="269">269</span> |
| <span id="270">270</span> |
| <span id="271">271</span> |
| <span id="272">272</span> |
| <span id="273">273</span> |
| <span id="274">274</span> |
| <span id="275">275</span> |
| <span id="276">276</span> |
| <span id="277">277</span> |
| <span id="278">278</span> |
| <span id="279">279</span> |
| <span id="280">280</span> |
| <span id="281">281</span> |
| <span id="282">282</span> |
| <span id="283">283</span> |
| <span id="284">284</span> |
| <span id="285">285</span> |
| <span id="286">286</span> |
| <span id="287">287</span> |
| <span id="288">288</span> |
| <span id="289">289</span> |
| <span id="290">290</span> |
| <span id="291">291</span> |
| <span id="292">292</span> |
| <span id="293">293</span> |
| <span id="294">294</span> |
| <span id="295">295</span> |
| <span id="296">296</span> |
| <span id="297">297</span> |
| <span id="298">298</span> |
| <span id="299">299</span> |
| <span id="300">300</span> |
| <span id="301">301</span> |
| <span id="302">302</span> |
| <span id="303">303</span> |
| <span id="304">304</span> |
| <span id="305">305</span> |
| <span id="306">306</span> |
| <span id="307">307</span> |
| <span id="308">308</span> |
| <span id="309">309</span> |
| <span id="310">310</span> |
| <span id="311">311</span> |
| <span id="312">312</span> |
| <span id="313">313</span> |
| <span id="314">314</span> |
| <span id="315">315</span> |
| <span id="316">316</span> |
| <span id="317">317</span> |
| <span id="318">318</span> |
| <span id="319">319</span> |
| <span id="320">320</span> |
| <span id="321">321</span> |
| <span id="322">322</span> |
| <span id="323">323</span> |
| <span id="324">324</span> |
| <span id="325">325</span> |
| <span id="326">326</span> |
| <span id="327">327</span> |
| <span id="328">328</span> |
| <span id="329">329</span> |
| <span id="330">330</span> |
| <span id="331">331</span> |
| <span id="332">332</span> |
| <span id="333">333</span> |
| <span id="334">334</span> |
| <span id="335">335</span> |
| <span id="336">336</span> |
| <span id="337">337</span> |
| <span id="338">338</span> |
| <span id="339">339</span> |
| <span id="340">340</span> |
| <span id="341">341</span> |
| <span id="342">342</span> |
| <span id="343">343</span> |
| <span id="344">344</span> |
| <span id="345">345</span> |
| <span id="346">346</span> |
| <span id="347">347</span> |
| <span id="348">348</span> |
| <span id="349">349</span> |
| <span id="350">350</span> |
| <span id="351">351</span> |
| <span id="352">352</span> |
| <span id="353">353</span> |
| <span id="354">354</span> |
| <span id="355">355</span> |
| <span id="356">356</span> |
| <span id="357">357</span> |
| <span id="358">358</span> |
| <span id="359">359</span> |
| <span id="360">360</span> |
| <span id="361">361</span> |
| <span id="362">362</span> |
| <span id="363">363</span> |
| <span id="364">364</span> |
| <span id="365">365</span> |
| <span id="366">366</span> |
| <span id="367">367</span> |
| <span id="368">368</span> |
| <span id="369">369</span> |
| <span id="370">370</span> |
| <span id="371">371</span> |
| <span id="372">372</span> |
| <span id="373">373</span> |
| <span id="374">374</span> |
| <span id="375">375</span> |
| <span id="376">376</span> |
| <span id="377">377</span> |
| <span id="378">378</span> |
| <span id="379">379</span> |
| <span id="380">380</span> |
| <span id="381">381</span> |
| <span id="382">382</span> |
| <span id="383">383</span> |
| <span id="384">384</span> |
| <span id="385">385</span> |
| <span id="386">386</span> |
| <span id="387">387</span> |
| <span id="388">388</span> |
| <span id="389">389</span> |
| <span id="390">390</span> |
| <span id="391">391</span> |
| <span id="392">392</span> |
| <span id="393">393</span> |
| <span id="394">394</span> |
| <span id="395">395</span> |
| <span id="396">396</span> |
| <span id="397">397</span> |
| <span id="398">398</span> |
| <span id="399">399</span> |
| <span id="400">400</span> |
| <span id="401">401</span> |
| <span id="402">402</span> |
| <span id="403">403</span> |
| <span id="404">404</span> |
| <span id="405">405</span> |
| <span id="406">406</span> |
| <span id="407">407</span> |
| <span id="408">408</span> |
| <span id="409">409</span> |
| <span id="410">410</span> |
| <span id="411">411</span> |
| <span id="412">412</span> |
| <span id="413">413</span> |
| <span id="414">414</span> |
| <span id="415">415</span> |
| <span id="416">416</span> |
| <span id="417">417</span> |
| <span id="418">418</span> |
| <span id="419">419</span> |
| <span id="420">420</span> |
| <span id="421">421</span> |
| <span id="422">422</span> |
| <span id="423">423</span> |
| <span id="424">424</span> |
| <span id="425">425</span> |
| <span id="426">426</span> |
| <span id="427">427</span> |
| <span id="428">428</span> |
| <span id="429">429</span> |
| <span id="430">430</span> |
| <span id="431">431</span> |
| <span id="432">432</span> |
| <span id="433">433</span> |
| <span id="434">434</span> |
| <span id="435">435</span> |
| <span id="436">436</span> |
| <span id="437">437</span> |
| <span id="438">438</span> |
| <span id="439">439</span> |
| <span id="440">440</span> |
| <span id="441">441</span> |
| <span id="442">442</span> |
| <span id="443">443</span> |
| <span id="444">444</span> |
| <span id="445">445</span> |
| <span id="446">446</span> |
| <span id="447">447</span> |
| <span id="448">448</span> |
| <span id="449">449</span> |
| <span id="450">450</span> |
| <span id="451">451</span> |
| <span id="452">452</span> |
| <span id="453">453</span> |
| <span id="454">454</span> |
| <span id="455">455</span> |
| <span id="456">456</span> |
| <span id="457">457</span> |
| <span id="458">458</span> |
| <span id="459">459</span> |
| <span id="460">460</span> |
| <span id="461">461</span> |
| <span id="462">462</span> |
| <span id="463">463</span> |
| <span id="464">464</span> |
| <span id="465">465</span> |
| <span id="466">466</span> |
| <span id="467">467</span> |
| <span id="468">468</span> |
| <span id="469">469</span> |
| <span id="470">470</span> |
| <span id="471">471</span> |
| <span id="472">472</span> |
| <span id="473">473</span> |
| <span id="474">474</span> |
| <span id="475">475</span> |
| <span id="476">476</span> |
| <span id="477">477</span> |
| <span id="478">478</span> |
| <span id="479">479</span> |
| <span id="480">480</span> |
| <span id="481">481</span> |
| <span id="482">482</span> |
| <span id="483">483</span> |
| <span id="484">484</span> |
| <span id="485">485</span> |
| <span id="486">486</span> |
| <span id="487">487</span> |
| <span id="488">488</span> |
| <span id="489">489</span> |
| <span id="490">490</span> |
| <span id="491">491</span> |
| <span id="492">492</span> |
| <span id="493">493</span> |
| <span id="494">494</span> |
| <span id="495">495</span> |
| <span id="496">496</span> |
| <span id="497">497</span> |
| <span id="498">498</span> |
| <span id="499">499</span> |
| <span id="500">500</span> |
| <span id="501">501</span> |
| <span id="502">502</span> |
| <span id="503">503</span> |
| <span id="504">504</span> |
| <span id="505">505</span> |
| <span id="506">506</span> |
| <span id="507">507</span> |
| <span id="508">508</span> |
| <span id="509">509</span> |
| <span id="510">510</span> |
| <span id="511">511</span> |
| <span id="512">512</span> |
| <span id="513">513</span> |
| <span id="514">514</span> |
| <span id="515">515</span> |
| <span id="516">516</span> |
| <span id="517">517</span> |
| <span id="518">518</span> |
| <span id="519">519</span> |
| <span id="520">520</span> |
| <span id="521">521</span> |
| <span id="522">522</span> |
| <span id="523">523</span> |
| <span id="524">524</span> |
| <span id="525">525</span> |
| <span id="526">526</span> |
| <span id="527">527</span> |
| <span id="528">528</span> |
| <span id="529">529</span> |
| <span id="530">530</span> |
| <span id="531">531</span> |
| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // Copyright 2017-2018 The Rust Project Developers. |
| // |
| // 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="doccomment">//! Random number generation traits |
| //! |
| //! This crate is mainly of interest to crates publishing implementations of |
| //! [`RngCore`]. Other users are encouraged to use the [`rand`] crate instead |
| //! which re-exports the main traits and error types. |
| //! |
| //! [`RngCore`] is the core trait implemented by algorithmic pseudo-random number |
| //! generators and external random-number sources. |
| //! |
| //! [`SeedableRng`] is an extension trait for construction from fixed seeds and |
| //! other random number generators. |
| //! |
| //! [`Error`] is provided for error-handling. It is safe to use in `no_std` |
| //! environments. |
| //! |
| //! The [`impls`] and [`le`] sub-modules include a few small functions to assist |
| //! implementation of [`RngCore`]. |
| //! |
| //! [`rand`]: https://docs.rs/rand |
| |
| </span><span class="attribute">#![doc( |
| html_logo_url = <span class="string">"https://www.rust-lang.org/logos/rust-logo-128x128-blk.png"</span>, |
| html_favicon_url = <span class="string">"https://www.rust-lang.org/favicon.ico"</span>, |
| html_root_url = <span class="string">"https://rust-random.github.io/rand/" |
| </span>)] |
| #![deny(missing_docs)] |
| #![deny(missing_debug_implementations)] |
| #![doc(test(attr(allow(unused_variables), deny(warnings))))] |
| #![cfg_attr(doc_cfg, feature(doc_cfg))] |
| #![no_std] |
| |
| </span><span class="kw">use </span>core::convert::AsMut; |
| <span class="kw">use </span>core::default::Default; |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] </span><span class="kw">extern crate </span>std; |
| <span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] </span><span class="kw">extern crate </span>alloc; |
| <span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] </span><span class="kw">use </span>alloc::boxed::Box; |
| |
| <span class="kw">pub use </span>error::Error; |
| <span class="attribute">#[cfg(feature = <span class="string">"getrandom"</span>)] </span><span class="kw">pub use </span>os::OsRng; |
| |
| |
| <span class="kw">pub mod </span>block; |
| <span class="kw">mod </span>error; |
| <span class="kw">pub mod </span>impls; |
| <span class="kw">pub mod </span>le; |
| <span class="attribute">#[cfg(feature = <span class="string">"getrandom"</span>)] </span><span class="kw">mod </span>os; |
| |
| |
| <span class="doccomment">/// The core of a random number generator. |
| /// |
| /// This trait encapsulates the low-level functionality common to all |
| /// generators, and is the "back end", to be implemented by generators. |
| /// End users should normally use the `Rng` trait from the [`rand`] crate, |
| /// which is automatically implemented for every type implementing `RngCore`. |
| /// |
| /// Three different methods for generating random data are provided since the |
| /// optimal implementation of each is dependent on the type of generator. There |
| /// is no required relationship between the output of each; e.g. many |
| /// implementations of [`fill_bytes`] consume a whole number of `u32` or `u64` |
| /// values and drop any remaining unused bytes. The same can happen with the |
| /// [`next_u32`] and [`next_u64`] methods, implementations may discard some |
| /// random bits for efficiency. |
| /// |
| /// The [`try_fill_bytes`] method is a variant of [`fill_bytes`] allowing error |
| /// handling; it is not deemed sufficiently useful to add equivalents for |
| /// [`next_u32`] or [`next_u64`] since the latter methods are almost always used |
| /// with algorithmic generators (PRNGs), which are normally infallible. |
| /// |
| /// Implementers should produce bits uniformly. Pathological RNGs (e.g. always |
| /// returning the same value, or never setting certain bits) can break rejection |
| /// sampling used by random distributions, and also break other RNGs when |
| /// seeding them via [`SeedableRng::from_rng`]. |
| /// |
| /// Algorithmic generators implementing [`SeedableRng`] should normally have |
| /// *portable, reproducible* output, i.e. fix Endianness when converting values |
| /// to avoid platform differences, and avoid making any changes which affect |
| /// output (except by communicating that the release has breaking changes). |
| /// |
| /// Typically an RNG will implement only one of the methods available |
| /// in this trait directly, then use the helper functions from the |
| /// [`impls`] module to implement the other methods. |
| /// |
| /// It is recommended that implementations also implement: |
| /// |
| /// - `Debug` with a custom implementation which *does not* print any internal |
| /// state (at least, [`CryptoRng`]s should not risk leaking state through |
| /// `Debug`). |
| /// - `Serialize` and `Deserialize` (from Serde), preferably making Serde |
| /// support optional at the crate level in PRNG libs. |
| /// - `Clone`, if possible. |
| /// - *never* implement `Copy` (accidental copies may cause repeated values). |
| /// - *do not* implement `Default` for pseudorandom generators, but instead |
| /// implement [`SeedableRng`], to guide users towards proper seeding. |
| /// External / hardware RNGs can choose to implement `Default`. |
| /// - `Eq` and `PartialEq` could be implemented, but are probably not useful. |
| /// |
| /// # Example |
| /// |
| /// A simple example, obviously not generating very *random* output: |
| /// |
| /// ``` |
| /// #![allow(dead_code)] |
| /// use rand_core::{RngCore, Error, impls}; |
| /// |
| /// struct CountingRng(u64); |
| /// |
| /// impl RngCore for CountingRng { |
| /// fn next_u32(&mut self) -> u32 { |
| /// self.next_u64() as u32 |
| /// } |
| /// |
| /// fn next_u64(&mut self) -> u64 { |
| /// self.0 += 1; |
| /// self.0 |
| /// } |
| /// |
| /// fn fill_bytes(&mut self, dest: &mut [u8]) { |
| /// impls::fill_bytes_via_next(self, dest) |
| /// } |
| /// |
| /// fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { |
| /// Ok(self.fill_bytes(dest)) |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// [`rand`]: https://docs.rs/rand |
| /// [`try_fill_bytes`]: RngCore::try_fill_bytes |
| /// [`fill_bytes`]: RngCore::fill_bytes |
| /// [`next_u32`]: RngCore::next_u32 |
| /// [`next_u64`]: RngCore::next_u64 |
| </span><span class="kw">pub trait </span>RngCore { |
| <span class="doccomment">/// Return the next random `u32`. |
| /// |
| /// RNGs must implement at least one method from this trait directly. In |
| /// the case this method is not implemented directly, it can be implemented |
| /// using `self.next_u64() as u32` or via [`impls::next_u32_via_fill`]. |
| </span><span class="kw">fn </span>next_u32(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32; |
| |
| <span class="doccomment">/// Return the next random `u64`. |
| /// |
| /// RNGs must implement at least one method from this trait directly. In |
| /// the case this method is not implemented directly, it can be implemented |
| /// via [`impls::next_u64_via_u32`] or via [`impls::next_u64_via_fill`]. |
| </span><span class="kw">fn </span>next_u64(<span class="kw-2">&mut </span><span class="self">self</span>) -> u64; |
| |
| <span class="doccomment">/// Fill `dest` with random data. |
| /// |
| /// RNGs must implement at least one method from this trait directly. In |
| /// the case this method is not implemented directly, it can be implemented |
| /// via [`impls::fill_bytes_via_next`] or |
| /// via [`RngCore::try_fill_bytes`]; if this generator can |
| /// fail the implementation must choose how best to handle errors here |
| /// (e.g. panic with a descriptive message or log a warning and retry a few |
| /// times). |
| /// |
| /// This method should guarantee that `dest` is entirely filled |
| /// with new data, and may panic if this is impossible |
| /// (e.g. reading past the end of a file that is being used as the |
| /// source of randomness). |
| </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]); |
| |
| <span class="doccomment">/// Fill `dest` entirely with random data. |
| /// |
| /// This is the only method which allows an RNG to report errors while |
| /// generating random data thus making this the primary method implemented |
| /// by external (true) RNGs (e.g. `OsRng`) which can fail. It may be used |
| /// directly to generate keys and to seed (infallible) PRNGs. |
| /// |
| /// Other than error handling, this method is identical to [`RngCore::fill_bytes`]; |
| /// thus this may be implemented using `Ok(self.fill_bytes(dest))` or |
| /// `fill_bytes` may be implemented with |
| /// `self.try_fill_bytes(dest).unwrap()` or more specific error handling. |
| </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="doccomment">/// A marker trait used to indicate that an [`RngCore`] or [`BlockRngCore`] |
| /// implementation is supposed to be cryptographically secure. |
| /// |
| /// *Cryptographically secure generators*, also known as *CSPRNGs*, should |
| /// satisfy an additional properties over other generators: given the first |
| /// *k* bits of an algorithm's output |
| /// sequence, it should not be possible using polynomial-time algorithms to |
| /// predict the next bit with probability significantly greater than 50%. |
| /// |
| /// Some generators may satisfy an additional property, however this is not |
| /// required by this trait: if the CSPRNG's state is revealed, it should not be |
| /// computationally-feasible to reconstruct output prior to this. Some other |
| /// generators allow backwards-computation and are considered *reversible*. |
| /// |
| /// Note that this trait is provided for guidance only and cannot guarantee |
| /// suitability for cryptographic applications. In general it should only be |
| /// implemented for well-reviewed code implementing well-regarded algorithms. |
| /// |
| /// Note also that use of a `CryptoRng` does not protect against other |
| /// weaknesses such as seeding from a weak entropy source or leaking state. |
| /// |
| /// [`BlockRngCore`]: block::BlockRngCore |
| </span><span class="kw">pub trait </span>CryptoRng {} |
| |
| <span class="doccomment">/// An extension trait that is automatically implemented for any type |
| /// implementing [`RngCore`] and [`CryptoRng`]. |
| /// |
| /// It may be used as a trait object, and supports upcasting to [`RngCore`] via |
| /// the [`CryptoRngCore::as_rngcore`] method. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use rand_core::CryptoRngCore; |
| /// |
| /// #[allow(unused)] |
| /// fn make_token(rng: &mut dyn CryptoRngCore) -> [u8; 32] { |
| /// let mut buf = [0u8; 32]; |
| /// rng.fill_bytes(&mut buf); |
| /// buf |
| /// } |
| /// ``` |
| </span><span class="kw">pub trait </span>CryptoRngCore: CryptoRng + RngCore { |
| <span class="doccomment">/// Upcast to an [`RngCore`] trait object. |
| </span><span class="kw">fn </span>as_rngcore(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span><span class="kw">dyn </span>RngCore; |
| } |
| |
| <span class="kw">impl</span><T: CryptoRng + RngCore> CryptoRngCore <span class="kw">for </span>T { |
| <span class="kw">fn </span>as_rngcore(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span><span class="kw">dyn </span>RngCore { |
| <span class="self">self |
| </span>} |
| } |
| |
| <span class="doccomment">/// A random number generator that can be explicitly seeded. |
| /// |
| /// This trait encapsulates the low-level functionality common to all |
| /// pseudo-random number generators (PRNGs, or algorithmic generators). |
| /// |
| /// [`rand`]: https://docs.rs/rand |
| </span><span class="kw">pub trait </span>SeedableRng: Sized { |
| <span class="doccomment">/// Seed type, which is restricted to types mutably-dereferenceable as `u8` |
| /// arrays (we recommend `[u8; N]` for some `N`). |
| /// |
| /// It is recommended to seed PRNGs with a seed of at least circa 100 bits, |
| /// which means an array of `[u8; 12]` or greater to avoid picking RNGs with |
| /// partially overlapping periods. |
| /// |
| /// For cryptographic RNG's a seed of 256 bits is recommended, `[u8; 32]`. |
| /// |
| /// |
| /// # Implementing `SeedableRng` for RNGs with large seeds |
| /// |
| /// Note that the required traits `core::default::Default` and |
| /// `core::convert::AsMut<u8>` are not implemented for large arrays |
| /// `[u8; N]` with `N` > 32. To be able to implement the traits required by |
| /// `SeedableRng` for RNGs with such large seeds, the newtype pattern can be |
| /// used: |
| /// |
| /// ``` |
| /// use rand_core::SeedableRng; |
| /// |
| /// const N: usize = 64; |
| /// pub struct MyRngSeed(pub [u8; N]); |
| /// pub struct MyRng(MyRngSeed); |
| /// |
| /// impl Default for MyRngSeed { |
| /// fn default() -> MyRngSeed { |
| /// MyRngSeed([0; N]) |
| /// } |
| /// } |
| /// |
| /// impl AsMut<[u8]> for MyRngSeed { |
| /// fn as_mut(&mut self) -> &mut [u8] { |
| /// &mut self.0 |
| /// } |
| /// } |
| /// |
| /// impl SeedableRng for MyRng { |
| /// type Seed = MyRngSeed; |
| /// |
| /// fn from_seed(seed: MyRngSeed) -> MyRng { |
| /// MyRng(seed) |
| /// } |
| /// } |
| /// ``` |
| </span><span class="kw">type </span>Seed: Sized + Default + AsMut<[u8]>; |
| |
| <span class="doccomment">/// Create a new PRNG using the given seed. |
| /// |
| /// 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 |
| /// `seed_from_u64` instead. |
| /// |
| /// All PRNG implementations should be reproducible unless otherwise noted: |
| /// given a fixed `seed`, 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. |
| /// |
| /// 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. |
| /// |
| /// PRNG implementations should make sure `from_seed` 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 `0xBAD5EEDu32` or `0x0DDB1A5E5BAD5EEDu64` ("odd biases? bad |
| /// seed"). This is assuming only a small number of values must be rejected. |
| </span><span class="kw">fn </span>from_seed(seed: <span class="self">Self</span>::Seed) -> <span class="self">Self</span>; |
| |
| <span class="doccomment">/// Create a new PRNG using a `u64` seed. |
| /// |
| /// This is a convenience-wrapper around `from_seed` to allow construction |
| /// of any `SeedableRng` from a simple `u64` 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. |
| /// |
| /// This **is not suitable for cryptography**, as should be clear given that |
| /// the input size is only 64 bits. |
| /// |
| /// Implementations for PRNGs *may* provide their own implementations of |
| /// this function, but the default implementation should be good enough for |
| /// all purposes. *Changing* the implementation of this function should be |
| /// considered a value-breaking change. |
| </span><span class="kw">fn </span>seed_from_u64(<span class="kw-2">mut </span>state: u64) -> <span class="self">Self </span>{ |
| <span class="comment">// We use PCG32 to generate a u32 sequence, and copy to the seed |
| </span><span class="kw">fn </span>pcg32(state: <span class="kw-2">&mut </span>u64) -> [u8; <span class="number">4</span>] { |
| <span class="kw">const </span>MUL: u64 = <span class="number">6364136223846793005</span>; |
| <span class="kw">const </span>INC: u64 = <span class="number">11634580027462260723</span>; |
| |
| <span class="comment">// We advance the state first (to get away from the input value, |
| // in case it has low Hamming Weight). |
| </span><span class="kw-2">*</span>state = state.wrapping_mul(MUL).wrapping_add(INC); |
| <span class="kw">let </span>state = <span class="kw-2">*</span>state; |
| |
| <span class="comment">// Use PCG output function with to_le to generate x: |
| </span><span class="kw">let </span>xorshifted = (((state >> <span class="number">18</span>) ^ state) >> <span class="number">27</span>) <span class="kw">as </span>u32; |
| <span class="kw">let </span>rot = (state >> <span class="number">59</span>) <span class="kw">as </span>u32; |
| <span class="kw">let </span>x = xorshifted.rotate_right(rot); |
| x.to_le_bytes() |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>seed = <span class="self">Self</span>::Seed::default(); |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = seed.as_mut().chunks_exact_mut(<span class="number">4</span>); |
| <span class="kw">for </span>chunk <span class="kw">in </span><span class="kw-2">&mut </span>iter { |
| chunk.copy_from_slice(<span class="kw-2">&</span>pcg32(<span class="kw-2">&mut </span>state)); |
| } |
| <span class="kw">let </span>rem = iter.into_remainder(); |
| <span class="kw">if </span>!rem.is_empty() { |
| rem.copy_from_slice(<span class="kw-2">&</span>pcg32(<span class="kw-2">&mut </span>state)[..rem.len()]); |
| } |
| |
| <span class="self">Self</span>::from_seed(seed) |
| } |
| |
| <span class="doccomment">/// Create a new PRNG seeded from another `Rng`. |
| /// |
| /// 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. |
| /// |
| /// 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 |
| /// `from_seed`. |
| /// |
| /// Note that seeding `XorShiftRng` from another `XorShiftRng` provides an |
| /// extreme example of what can go wrong: the new PRNG will be a clone |
| /// of the parent. |
| /// |
| /// PRNG implementations are allowed to assume that a good RNG is provided |
| /// for seeding, and that it is cryptographically secure when appropriate. |
| /// As of `rand` 0.7 / `rand_core` 0.5, implementations overriding this |
| /// method should ensure the implementation satisfies reproducibility |
| /// (in prior versions this was not required). |
| /// |
| /// [`rand`]: https://docs.rs/rand |
| </span><span class="kw">fn </span>from_rng<R: RngCore>(<span class="kw-2">mut </span>rng: R) -> <span class="prelude-ty">Result</span><<span class="self">Self</span>, Error> { |
| <span class="kw">let </span><span class="kw-2">mut </span>seed = <span class="self">Self</span>::Seed::default(); |
| rng.try_fill_bytes(seed.as_mut())<span class="question-mark">?</span>; |
| <span class="prelude-val">Ok</span>(<span class="self">Self</span>::from_seed(seed)) |
| } |
| |
| <span class="doccomment">/// Creates a new instance of the RNG seeded via [`getrandom`]. |
| /// |
| /// This method is the recommended way to construct non-deterministic PRNGs |
| /// since it is convenient and secure. |
| /// |
| /// In case the overhead of using [`getrandom`] to seed *many* PRNGs is an |
| /// issue, one may prefer to seed from a local PRNG, e.g. |
| /// `from_rng(thread_rng()).unwrap()`. |
| /// |
| /// # Panics |
| /// |
| /// If [`getrandom`] is unable to provide secure entropy this method will panic. |
| /// |
| /// [`getrandom`]: https://docs.rs/getrandom |
| </span><span class="attribute">#[cfg(feature = <span class="string">"getrandom"</span>)] |
| #[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"getrandom"</span>)))] |
| </span><span class="kw">fn </span>from_entropy() -> <span class="self">Self </span>{ |
| <span class="kw">let </span><span class="kw-2">mut </span>seed = <span class="self">Self</span>::Seed::default(); |
| <span class="kw">if let </span><span class="prelude-val">Err</span>(err) = getrandom::getrandom(seed.as_mut()) { |
| <span class="macro">panic!</span>(<span class="string">"from_entropy failed: {}"</span>, err); |
| } |
| <span class="self">Self</span>::from_seed(seed) |
| } |
| } |
| |
| <span class="comment">// Implement `RngCore` for references to an `RngCore`. |
| // Force inlining all functions, so that it is up to the `RngCore` |
| // implementation and the optimizer to decide on inlining. |
| </span><span class="kw">impl</span><<span class="lifetime">'a</span>, R: RngCore + <span class="question-mark">?</span>Sized> RngCore <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>R { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>next_u32(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| (<span class="kw-2">**</span><span class="self">self</span>).next_u32() |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>next_u64(<span class="kw-2">&mut </span><span class="self">self</span>) -> u64 { |
| (<span class="kw-2">**</span><span class="self">self</span>).next_u64() |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </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]) { |
| (<span class="kw-2">**</span><span class="self">self</span>).fill_bytes(dest) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </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="kw-2">**</span><span class="self">self</span>).try_fill_bytes(dest) |
| } |
| } |
| |
| <span class="comment">// Implement `RngCore` for boxed references to an `RngCore`. |
| // Force inlining all functions, so that it is up to the `RngCore` |
| // implementation and the optimizer to decide on inlining. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">impl</span><R: RngCore + <span class="question-mark">?</span>Sized> RngCore <span class="kw">for </span>Box<R> { |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>next_u32(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| (<span class="kw-2">**</span><span class="self">self</span>).next_u32() |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </span><span class="kw">fn </span>next_u64(<span class="kw-2">&mut </span><span class="self">self</span>) -> u64 { |
| (<span class="kw-2">**</span><span class="self">self</span>).next_u64() |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </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]) { |
| (<span class="kw-2">**</span><span class="self">self</span>).fill_bytes(dest) |
| } |
| |
| <span class="attribute">#[inline(always)] |
| </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="kw-2">**</span><span class="self">self</span>).try_fill_bytes(dest) |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">impl </span>std::io::Read <span class="kw">for dyn </span>RngCore { |
| <span class="kw">fn </span>read(<span class="kw-2">&mut </span><span class="self">self</span>, buf: <span class="kw-2">&mut </span>[u8]) -> <span class="prelude-ty">Result</span><usize, std::io::Error> { |
| <span class="self">self</span>.try_fill_bytes(buf)<span class="question-mark">?</span>; |
| <span class="prelude-val">Ok</span>(buf.len()) |
| } |
| } |
| |
| <span class="comment">// Implement `CryptoRng` for references to a `CryptoRng`. |
| </span><span class="kw">impl</span><<span class="lifetime">'a</span>, R: CryptoRng + <span class="question-mark">?</span>Sized> CryptoRng <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span><span class="kw-2">mut </span>R {} |
| |
| <span class="comment">// Implement `CryptoRng` for boxed references to a `CryptoRng`. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"alloc"</span>)] |
| </span><span class="kw">impl</span><R: CryptoRng + <span class="question-mark">?</span>Sized> CryptoRng <span class="kw">for </span>Box<R> {} |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_seed_from_u64() { |
| <span class="kw">struct </span>SeedableNum(u64); |
| <span class="kw">impl </span>SeedableRng <span class="kw">for </span>SeedableNum { |
| <span class="kw">type </span>Seed = [u8; <span class="number">8</span>]; |
| |
| <span class="kw">fn </span>from_seed(seed: <span class="self">Self</span>::Seed) -> <span class="self">Self </span>{ |
| <span class="kw">let </span><span class="kw-2">mut </span>x = [<span class="number">0u64</span>; <span class="number">1</span>]; |
| le::read_u64_into(<span class="kw-2">&</span>seed, <span class="kw-2">&mut </span>x); |
| SeedableNum(x[<span class="number">0</span>]) |
| } |
| } |
| |
| <span class="kw">const </span>N: usize = <span class="number">8</span>; |
| <span class="kw">const </span>SEEDS: [u64; N] = [<span class="number">0u64</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">8</span>, <span class="number">16</span>, -<span class="number">1i64 </span><span class="kw">as </span>u64]; |
| <span class="kw">let </span><span class="kw-2">mut </span>results = [<span class="number">0u64</span>; N]; |
| <span class="kw">for </span>(i, seed) <span class="kw">in </span>SEEDS.iter().enumerate() { |
| <span class="kw">let </span>SeedableNum(x) = SeedableNum::seed_from_u64(<span class="kw-2">*</span>seed); |
| results[i] = x; |
| } |
| |
| <span class="kw">for </span>(i1, r1) <span class="kw">in </span>results.iter().enumerate() { |
| <span class="kw">let </span>weight = r1.count_ones(); |
| <span class="comment">// This is the binomial distribution B(64, 0.5), so chance of |
| // weight < 20 is binocdf(19, 64, 0.5) = 7.8e-4, and same for |
| // weight > 44. |
| </span><span class="macro">assert!</span>((<span class="number">20</span>..=<span class="number">44</span>).contains(<span class="kw-2">&</span>weight)); |
| |
| <span class="kw">for </span>(i2, r2) <span class="kw">in </span>results.iter().enumerate() { |
| <span class="kw">if </span>i1 == i2 { |
| <span class="kw">continue</span>; |
| } |
| <span class="kw">let </span>diff_weight = (r1 ^ r2).count_ones(); |
| <span class="macro">assert!</span>(diff_weight >= <span class="number">20</span>); |
| } |
| } |
| |
| <span class="comment">// value-breakage test: |
| </span><span class="macro">assert_eq!</span>(results[<span class="number">0</span>], <span class="number">5029875928683246316</span>); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="rand_core" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
