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</pre><pre class="rust ">
<span class="comment">// Copyright 2013 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://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">//! A wrapper around another RNG that reseeds it after it</span>
<span class="doccomment">//! generates a certain number of random bytes.</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">default</span>::<span class="ident">Default</span>;
<span class="kw">use</span> {<span class="ident">Rng</span>, <span class="ident">SeedableRng</span>};
<span class="doccomment">/// How many bytes of entropy the underling RNG is allowed to generate</span>
<span class="doccomment">/// before it is reseeded</span>
<span class="kw">const</span> <span class="ident">DEFAULT_GENERATION_THRESHOLD</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">32</span> <span class="op">*</span> <span class="number">1024</span>;
<span class="doccomment">/// A wrapper around any RNG which reseeds the underlying RNG after it</span>
<span class="doccomment">/// has generated a certain number of random bytes.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">Rsdr</span><span class="op">></span> {
<span class="ident">rng</span>: <span class="ident">R</span>,
<span class="ident">generation_threshold</span>: <span class="ident">u64</span>,
<span class="ident">bytes_generated</span>: <span class="ident">u64</span>,
<span class="doccomment">/// Controls the behaviour when reseeding the RNG.</span>
<span class="kw">pub</span> <span class="ident">reseeder</span>: <span class="ident">Rsdr</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Rng</span>, <span class="ident">Rsdr</span>: <span class="ident">Reseeder</span><span class="op"><</span><span class="ident">R</span><span class="op">>></span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">Rsdr</span><span class="op">></span> {
<span class="doccomment">/// Create a new `ReseedingRng` with the given parameters.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Arguments</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * `rng`: the random number generator to use.</span>
<span class="doccomment">/// * `generation_threshold`: the number of bytes of entropy at which to reseed the RNG.</span>
<span class="doccomment">/// * `reseeder`: the reseeding object to use.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">rng</span>: <span class="ident">R</span>, <span class="ident">generation_threshold</span>: <span class="ident">u64</span>, <span class="ident">reseeder</span>: <span class="ident">Rsdr</span>) <span class="op">-></span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>,<span class="ident">Rsdr</span><span class="op">></span> {
<span class="ident">ReseedingRng</span> {
<span class="ident">rng</span>: <span class="ident">rng</span>,
<span class="ident">generation_threshold</span>: <span class="ident">generation_threshold</span>,
<span class="ident">bytes_generated</span>: <span class="number">0</span>,
<span class="ident">reseeder</span>: <span class="ident">reseeder</span>
}
}
<span class="doccomment">/// Reseed the internal RNG if the number of bytes that have been</span>
<span class="doccomment">/// generated exceed the threshold.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">reseed_if_necessary</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">>=</span> <span class="self">self</span>.<span class="ident">generation_threshold</span> {
<span class="self">self</span>.<span class="ident">reseeder</span>.<span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">rng</span>);
<span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">=</span> <span class="number">0</span>;
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Rng</span>, <span class="ident">Rsdr</span>: <span class="ident">Reseeder</span><span class="op"><</span><span class="ident">R</span><span class="op">>></span> <span class="ident">Rng</span> <span class="kw">for</span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">Rsdr</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u32</span> {
<span class="self">self</span>.<span class="ident">reseed_if_necessary</span>();
<span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">+=</span> <span class="number">4</span>;
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">next_u32</span>()
}
<span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="self">self</span>.<span class="ident">reseed_if_necessary</span>();
<span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">+=</span> <span class="number">8</span>;
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">next_u64</span>()
}
<span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> [<span class="ident">u8</span>]) {
<span class="self">self</span>.<span class="ident">reseed_if_necessary</span>();
<span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">+=</span> <span class="ident">dest</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">u64</span>;
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">fill_bytes</span>(<span class="ident">dest</span>)
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">S</span>, <span class="ident">R</span>: <span class="ident">SeedableRng</span><span class="op"><</span><span class="ident">S</span><span class="op">></span>, <span class="ident">Rsdr</span>: <span class="ident">Reseeder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> <span class="op">+</span> <span class="ident">Default</span><span class="op">></span>
<span class="ident">SeedableRng</span><span class="op"><</span>(<span class="ident">Rsdr</span>, <span class="ident">S</span>)<span class="op">></span> <span class="kw">for</span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">Rsdr</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, (<span class="ident">rsdr</span>, <span class="ident">seed</span>): (<span class="ident">Rsdr</span>, <span class="ident">S</span>)) {
<span class="self">self</span>.<span class="ident">rng</span>.<span class="ident">reseed</span>(<span class="ident">seed</span>);
<span class="self">self</span>.<span class="ident">reseeder</span> <span class="op">=</span> <span class="ident">rsdr</span>;
<span class="self">self</span>.<span class="ident">bytes_generated</span> <span class="op">=</span> <span class="number">0</span>;
}
<span class="doccomment">/// Create a new `ReseedingRng` from the given reseeder and</span>
<span class="doccomment">/// seed. This uses a default value for `generation_threshold`.</span>
<span class="kw">fn</span> <span class="ident">from_seed</span>((<span class="ident">rsdr</span>, <span class="ident">seed</span>): (<span class="ident">Rsdr</span>, <span class="ident">S</span>)) <span class="op">-></span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">R</span>, <span class="ident">Rsdr</span><span class="op">></span> {
<span class="ident">ReseedingRng</span> {
<span class="ident">rng</span>: <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>(<span class="ident">seed</span>),
<span class="ident">generation_threshold</span>: <span class="ident">DEFAULT_GENERATION_THRESHOLD</span>,
<span class="ident">bytes_generated</span>: <span class="number">0</span>,
<span class="ident">reseeder</span>: <span class="ident">rsdr</span>
}
}
}
<span class="doccomment">/// Something that can be used to reseed an RNG via `ReseedingRng`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Example</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust</span>
<span class="doccomment">/// use rand::{Rng, SeedableRng, StdRng};</span>
<span class="doccomment">/// use rand::reseeding::{Reseeder, ReseedingRng};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// struct TickTockReseeder { tick: bool }</span>
<span class="doccomment">/// impl Reseeder<StdRng> for TickTockReseeder {</span>
<span class="doccomment">/// fn reseed(&mut self, rng: &mut StdRng) {</span>
<span class="doccomment">/// let val = if self.tick {0} else {1};</span>
<span class="doccomment">/// rng.reseed(&[val]);</span>
<span class="doccomment">/// self.tick = !self.tick;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// fn main() {</span>
<span class="doccomment">/// let rsdr = TickTockReseeder { tick: true };</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let inner = StdRng::new().unwrap();</span>
<span class="doccomment">/// let mut rng = ReseedingRng::new(inner, 10, rsdr);</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // this will repeat, because it gets reseeded very regularly.</span>
<span class="doccomment">/// let s: String = rng.gen_ascii_chars().take(100).collect();</span>
<span class="doccomment">/// println!("{}", s);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Reseeder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> {
<span class="doccomment">/// Reseed the given RNG.</span>
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">rng</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>);
}
<span class="doccomment">/// Reseed an RNG using a `Default` instance. This reseeds by</span>
<span class="doccomment">/// replacing the RNG with the result of a `Default::default` call.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ReseedWithDefault</span>;
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Rng</span> <span class="op">+</span> <span class="ident">Default</span><span class="op">></span> <span class="ident">Reseeder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> <span class="kw">for</span> <span class="ident">ReseedWithDefault</span> {
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">rng</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) {
<span class="kw-2">*</span><span class="ident">rng</span> <span class="op">=</span> <span class="ident">Default</span>::<span class="ident">default</span>();
}
}
<span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">ReseedWithDefault</span> {
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="ident">ReseedWithDefault</span> { <span class="ident">ReseedWithDefault</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">std</span>::<span class="ident">default</span>::<span class="ident">Default</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">iter</span>::<span class="ident">repeat</span>;
<span class="kw">use</span> <span class="kw">super</span>::{<span class="ident">ReseedingRng</span>, <span class="ident">ReseedWithDefault</span>};
<span class="kw">use</span> {<span class="ident">SeedableRng</span>, <span class="ident">Rng</span>};
<span class="kw">struct</span> <span class="ident">Counter</span> {
<span class="ident">i</span>: <span class="ident">u32</span>
}
<span class="kw">impl</span> <span class="ident">Rng</span> <span class="kw">for</span> <span class="ident">Counter</span> {
<span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">u32</span> {
<span class="self">self</span>.<span class="ident">i</span> <span class="op">+=</span> <span class="number">1</span>;
<span class="comment">// very random</span>
<span class="self">self</span>.<span class="ident">i</span> <span class="op">-</span> <span class="number">1</span>
}
}
<span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">Counter</span> {
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="ident">Counter</span> {
<span class="ident">Counter</span> { <span class="ident">i</span>: <span class="number">0</span> }
}
}
<span class="kw">impl</span> <span class="ident">SeedableRng</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="kw">for</span> <span class="ident">Counter</span> {
<span class="kw">fn</span> <span class="ident">reseed</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">seed</span>: <span class="ident">u32</span>) {
<span class="self">self</span>.<span class="ident">i</span> <span class="op">=</span> <span class="ident">seed</span>;
}
<span class="kw">fn</span> <span class="ident">from_seed</span>(<span class="ident">seed</span>: <span class="ident">u32</span>) <span class="op">-></span> <span class="ident">Counter</span> {
<span class="ident">Counter</span> { <span class="ident">i</span>: <span class="ident">seed</span> }
}
}
<span class="kw">type</span> <span class="ident">MyRng</span> <span class="op">=</span> <span class="ident">ReseedingRng</span><span class="op"><</span><span class="ident">Counter</span>, <span class="ident">ReseedWithDefault</span><span class="op">></span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_reseeding</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rs</span> <span class="op">=</span> <span class="ident">ReseedingRng</span>::<span class="ident">new</span>(<span class="ident">Counter</span> {<span class="ident">i</span>:<span class="number">0</span>}, <span class="number">400</span>, <span class="ident">ReseedWithDefault</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">i</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> _ <span class="kw">in</span> <span class="number">0</span>..<span class="number">1000</span> {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">rs</span>.<span class="ident">next_u32</span>(), <span class="ident">i</span> <span class="op">%</span> <span class="number">100</span>);
<span class="ident">i</span> <span class="op">+=</span> <span class="number">1</span>;
}
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_rng_seeded</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">ra</span>: <span class="ident">MyRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>((<span class="ident">ReseedWithDefault</span>, <span class="number">2</span>));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rb</span>: <span class="ident">MyRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>((<span class="ident">ReseedWithDefault</span>, <span class="number">2</span>));
<span class="macro">assert</span><span class="macro">!</span>(::<span class="ident">test</span>::<span class="ident">iter_eq</span>(<span class="ident">ra</span>.<span class="ident">gen_ascii_chars</span>().<span class="ident">take</span>(<span class="number">100</span>),
<span class="ident">rb</span>.<span class="ident">gen_ascii_chars</span>().<span class="ident">take</span>(<span class="number">100</span>)));
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_rng_reseed</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">r</span>: <span class="ident">MyRng</span> <span class="op">=</span> <span class="ident">SeedableRng</span>::<span class="ident">from_seed</span>((<span class="ident">ReseedWithDefault</span>, <span class="number">3</span>));
<span class="kw">let</span> <span class="ident">string1</span>: <span class="ident">String</span> <span class="op">=</span> <span class="ident">r</span>.<span class="ident">gen_ascii_chars</span>().<span class="ident">take</span>(<span class="number">100</span>).<span class="ident">collect</span>();
<span class="ident">r</span>.<span class="ident">reseed</span>((<span class="ident">ReseedWithDefault</span>, <span class="number">3</span>));
<span class="kw">let</span> <span class="ident">string2</span>: <span class="ident">String</span> <span class="op">=</span> <span class="ident">r</span>.<span class="ident">gen_ascii_chars</span>().<span class="ident">take</span>(<span class="number">100</span>).<span class="ident">collect</span>();
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">string1</span>, <span class="ident">string2</span>);
}
<span class="kw">const</span> <span class="ident">FILL_BYTES_V_LEN</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">13579</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_rng_fill_bytes</span>() {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span> <span class="op">=</span> <span class="ident">repeat</span>(<span class="number">0u8</span>).<span class="ident">take</span>(<span class="ident">FILL_BYTES_V_LEN</span>).<span class="ident">collect</span>::<span class="op"><</span><span class="ident">Vec</span><span class="op"><</span>_<span class="op">>></span>();
::<span class="ident">test</span>::<span class="ident">rng</span>().<span class="ident">fill_bytes</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">v</span>);
<span class="comment">// Sanity test: if we've gotten here, `fill_bytes` has not infinitely</span>
<span class="comment">// recursed.</span>
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">v</span>.<span class="ident">len</span>(), <span class="ident">FILL_BYTES_V_LEN</span>);
<span class="comment">// To test that `fill_bytes` actually did something, check that the</span>
<span class="comment">// average of `v` is not 0.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">sum</span> <span class="op">=</span> <span class="number">0.0</span>;
<span class="kw">for</span> <span class="kw-2">&</span><span class="ident">x</span> <span class="kw">in</span> <span class="ident">v</span>.<span class="ident">iter</span>() {
<span class="ident">sum</span> <span class="op">+=</span> <span class="ident">x</span> <span class="kw">as</span> <span class="ident">f64</span>;
}
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">sum</span> <span class="op">/</span> <span class="ident">v</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">f64</span> <span class="op">!=</span> <span class="number">0.0</span>);
}
}
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