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| </pre><pre class="rust"><code><span class="comment">// Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License.. |
| |
| </span><span class="doccomment">//! A wrapper around another RNG that reseeds it after it |
| //! generates a certain number of random bytes. |
| |
| </span><span class="kw">use </span>std::default::Default; |
| |
| <span class="kw">use crate</span>::{Rng, SeedableRng}; |
| |
| <span class="doccomment">/// How many bytes of entropy the underling RNG is allowed to generate |
| /// before it is reseeded |
| </span><span class="kw">const </span>DEFAULT_GENERATION_THRESHOLD: u64 = <span class="number">32 </span>* <span class="number">1024</span>; |
| |
| <span class="doccomment">/// A wrapper around any RNG which reseeds the underlying RNG after it |
| /// has generated a certain number of random bytes. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub struct </span>ReseedingRng<R, Rsdr> { |
| rng: R, |
| generation_threshold: u64, |
| bytes_generated: u64, |
| <span class="doccomment">/// Controls the behaviour when reseeding the RNG. |
| </span><span class="kw">pub </span>reseeder: Rsdr, |
| } |
| |
| <span class="kw">impl</span><R: Rng, Rsdr: Reseeder<R>> ReseedingRng<R, Rsdr> { |
| <span class="doccomment">/// Create a new `ReseedingRng` with the given parameters. |
| /// |
| /// # Arguments |
| /// |
| /// * `rng`: the random number generator to use. |
| /// * `generation_threshold`: the number of bytes of entropy at which to reseed the RNG. |
| /// * `reseeder`: the reseeding object to use. |
| </span><span class="kw">pub fn </span>new(rng: R, generation_threshold: u64, reseeder: Rsdr) -> ReseedingRng<R, Rsdr> { |
| ReseedingRng { |
| rng, |
| generation_threshold, |
| bytes_generated: <span class="number">0</span>, |
| reseeder, |
| } |
| } |
| |
| <span class="doccomment">/// Reseed the internal RNG if the number of bytes that have been |
| /// generated exceed the threshold. |
| </span><span class="kw">pub fn </span>reseed_if_necessary(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">if </span><span class="self">self</span>.bytes_generated >= <span class="self">self</span>.generation_threshold { |
| <span class="self">self</span>.reseeder.reseed(<span class="kw-2">&mut </span><span class="self">self</span>.rng); |
| <span class="self">self</span>.bytes_generated = <span class="number">0</span>; |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><R: Rng, Rsdr: Reseeder<R>> Rng <span class="kw">for </span>ReseedingRng<R, Rsdr> { |
| <span class="kw">fn </span>next_u32(<span class="kw-2">&mut </span><span class="self">self</span>) -> u32 { |
| <span class="self">self</span>.reseed_if_necessary(); |
| <span class="self">self</span>.bytes_generated += <span class="number">4</span>; |
| <span class="self">self</span>.rng.next_u32() |
| } |
| |
| <span class="kw">fn </span>next_u64(<span class="kw-2">&mut </span><span class="self">self</span>) -> u64 { |
| <span class="self">self</span>.reseed_if_necessary(); |
| <span class="self">self</span>.bytes_generated += <span class="number">8</span>; |
| <span class="self">self</span>.rng.next_u64() |
| } |
| |
| <span class="kw">fn </span>fill_bytes(<span class="kw-2">&mut </span><span class="self">self</span>, dest: <span class="kw-2">&mut </span>[u8]) { |
| <span class="self">self</span>.reseed_if_necessary(); |
| <span class="self">self</span>.bytes_generated += dest.len() <span class="kw">as </span>u64; |
| <span class="self">self</span>.rng.fill_bytes(dest) |
| } |
| } |
| |
| <span class="kw">impl</span><S, R: SeedableRng<S>, Rsdr: Reseeder<R> + Default> SeedableRng<(Rsdr, S)> |
| <span class="kw">for </span>ReseedingRng<R, Rsdr> |
| { |
| <span class="kw">fn </span>reseed(<span class="kw-2">&mut </span><span class="self">self</span>, (rsdr, seed): (Rsdr, S)) { |
| <span class="self">self</span>.rng.reseed(seed); |
| <span class="self">self</span>.reseeder = rsdr; |
| <span class="self">self</span>.bytes_generated = <span class="number">0</span>; |
| } |
| |
| <span class="doccomment">/// Create a new `ReseedingRng` from the given reseeder and |
| /// seed. This uses a default value for `generation_threshold`. |
| </span><span class="kw">fn </span>from_seed((rsdr, seed): (Rsdr, S)) -> ReseedingRng<R, Rsdr> { |
| ReseedingRng { |
| rng: SeedableRng::from_seed(seed), |
| generation_threshold: DEFAULT_GENERATION_THRESHOLD, |
| bytes_generated: <span class="number">0</span>, |
| reseeder: rsdr, |
| } |
| } |
| } |
| |
| <span class="attribute">#[allow(clippy::needless_doctest_main)] |
| </span><span class="doccomment">/// Something that can be used to reseed an RNG via `ReseedingRng`. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// use sgx_rand::{Rng, SeedableRng, StdRng}; |
| /// use sgx_rand::reseeding::{Reseeder, ReseedingRng}; |
| /// |
| /// struct TickTockReseeder { tick: bool } |
| /// impl Reseeder<StdRng> for TickTockReseeder { |
| /// fn reseed(&mut self, rng: &mut StdRng) { |
| /// let val = if self.tick {0} else {1}; |
| /// rng.reseed(&[val]); |
| /// self.tick = !self.tick; |
| /// } |
| /// } |
| /// fn main() { |
| /// let rsdr = TickTockReseeder { tick: true }; |
| /// |
| /// let inner = StdRng::new().unwrap(); |
| /// let mut rng = ReseedingRng::new(inner, 10, rsdr); |
| /// |
| /// // this will repeat, because it gets reseeded very regularly. |
| /// let s: String = rng.gen_ascii_chars().take(100).collect(); |
| /// println!("{}", s); |
| /// } |
| /// |
| /// ``` |
| </span><span class="kw">pub trait </span>Reseeder<R> { |
| <span class="doccomment">/// Reseed the given RNG. |
| </span><span class="kw">fn </span>reseed(<span class="kw-2">&mut </span><span class="self">self</span>, rng: <span class="kw-2">&mut </span>R); |
| } |
| |
| <span class="doccomment">/// Reseed an RNG using a `Default` instance. This reseeds by |
| /// replacing the RNG with the result of a `Default::default` call. |
| </span><span class="attribute">#[derive(Clone, Copy, Debug)] |
| </span><span class="kw">pub struct </span>ReseedWithDefault; |
| |
| <span class="kw">impl</span><R: Rng + Default> Reseeder<R> <span class="kw">for </span>ReseedWithDefault { |
| <span class="kw">fn </span>reseed(<span class="kw-2">&mut </span><span class="self">self</span>, rng: <span class="kw-2">&mut </span>R) { |
| <span class="kw-2">*</span>rng = Default::default(); |
| } |
| } |
| <span class="kw">impl </span>Default <span class="kw">for </span>ReseedWithDefault { |
| <span class="kw">fn </span>default() -> ReseedWithDefault { |
| ReseedWithDefault |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="sgx_rand" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
