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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">//! Random number generators and adapters</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! ## Background: Random number generators (RNGs)</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! Computers cannot produce random numbers from nowhere. We classify</span>
 <span class="doccomment">//! random number generators as follows:</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! -   &quot;True&quot; random number generators (TRNGs) use hard-to-predict data sources</span>
 <span class="doccomment">//!     (e.g. the high-resolution parts of event timings and sensor jitter) to</span>
 <span class="doccomment">//!     harvest random bit-sequences, apply algorithms to remove bias and</span>
 <span class="doccomment">//!     estimate available entropy, then combine these bits into a byte-sequence</span>
 <span class="doccomment">//!     or an entropy pool. This job is usually done by the operating system or</span>
 <span class="doccomment">//!     a hardware generator (HRNG).</span>
 <span class="doccomment">//! -   &quot;Pseudo&quot;-random number generators (PRNGs) use algorithms to transform a</span>
 <span class="doccomment">//!     seed into a sequence of pseudo-random numbers. These generators can be</span>
 <span class="doccomment">//!     fast and produce well-distributed unpredictable random numbers (or not).</span>
 <span class="doccomment">//!     They are usually deterministic: given algorithm and seed, the output</span>
 <span class="doccomment">//!     sequence can be reproduced. They have finite period and eventually loop;</span>
 <span class="doccomment">//!     with many algorithms this period is fixed and can be proven sufficiently</span>
 <span class="doccomment">//!     long, while others are chaotic and the period depends on the seed.</span>
 <span class="doccomment">//! -   &quot;Cryptographically secure&quot; pseudo-random number generators (CSPRNGs)</span>
 <span class="doccomment">//!     are the sub-set of PRNGs which are secure. Security of the generator</span>
 <span class="doccomment">//!     relies both on hiding the internal state and using a strong algorithm.</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! ## Traits and functionality</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! All RNGs implement the [`RngCore`] trait, as a consequence of which the</span>
 <span class="doccomment">//! [`Rng`] extension trait is automatically implemented. Secure RNGs may</span>
 <span class="doccomment">//! additionally implement the [`CryptoRng`] trait.</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! All PRNGs require a seed to produce their random number sequence. The</span>
 <span class="doccomment">//! [`SeedableRng`] trait provides three ways of constructing PRNGs:</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! -   `from_seed` accepts a type specific to the PRNG</span>
 <span class="doccomment">//! -   `from_rng` allows a PRNG to be seeded from any other RNG</span>
 <span class="doccomment">//! -   `seed_from_u64` allows any PRNG to be seeded from a `u64` insecurely</span>
 <span class="doccomment">//! -   `from_entropy` securely seeds a PRNG from fresh entropy</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! Use the [`rand_core`] crate when implementing your own RNGs.</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! ## Our generators</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! This crate provides several random number generators:</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! -   [`OsRng`] is an interface to the operating system&#39;s random number</span>
 <span class="doccomment">//!     source. Typically the operating system uses a CSPRNG with entropy</span>
 <span class="doccomment">//!     provided by a TRNG and some type of on-going re-seeding.</span>
 <span class="doccomment">//! -   [`ThreadRng`], provided by the [`thread_rng`] function, is a handle to a</span>
 <span class="doccomment">//!     thread-local CSPRNG with periodic seeding from [`OsRng`]. Because this</span>
 <span class="doccomment">//!     is local, it is typically much faster than [`OsRng`]. It should be</span>
 <span class="doccomment">//!     secure, though the paranoid may prefer [`OsRng`].</span>
 <span class="doccomment">//! -   [`StdRng`] is a CSPRNG chosen for good performance and trust of security</span>
 <span class="doccomment">//!     (based on reviews, maturity and usage). The current algorithm is ChaCha12,</span>
 <span class="doccomment">//!     which is well established and rigorously analysed.</span>
 <span class="doccomment">//!     [`StdRng`] provides the algorithm used by [`ThreadRng`] but without</span>
 <span class="doccomment">//!     periodic reseeding.</span>
 <span class="doccomment">//! -   [`SmallRng`] is an **insecure** PRNG designed to be fast, simple, require</span>
 <span class="doccomment">//!     little memory, and have good output quality.</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! The algorithms selected for [`StdRng`] and [`SmallRng`] may change in any</span>
 <span class="doccomment">//! release and may be platform-dependent, therefore they should be considered</span>
 <span class="doccomment">//! **not reproducible**.</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! ## Additional generators</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! **TRNGs**: The [`rdrand`] crate provides an interface to the RDRAND and</span>
 <span class="doccomment">//! RDSEED instructions available in modern Intel and AMD CPUs.</span>
 <span class="doccomment">//! The [`rand_jitter`] crate provides a user-space implementation of</span>
 <span class="doccomment">//! entropy harvesting from CPU timer jitter, but is very slow and has</span>
 <span class="doccomment">//! [security issues](https://github.com/rust-random/rand/issues/699).</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! **PRNGs**: Several companion crates are available, providing individual or</span>
 <span class="doccomment">//! families of PRNG algorithms. These provide the implementations behind</span>
 <span class="doccomment">//! [`StdRng`] and [`SmallRng`] but can also be used directly, indeed *should*</span>
 <span class="doccomment">//! be used directly when **reproducibility** matters.</span>
 <span class="doccomment">//! Some suggestions are: [`rand_chacha`], [`rand_pcg`], [`rand_xoshiro`].</span>
 <span class="doccomment">//! A full list can be found by searching for crates with the [`rng` tag].</span>
 <span class="doccomment">//!</span>
 <span class="doccomment">//! [`Rng`]: crate::Rng</span>
 <span class="doccomment">//! [`RngCore`]: crate::RngCore</span>
 <span class="doccomment">//! [`CryptoRng`]: crate::CryptoRng</span>
 <span class="doccomment">//! [`SeedableRng`]: crate::SeedableRng</span>
 <span class="doccomment">//! [`thread_rng`]: crate::thread_rng</span>
 <span class="doccomment">//! [`rdrand`]: https://crates.io/crates/rdrand</span>
 <span class="doccomment">//! [`rand_jitter`]: https://crates.io/crates/rand_jitter</span>
 <span class="doccomment">//! [`rand_chacha`]: https://crates.io/crates/rand_chacha</span>
 <span class="doccomment">//! [`rand_pcg`]: https://crates.io/crates/rand_pcg</span>
 <span class="doccomment">//! [`rand_xoshiro`]: https://crates.io/crates/rand_xoshiro</span>
 <span class="doccomment">//! [`rng` tag]: https://crates.io/keywords/rng</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&quot;</span>)))]</span>
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std&quot;</span>)]</span> <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">adapter</span>;

 <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">mock</span>; <span class="comment">// Public so we don&#39;t export `StepRng` directly, making it a bit</span>
               <span class="comment">// more clear it is intended for testing.</span>

 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;small_rng&quot;</span>, <span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">&quot;64&quot;</span>))]</span>
 <span class="kw">mod</span> <span class="ident">xoshiro256plusplus</span>;
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;small_rng&quot;</span>, <span class="ident">not</span>(<span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">&quot;64&quot;</span>)))]</span>
 <span class="kw">mod</span> <span class="ident">xoshiro128plusplus</span>;
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;small_rng&quot;</span>)]</span> <span class="kw">mod</span> <span class="ident">small</span>;

 <span class="attribute">#[<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="kw">mod</span> <span class="ident">std</span>;
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std&quot;</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std_rng&quot;</span>))]</span> <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod</span> <span class="ident">thread</span>;

 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;small_rng&quot;</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::small::SmallRng</span>;
 <span class="attribute">#[<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="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::std::StdRng</span>;
 <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std&quot;</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;std_rng&quot;</span>))]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::thread::ThreadRng</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">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">&quot;getrandom&quot;</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">rand_core::OsRng</span>;
 </code></pre></div>
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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 <LICENSE-APACHE or</span>
	<span class="comment">// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
	<span class="comment">// <LICENSE-MIT or https://opensource.org/licenses/MIT>, 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">//! Random number generators and adapters</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! ## Background: Random number generators (RNGs)</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! Computers cannot produce random numbers from nowhere. We classify</span>
	<span class="doccomment">//! random number generators as follows:</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! - "True" random number generators (TRNGs) use hard-to-predict data sources</span>
	<span class="doccomment">//! (e.g. the high-resolution parts of event timings and sensor jitter) to</span>
	<span class="doccomment">//! harvest random bit-sequences, apply algorithms to remove bias and</span>
	<span class="doccomment">//! estimate available entropy, then combine these bits into a byte-sequence</span>
	<span class="doccomment">//! or an entropy pool. This job is usually done by the operating system or</span>
	<span class="doccomment">//! a hardware generator (HRNG).</span>
	<span class="doccomment">//! - "Pseudo"-random number generators (PRNGs) use algorithms to transform a</span>
	<span class="doccomment">//! seed into a sequence of pseudo-random numbers. These generators can be</span>
	<span class="doccomment">//! fast and produce well-distributed unpredictable random numbers (or not).</span>
	<span class="doccomment">//! They are usually deterministic: given algorithm and seed, the output</span>
	<span class="doccomment">//! sequence can be reproduced. They have finite period and eventually loop;</span>
	<span class="doccomment">//! with many algorithms this period is fixed and can be proven sufficiently</span>
	<span class="doccomment">//! long, while others are chaotic and the period depends on the seed.</span>
	<span class="doccomment">//! - "Cryptographically secure" pseudo-random number generators (CSPRNGs)</span>
	<span class="doccomment">//! are the sub-set of PRNGs which are secure. Security of the generator</span>
	<span class="doccomment">//! relies both on hiding the internal state and using a strong algorithm.</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! ## Traits and functionality</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! All RNGs implement the [`RngCore`] trait, as a consequence of which the</span>
	<span class="doccomment">//! [`Rng`] extension trait is automatically implemented. Secure RNGs may</span>
	<span class="doccomment">//! additionally implement the [`CryptoRng`] trait.</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! All PRNGs require a seed to produce their random number sequence. The</span>
	<span class="doccomment">//! [`SeedableRng`] trait provides three ways of constructing PRNGs:</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! - `from_seed` accepts a type specific to the PRNG</span>
	<span class="doccomment">//! - `from_rng` allows a PRNG to be seeded from any other RNG</span>
	<span class="doccomment">//! - `seed_from_u64` allows any PRNG to be seeded from a `u64` insecurely</span>
	<span class="doccomment">//! - `from_entropy` securely seeds a PRNG from fresh entropy</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! Use the [`rand_core`] crate when implementing your own RNGs.</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! ## Our generators</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! This crate provides several random number generators:</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! - [`OsRng`] is an interface to the operating system's random number</span>
	<span class="doccomment">//! source. Typically the operating system uses a CSPRNG with entropy</span>
	<span class="doccomment">//! provided by a TRNG and some type of on-going re-seeding.</span>
	<span class="doccomment">//! - [`ThreadRng`], provided by the [`thread_rng`] function, is a handle to a</span>
	<span class="doccomment">//! thread-local CSPRNG with periodic seeding from [`OsRng`]. Because this</span>
	<span class="doccomment">//! is local, it is typically much faster than [`OsRng`]. It should be</span>
	<span class="doccomment">//! secure, though the paranoid may prefer [`OsRng`].</span>
	<span class="doccomment">//! - [`StdRng`] is a CSPRNG chosen for good performance and trust of security</span>
	<span class="doccomment">//! (based on reviews, maturity and usage). The current algorithm is ChaCha12,</span>
	<span class="doccomment">//! which is well established and rigorously analysed.</span>
	<span class="doccomment">//! [`StdRng`] provides the algorithm used by [`ThreadRng`] but without</span>
	<span class="doccomment">//! periodic reseeding.</span>
	<span class="doccomment">//! - [`SmallRng`] is an insecure PRNG designed to be fast, simple, require</span>
	<span class="doccomment">//! little memory, and have good output quality.</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! The algorithms selected for [`StdRng`] and [`SmallRng`] may change in any</span>
	<span class="doccomment">//! release and may be platform-dependent, therefore they should be considered</span>
	<span class="doccomment">//! not reproducible.</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! ## Additional generators</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! TRNGs: The [`rdrand`] crate provides an interface to the RDRAND and</span>
	<span class="doccomment">//! RDSEED instructions available in modern Intel and AMD CPUs.</span>
	<span class="doccomment">//! The [`rand_jitter`] crate provides a user-space implementation of</span>
	<span class="doccomment">//! entropy harvesting from CPU timer jitter, but is very slow and has</span>
	<span class="doccomment">//! [security issues](https://github.com/rust-random/rand/issues/699).</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! PRNGs: Several companion crates are available, providing individual or</span>
	<span class="doccomment">//! families of PRNG algorithms. These provide the implementations behind</span>
	<span class="doccomment">//! [`StdRng`] and [`SmallRng`] but can also be used directly, indeed should</span>
	<span class="doccomment">//! be used directly when reproducibility matters.</span>
	<span class="doccomment">//! Some suggestions are: [`rand_chacha`], [`rand_pcg`], [`rand_xoshiro`].</span>
	<span class="doccomment">//! A full list can be found by searching for crates with the [`rng` tag].</span>
	<span class="doccomment">//!</span>
	<span class="doccomment">//! [`Rng`]: crate::Rng</span>
	<span class="doccomment">//! [`RngCore`]: crate::RngCore</span>
	<span class="doccomment">//! [`CryptoRng`]: crate::CryptoRng</span>
	<span class="doccomment">//! [`SeedableRng`]: crate::SeedableRng</span>
	<span class="doccomment">//! [`thread_rng`]: crate::thread_rng</span>
	<span class="doccomment">//! [`rdrand`]: https://crates.io/crates/rdrand</span>
	<span class="doccomment">//! [`rand_jitter`]: https://crates.io/crates/rand_jitter</span>
	<span class="doccomment">//! [`rand_chacha`]: https://crates.io/crates/rand_chacha</span>
	<span class="doccomment">//! [`rand_pcg`]: https://crates.io/crates/rand_pcg</span>
	<span class="doccomment">//! [`rand_xoshiro`]: https://crates.io/crates/rand_xoshiro</span>
	<span class="doccomment">//! [`rng` tag]: https://crates.io/keywords/rng</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">"std"</span>)))]</span>
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std"</span>)]</span> <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">adapter</span>;

	<span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">mock</span>; <span class="comment">// Public so we don't export `StepRng` directly, making it a bit</span>
	<span class="comment">// more clear it is intended for testing.</span>

	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"small_rng"</span>, <span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">"64"</span>))]</span>
	<span class="kw">mod</span> <span class="ident">xoshiro256plusplus</span>;
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"small_rng"</span>, <span class="ident">not</span>(<span class="ident">target_pointer_width</span> <span class="op">=</span> <span class="string">"64"</span>)))]</span>
	<span class="kw">mod</span> <span class="ident">xoshiro128plusplus</span>;
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"small_rng"</span>)]</span> <span class="kw">mod</span> <span class="ident">small</span>;

	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std_rng"</span>)]</span> <span class="kw">mod</span> <span class="ident">std</span>;
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"std_rng"</span>))]</span> <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod</span> <span class="ident">thread</span>;

	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"small_rng"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::small::SmallRng</span>;
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std_rng"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::std::StdRng</span>;
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">all</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"std"</span>, <span class="ident">feature</span> <span class="op">=</span> <span class="string">"std_rng"</span>))]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident"><span class="self">self</span>::thread::ThreadRng</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">"getrandom"</span>)))]</span>
	<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"getrandom"</span>)]</span> <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">rand_core::OsRng</span>;
	</code></pre></div>
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