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</pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 &lt;LICENSE-APACHE or</span>
<span class="comment">// https://www.apache.org/licenses/LICENSE-2.0&gt; or the MIT license</span>
<span class="comment">// &lt;LICENSE-MIT or https://opensource.org/licenses/MIT&gt;, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! The standard RNG</span>
<span class="kw">use</span> <span class="kw">crate</span>::{<span class="ident">CryptoRng</span>, <span class="ident">Error</span>, <span class="ident">RngCore</span>, <span class="ident">SeedableRng</span>};
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">use</span> <span class="ident">rand_chacha::ChaCha12Core</span> <span class="kw">as</span> <span class="ident">Core</span>;
<span class="kw">use</span> <span class="ident">rand_chacha::ChaCha12Rng</span> <span class="kw">as</span> <span class="ident">Rng</span>;
<span class="doccomment">/// The standard RNG. The PRNG algorithm in `StdRng` is chosen to be efficient</span>
<span class="doccomment">/// on the current platform, to be statistically strong and unpredictable</span>
<span class="doccomment">/// (meaning a cryptographically secure PRNG).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The current algorithm used is the ChaCha block cipher with 12 rounds. Please</span>
<span class="doccomment">/// see this relevant [rand issue] for the discussion. This may change as new </span>
<span class="doccomment">/// evidence of cipher security and performance becomes available.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The algorithm is deterministic but should not be considered reproducible</span>
<span class="doccomment">/// due to dependence on configuration and possible replacement in future</span>
<span class="doccomment">/// library versions. For a secure reproducible generator, we recommend use of</span>
<span class="doccomment">/// the [rand_chacha] crate directly.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [rand_chacha]: https://crates.io/crates/rand_chacha</span>
<span class="doccomment">/// [rand issue]: https://github.com/rust-random/rand/issues/932</span>
<span class="attribute">#[<span class="ident">cfg_attr</span>(<span class="ident">doc_cfg</span>, <span class="ident">doc</span>(<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std_rng&quot;</span>)))]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">StdRng</span>(<span class="ident">Rng</span>);
<span class="kw">impl</span> <span class="ident">RngCore</span> <span class="kw">for</span> <span class="ident">StdRng</span> {
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>) -&gt; <span class="ident">u32</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_u32</span>()
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>) -&gt; <span class="ident">u64</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">next_u64</span>()
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&amp;mut</span> [<span class="ident">u8</span>]) {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">fill_bytes</span>(<span class="ident">dest</span>);
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">try_fill_bytes</span>(<span class="kw-2">&amp;mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&amp;mut</span> [<span class="ident">u8</span>]) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span>(), <span class="ident">Error</span><span class="op">&gt;</span> {
<span class="self">self</span>.<span class="number">0</span>.<span class="ident">try_fill_bytes</span>(<span class="ident">dest</span>)
}
}
<span class="kw">impl</span> <span class="ident">SeedableRng</span> <span class="kw">for</span> <span class="ident">StdRng</span> {
<span class="kw">type</span> <span class="ident">Seed</span> <span class="op">=</span> <span class="op">&lt;</span><span class="ident">Rng</span> <span class="kw">as</span> <span class="ident">SeedableRng</span><span class="op">&gt;</span><span class="ident">::Seed</span>;
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">from_seed</span>(<span class="ident">seed</span>: <span class="ident"><span class="self">Self</span>::Seed</span>) -&gt; <span class="self">Self</span> {
<span class="ident">StdRng</span>(<span class="ident">Rng::from_seed</span>(<span class="ident">seed</span>))
}
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">fn</span> <span class="ident">from_rng</span><span class="op">&lt;</span><span class="ident">R</span>: <span class="ident">RngCore</span><span class="op">&gt;</span>(<span class="ident">rng</span>: <span class="ident">R</span>) -&gt; <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="self">Self</span>, <span class="ident">Error</span><span class="op">&gt;</span> {
<span class="ident">Rng::from_rng</span>(<span class="ident">rng</span>).<span class="ident">map</span>(<span class="ident">StdRng</span>)
}
}
<span class="kw">impl</span> <span class="ident">CryptoRng</span> <span class="kw">for</span> <span class="ident">StdRng</span> {}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">test</span> {
<span class="kw">use</span> <span class="ident"><span class="kw">crate</span>::rngs::StdRng</span>;
<span class="kw">use</span> <span class="kw">crate</span>::{<span class="ident">RngCore</span>, <span class="ident">SeedableRng</span>};
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_stdrng_construction</span>() {
<span class="comment">// Test value-stability of StdRng. This is expected to break any time</span>
<span class="comment">// the algorithm is changed.</span>
<span class="attribute">#[<span class="ident">rustfmt::skip</span>]</span>
<span class="kw">let</span> <span class="ident">seed</span> <span class="op">=</span> [<span class="number">1</span>,<span class="number">0</span>,<span class="number">0</span>,<span class="number">0</span>, <span class="number">23</span>,<span class="number">0</span>,<span class="number">0</span>,<span class="number">0</span>, <span class="number">200</span>,<span class="number">1</span>,<span class="number">0</span>,<span class="number">0</span>, <span class="number">210</span>,<span class="number">30</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">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">0</span>,<span class="number">0</span>,<span class="number">0</span>,<span class="number">0</span>];
<span class="kw">let</span> <span class="ident">target</span> <span class="op">=</span> [<span class="number">10719222850664546238</span>, <span class="number">14064965282130556830</span>];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng0</span> <span class="op">=</span> <span class="ident">StdRng::from_seed</span>(<span class="ident">seed</span>);
<span class="kw">let</span> <span class="ident">x0</span> <span class="op">=</span> <span class="ident">rng0</span>.<span class="ident">next_u64</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng1</span> <span class="op">=</span> <span class="ident">StdRng::from_rng</span>(<span class="ident">rng0</span>).<span class="ident">unwrap</span>();
<span class="kw">let</span> <span class="ident">x1</span> <span class="op">=</span> <span class="ident">rng1</span>.<span class="ident">next_u64</span>();
<span class="macro">assert_eq!</span>([<span class="ident">x0</span>, <span class="ident">x1</span>], <span class="ident">target</span>);
}
}
</code></pre></div>
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