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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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