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</pre><pre class="rust"><code><span class="comment">// Copyright 2019 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">//! Interface to the random number generator of the operating system.</span>
<span class="kw">use</span> <span class="kw">crate</span>::{<span class="ident">impls</span>, <span class="ident">CryptoRng</span>, <span class="ident">Error</span>, <span class="ident">RngCore</span>};
<span class="kw">use</span> <span class="ident">getrandom::getrandom</span>;
<span class="doccomment">/// A random number generator that retrieves randomness from the</span>
<span class="doccomment">/// operating system.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is a zero-sized struct. It can be freely constructed with `OsRng`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The implementation is provided by the [getrandom] crate. Refer to</span>
<span class="doccomment">/// [getrandom] documentation for details.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This struct is only available when specifying the crate feature `getrandom`</span>
<span class="doccomment">/// or `std`. When using the `rand` lib, it is also available as `rand::rngs::OsRng`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Blocking and error handling</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It is possible that when used during early boot the first call to `OsRng`</span>
<span class="doccomment">/// will block until the system&#39;s RNG is initialised. It is also possible</span>
<span class="doccomment">/// (though highly unlikely) for `OsRng` to fail on some platforms, most</span>
<span class="doccomment">/// likely due to system mis-configuration.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// After the first successful call, it is highly unlikely that failures or</span>
<span class="doccomment">/// significant delays will occur (although performance should be expected to</span>
<span class="doccomment">/// be much slower than a user-space PRNG).</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Usage example</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use rand_core::{RngCore, OsRng};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let mut key = [0u8; 16];</span>
<span class="doccomment">/// OsRng.fill_bytes(&amp;mut key);</span>
<span class="doccomment">/// let random_u64 = OsRng.next_u64();</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [getrandom]: https://crates.io/crates/getrandom</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;getrandom&quot;</span>)))]</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Debug</span>, <span class="ident">Default</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">OsRng</span>;
<span class="kw">impl</span> <span class="ident">CryptoRng</span> <span class="kw">for</span> <span class="ident">OsRng</span> {}
<span class="kw">impl</span> <span class="ident">RngCore</span> <span class="kw">for</span> <span class="ident">OsRng</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="ident">impls::next_u32_via_fill</span>(<span class="self">self</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="ident">impls::next_u64_via_fill</span>(<span class="self">self</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="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Err</span>(<span class="ident">e</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">try_fill_bytes</span>(<span class="ident">dest</span>) {
<span class="macro">panic!</span>(<span class="string">&quot;Error: {}&quot;</span>, <span class="ident">e</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="ident">getrandom</span>(<span class="ident">dest</span>)<span class="question-mark">?</span>;
<span class="prelude-val">Ok</span>(())
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_os_rng</span>() {
<span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">OsRng</span>.<span class="ident">next_u64</span>();
<span class="kw">let</span> <span class="ident">y</span> <span class="op">=</span> <span class="ident">OsRng</span>.<span class="ident">next_u64</span>();
<span class="macro">assert!</span>(<span class="ident">x</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span>);
<span class="macro">assert!</span>(<span class="ident">x</span> <span class="op">!</span><span class="op">=</span> <span class="ident">y</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_construction</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> <span class="ident">OsRng::default</span>();
<span class="macro">assert!</span>(<span class="ident">rng</span>.<span class="ident">next_u64</span>() <span class="op">!</span><span class="op">=</span> <span class="number">0</span>);
}
</code></pre></div>
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