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| <span id="517">517</span> |
| <span id="518">518</span> |
| <span id="519">519</span> |
| <span id="520">520</span> |
| <span id="521">521</span> |
| <span id="522">522</span> |
| <span id="523">523</span> |
| <span id="524">524</span> |
| <span id="525">525</span> |
| <span id="526">526</span> |
| <span id="527">527</span> |
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| <span id="529">529</span> |
| <span id="530">530</span> |
| <span id="531">531</span> |
| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project.</span> |
| <span class="comment">// Copyright 2017-2018 The Rust Project Developers.</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 generation traits</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! This crate is mainly of interest to crates publishing implementations of</span> |
| <span class="doccomment">//! [`RngCore`]. Other users are encouraged to use the [`rand`] crate instead</span> |
| <span class="doccomment">//! which re-exports the main traits and error types.</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! [`RngCore`] is the core trait implemented by algorithmic pseudo-random number</span> |
| <span class="doccomment">//! generators and external random-number sources.</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! [`SeedableRng`] is an extension trait for construction from fixed seeds and</span> |
| <span class="doccomment">//! other random number generators.</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! [`Error`] is provided for error-handling. It is safe to use in `no_std`</span> |
| <span class="doccomment">//! environments.</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! The [`impls`] and [`le`] sub-modules include a few small functions to assist</span> |
| <span class="doccomment">//! implementation of [`RngCore`].</span> |
| <span class="doccomment">//!</span> |
| <span class="doccomment">//! [`rand`]: https://docs.rs/rand</span> |
| |
| <span class="attribute">#![<span class="ident">doc</span>( |
| <span class="ident">html_logo_url</span> <span class="op">=</span> <span class="string">"https://www.rust-lang.org/logos/rust-logo-128x128-blk.png"</span>, |
| <span class="ident">html_favicon_url</span> <span class="op">=</span> <span class="string">"https://www.rust-lang.org/favicon.ico"</span>, |
| <span class="ident">html_root_url</span> <span class="op">=</span> <span class="string">"https://rust-random.github.io/rand/"</span> |
| )]</span> |
| <span class="attribute">#![<span class="ident">deny</span>(<span class="ident">missing_docs</span>)]</span> |
| <span class="attribute">#![<span class="ident">deny</span>(<span class="ident">missing_debug_implementations</span>)]</span> |
| <span class="attribute">#![<span class="ident">doc</span>(<span class="ident">test</span>(<span class="ident">attr</span>(<span class="ident">allow</span>(<span class="ident">unused_variables</span>), <span class="ident">deny</span>(<span class="ident">warnings</span>))))]</span> |
| <span class="attribute">#![<span class="ident">cfg_attr</span>(<span class="ident">doc_cfg</span>, <span class="ident">feature</span>(<span class="ident">doc_cfg</span>))]</span> |
| <span class="attribute">#![<span class="ident">no_std</span>]</span> |
| |
| <span class="kw">use</span> <span class="ident">core::convert::AsMut</span>; |
| <span class="kw">use</span> <span class="ident">core::default::Default</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">extern</span> <span class="kw">crate</span> <span class="ident">std</span>; |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"alloc"</span>)]</span> <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">alloc</span>; |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"alloc"</span>)]</span> <span class="kw">use</span> <span class="ident">alloc::boxed::Box</span>; |
| |
| <span class="kw">pub</span> <span class="kw">use</span> <span class="ident">error::Error</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">os::OsRng</span>; |
| |
| |
| <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">block</span>; |
| <span class="kw">mod</span> <span class="ident">error</span>; |
| <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">impls</span>; |
| <span class="kw">pub</span> <span class="kw">mod</span> <span class="ident">le</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">mod</span> <span class="ident">os</span>; |
| |
| |
| <span class="doccomment">/// The core of a random number generator.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This trait encapsulates the low-level functionality common to all</span> |
| <span class="doccomment">/// generators, and is the "back end", to be implemented by generators.</span> |
| <span class="doccomment">/// End users should normally use the `Rng` trait from the [`rand`] crate,</span> |
| <span class="doccomment">/// which is automatically implemented for every type implementing `RngCore`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Three different methods for generating random data are provided since the</span> |
| <span class="doccomment">/// optimal implementation of each is dependent on the type of generator. There</span> |
| <span class="doccomment">/// is no required relationship between the output of each; e.g. many</span> |
| <span class="doccomment">/// implementations of [`fill_bytes`] consume a whole number of `u32` or `u64`</span> |
| <span class="doccomment">/// values and drop any remaining unused bytes. The same can happen with the</span> |
| <span class="doccomment">/// [`next_u32`] and [`next_u64`] methods, implementations may discard some</span> |
| <span class="doccomment">/// random bits for efficiency.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// The [`try_fill_bytes`] method is a variant of [`fill_bytes`] allowing error</span> |
| <span class="doccomment">/// handling; it is not deemed sufficiently useful to add equivalents for</span> |
| <span class="doccomment">/// [`next_u32`] or [`next_u64`] since the latter methods are almost always used</span> |
| <span class="doccomment">/// with algorithmic generators (PRNGs), which are normally infallible.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Implementers should produce bits uniformly. Pathological RNGs (e.g. always</span> |
| <span class="doccomment">/// returning the same value, or never setting certain bits) can break rejection</span> |
| <span class="doccomment">/// sampling used by random distributions, and also break other RNGs when</span> |
| <span class="doccomment">/// seeding them via [`SeedableRng::from_rng`].</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Algorithmic generators implementing [`SeedableRng`] should normally have</span> |
| <span class="doccomment">/// *portable, reproducible* output, i.e. fix Endianness when converting values</span> |
| <span class="doccomment">/// to avoid platform differences, and avoid making any changes which affect</span> |
| <span class="doccomment">/// output (except by communicating that the release has breaking changes).</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Typically an RNG will implement only one of the methods available</span> |
| <span class="doccomment">/// in this trait directly, then use the helper functions from the</span> |
| <span class="doccomment">/// [`impls`] module to implement the other methods.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// It is recommended that implementations also implement:</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// - `Debug` with a custom implementation which *does not* print any internal</span> |
| <span class="doccomment">/// state (at least, [`CryptoRng`]s should not risk leaking state through</span> |
| <span class="doccomment">/// `Debug`).</span> |
| <span class="doccomment">/// - `Serialize` and `Deserialize` (from Serde), preferably making Serde</span> |
| <span class="doccomment">/// support optional at the crate level in PRNG libs.</span> |
| <span class="doccomment">/// - `Clone`, if possible.</span> |
| <span class="doccomment">/// - *never* implement `Copy` (accidental copies may cause repeated values).</span> |
| <span class="doccomment">/// - *do not* implement `Default` for pseudorandom generators, but instead</span> |
| <span class="doccomment">/// implement [`SeedableRng`], to guide users towards proper seeding.</span> |
| <span class="doccomment">/// External / hardware RNGs can choose to implement `Default`.</span> |
| <span class="doccomment">/// - `Eq` and `PartialEq` could be implemented, but are probably not useful.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Example</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// A simple example, obviously not generating very *random* output:</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">/// #![allow(dead_code)]</span> |
| <span class="doccomment">/// use rand_core::{RngCore, Error, impls};</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// struct CountingRng(u64);</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// impl RngCore for CountingRng {</span> |
| <span class="doccomment">/// fn next_u32(&mut self) -> u32 {</span> |
| <span class="doccomment">/// self.next_u64() as u32</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// fn next_u64(&mut self) -> u64 {</span> |
| <span class="doccomment">/// self.0 += 1;</span> |
| <span class="doccomment">/// self.0</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// fn fill_bytes(&mut self, dest: &mut [u8]) {</span> |
| <span class="doccomment">/// impls::fill_bytes_via_next(self, dest)</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {</span> |
| <span class="doccomment">/// Ok(self.fill_bytes(dest))</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`rand`]: https://docs.rs/rand</span> |
| <span class="doccomment">/// [`try_fill_bytes`]: RngCore::try_fill_bytes</span> |
| <span class="doccomment">/// [`fill_bytes`]: RngCore::fill_bytes</span> |
| <span class="doccomment">/// [`next_u32`]: RngCore::next_u32</span> |
| <span class="doccomment">/// [`next_u64`]: RngCore::next_u64</span> |
| <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">RngCore</span> { |
| <span class="doccomment">/// Return the next random `u32`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// RNGs must implement at least one method from this trait directly. In</span> |
| <span class="doccomment">/// the case this method is not implemented directly, it can be implemented</span> |
| <span class="doccomment">/// using `self.next_u64() as u32` or via [`impls::next_u32_via_fill`].</span> |
| <span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u32</span>; |
| |
| <span class="doccomment">/// Return the next random `u64`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// RNGs must implement at least one method from this trait directly. In</span> |
| <span class="doccomment">/// the case this method is not implemented directly, it can be implemented</span> |
| <span class="doccomment">/// via [`impls::next_u64_via_u32`] or via [`impls::next_u64_via_fill`].</span> |
| <span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u64</span>; |
| |
| <span class="doccomment">/// Fill `dest` with random data.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// RNGs must implement at least one method from this trait directly. In</span> |
| <span class="doccomment">/// the case this method is not implemented directly, it can be implemented</span> |
| <span class="doccomment">/// via [`impls::fill_bytes_via_next`] or</span> |
| <span class="doccomment">/// via [`RngCore::try_fill_bytes`]; if this generator can</span> |
| <span class="doccomment">/// fail the implementation must choose how best to handle errors here</span> |
| <span class="doccomment">/// (e.g. panic with a descriptive message or log a warning and retry a few</span> |
| <span class="doccomment">/// times).</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This method should guarantee that `dest` is entirely filled</span> |
| <span class="doccomment">/// with new data, and may panic if this is impossible</span> |
| <span class="doccomment">/// (e.g. reading past the end of a file that is being used as the</span> |
| <span class="doccomment">/// source of randomness).</span> |
| <span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]); |
| |
| <span class="doccomment">/// Fill `dest` entirely with random data.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This is the only method which allows an RNG to report errors while</span> |
| <span class="doccomment">/// generating random data thus making this the primary method implemented</span> |
| <span class="doccomment">/// by external (true) RNGs (e.g. `OsRng`) which can fail. It may be used</span> |
| <span class="doccomment">/// directly to generate keys and to seed (infallible) PRNGs.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Other than error handling, this method is identical to [`RngCore::fill_bytes`];</span> |
| <span class="doccomment">/// thus this may be implemented using `Ok(self.fill_bytes(dest))` or</span> |
| <span class="doccomment">/// `fill_bytes` may be implemented with</span> |
| <span class="doccomment">/// `self.try_fill_bytes(dest).unwrap()` or more specific error handling.</span> |
| <span class="kw">fn</span> <span class="ident">try_fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Error</span><span class="op">></span>; |
| } |
| |
| <span class="doccomment">/// A marker trait used to indicate that an [`RngCore`] or [`BlockRngCore`]</span> |
| <span class="doccomment">/// implementation is supposed to be cryptographically secure.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// *Cryptographically secure generators*, also known as *CSPRNGs*, should</span> |
| <span class="doccomment">/// satisfy an additional properties over other generators: given the first</span> |
| <span class="doccomment">/// *k* bits of an algorithm's output</span> |
| <span class="doccomment">/// sequence, it should not be possible using polynomial-time algorithms to</span> |
| <span class="doccomment">/// predict the next bit with probability significantly greater than 50%.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Some generators may satisfy an additional property, however this is not</span> |
| <span class="doccomment">/// required by this trait: if the CSPRNG's state is revealed, it should not be</span> |
| <span class="doccomment">/// computationally-feasible to reconstruct output prior to this. Some other</span> |
| <span class="doccomment">/// generators allow backwards-computation and are considered *reversible*.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Note that this trait is provided for guidance only and cannot guarantee</span> |
| <span class="doccomment">/// suitability for cryptographic applications. In general it should only be</span> |
| <span class="doccomment">/// implemented for well-reviewed code implementing well-regarded algorithms.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Note also that use of a `CryptoRng` does not protect against other</span> |
| <span class="doccomment">/// weaknesses such as seeding from a weak entropy source or leaking state.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`BlockRngCore`]: block::BlockRngCore</span> |
| <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">CryptoRng</span> {} |
| |
| <span class="doccomment">/// An extension trait that is automatically implemented for any type</span> |
| <span class="doccomment">/// implementing [`RngCore`] and [`CryptoRng`].</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// It may be used as a trait object, and supports upcasting to [`RngCore`] via</span> |
| <span class="doccomment">/// the [`CryptoRngCore::as_rngcore`] method.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Example</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">/// use rand_core::CryptoRngCore;</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// #[allow(unused)]</span> |
| <span class="doccomment">/// fn make_token(rng: &mut dyn CryptoRngCore) -> [u8; 32] {</span> |
| <span class="doccomment">/// let mut buf = [0u8; 32];</span> |
| <span class="doccomment">/// rng.fill_bytes(&mut buf);</span> |
| <span class="doccomment">/// buf</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">CryptoRngCore</span>: <span class="ident">RngCore</span> { |
| <span class="doccomment">/// Upcast to an [`RngCore`] trait object.</span> |
| <span class="kw">fn</span> <span class="ident">as_rngcore</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="kw-2">&mut</span> <span class="kw">dyn</span> <span class="ident">RngCore</span>; |
| } |
| |
| <span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">CryptoRng</span> <span class="op">+</span> <span class="ident">RngCore</span><span class="op">></span> <span class="ident">CryptoRngCore</span> <span class="kw">for</span> <span class="ident">T</span> { |
| <span class="kw">fn</span> <span class="ident">as_rngcore</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="kw-2">&mut</span> <span class="kw">dyn</span> <span class="ident">RngCore</span> { |
| <span class="self">self</span> |
| } |
| } |
| |
| <span class="doccomment">/// A random number generator that can be explicitly seeded.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This trait encapsulates the low-level functionality common to all</span> |
| <span class="doccomment">/// pseudo-random number generators (PRNGs, or algorithmic generators).</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`rand`]: https://docs.rs/rand</span> |
| <span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">SeedableRng</span>: <span class="ident">Sized</span> { |
| <span class="doccomment">/// Seed type, which is restricted to types mutably-dereferenceable as `u8`</span> |
| <span class="doccomment">/// arrays (we recommend `[u8; N]` for some `N`).</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// It is recommended to seed PRNGs with a seed of at least circa 100 bits,</span> |
| <span class="doccomment">/// which means an array of `[u8; 12]` or greater to avoid picking RNGs with</span> |
| <span class="doccomment">/// partially overlapping periods.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// For cryptographic RNG's a seed of 256 bits is recommended, `[u8; 32]`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Implementing `SeedableRng` for RNGs with large seeds</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Note that the required traits `core::default::Default` and</span> |
| <span class="doccomment">/// `core::convert::AsMut<u8>` are not implemented for large arrays</span> |
| <span class="doccomment">/// `[u8; N]` with `N` > 32. To be able to implement the traits required by</span> |
| <span class="doccomment">/// `SeedableRng` for RNGs with such large seeds, the newtype pattern can be</span> |
| <span class="doccomment">/// used:</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// ```</span> |
| <span class="doccomment">/// use rand_core::SeedableRng;</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// const N: usize = 64;</span> |
| <span class="doccomment">/// pub struct MyRngSeed(pub [u8; N]);</span> |
| <span class="doccomment">/// pub struct MyRng(MyRngSeed);</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// impl Default for MyRngSeed {</span> |
| <span class="doccomment">/// fn default() -> MyRngSeed {</span> |
| <span class="doccomment">/// MyRngSeed([0; N])</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// impl AsMut<[u8]> for MyRngSeed {</span> |
| <span class="doccomment">/// fn as_mut(&mut self) -> &mut [u8] {</span> |
| <span class="doccomment">/// &mut self.0</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// impl SeedableRng for MyRng {</span> |
| <span class="doccomment">/// type Seed = MyRngSeed;</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// fn from_seed(seed: MyRngSeed) -> MyRng {</span> |
| <span class="doccomment">/// MyRng(seed)</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// }</span> |
| <span class="doccomment">/// ```</span> |
| <span class="kw">type</span> <span class="ident">Seed</span>: <span class="ident">Sized</span> <span class="op">+</span> <span class="ident">Default</span> <span class="op">+</span> <span class="ident">AsMut</span><span class="op"><</span>[<span class="ident">u8</span>]<span class="op">></span>; |
| |
| <span class="doccomment">/// Create a new PRNG using the given seed.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// PRNG implementations are allowed to assume that bits in the seed are</span> |
| <span class="doccomment">/// well distributed. That means usually that the number of one and zero</span> |
| <span class="doccomment">/// bits are roughly equal, and values like 0, 1 and (size - 1) are unlikely.</span> |
| <span class="doccomment">/// Note that many non-cryptographic PRNGs will show poor quality output</span> |
| <span class="doccomment">/// if this is not adhered to. If you wish to seed from simple numbers, use</span> |
| <span class="doccomment">/// `seed_from_u64` instead.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// All PRNG implementations should be reproducible unless otherwise noted:</span> |
| <span class="doccomment">/// given a fixed `seed`, the same sequence of output should be produced</span> |
| <span class="doccomment">/// on all runs, library versions and architectures (e.g. check endianness).</span> |
| <span class="doccomment">/// Any "value-breaking" changes to the generator should require bumping at</span> |
| <span class="doccomment">/// least the minor version and documentation of the change.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// It is not required that this function yield the same state as a</span> |
| <span class="doccomment">/// reference implementation of the PRNG given equivalent seed; if necessary</span> |
| <span class="doccomment">/// another constructor replicating behaviour from a reference</span> |
| <span class="doccomment">/// implementation can be added.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// PRNG implementations should make sure `from_seed` never panics. In the</span> |
| <span class="doccomment">/// case that some special values (like an all zero seed) are not viable</span> |
| <span class="doccomment">/// seeds it is preferable to map these to alternative constant value(s),</span> |
| <span class="doccomment">/// for example `0xBAD5EEDu32` or `0x0DDB1A5E5BAD5EEDu64` ("odd biases? bad</span> |
| <span class="doccomment">/// seed"). This is assuming only a small number of values must be rejected.</span> |
| <span class="kw">fn</span> <span class="ident">from_seed</span>(<span class="ident">seed</span>: <span class="ident"><span class="self">Self</span>::Seed</span>) -> <span class="self">Self</span>; |
| |
| <span class="doccomment">/// Create a new PRNG using a `u64` seed.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This is a convenience-wrapper around `from_seed` to allow construction</span> |
| <span class="doccomment">/// of any `SeedableRng` from a simple `u64` value. It is designed such that</span> |
| <span class="doccomment">/// low Hamming Weight numbers like 0 and 1 can be used and should still</span> |
| <span class="doccomment">/// result in good, independent seeds to the PRNG which is returned.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This **is not suitable for cryptography**, as should be clear given that</span> |
| <span class="doccomment">/// the input size is only 64 bits.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Implementations for PRNGs *may* provide their own implementations of</span> |
| <span class="doccomment">/// this function, but the default implementation should be good enough for</span> |
| <span class="doccomment">/// all purposes. *Changing* the implementation of this function should be</span> |
| <span class="doccomment">/// considered a value-breaking change.</span> |
| <span class="kw">fn</span> <span class="ident">seed_from_u64</span>(<span class="kw-2">mut</span> <span class="ident">state</span>: <span class="ident">u64</span>) -> <span class="self">Self</span> { |
| <span class="comment">// We use PCG32 to generate a u32 sequence, and copy to the seed</span> |
| <span class="kw">fn</span> <span class="ident">pcg32</span>(<span class="ident">state</span>: <span class="kw-2">&mut</span> <span class="ident">u64</span>) -> [<span class="ident">u8</span>; <span class="number">4</span>] { |
| <span class="kw">const</span> <span class="ident">MUL</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">6364136223846793005</span>; |
| <span class="kw">const</span> <span class="ident">INC</span>: <span class="ident">u64</span> <span class="op">=</span> <span class="number">11634580027462260723</span>; |
| |
| <span class="comment">// We advance the state first (to get away from the input value,</span> |
| <span class="comment">// in case it has low Hamming Weight).</span> |
| <span class="kw-2">*</span><span class="ident">state</span> <span class="op">=</span> <span class="ident">state</span>.<span class="ident">wrapping_mul</span>(<span class="ident">MUL</span>).<span class="ident">wrapping_add</span>(<span class="ident">INC</span>); |
| <span class="kw">let</span> <span class="ident">state</span> <span class="op">=</span> <span class="kw-2">*</span><span class="ident">state</span>; |
| |
| <span class="comment">// Use PCG output function with to_le to generate x:</span> |
| <span class="kw">let</span> <span class="ident">xorshifted</span> <span class="op">=</span> (((<span class="ident">state</span> <span class="op">></span><span class="op">></span> <span class="number">18</span>) <span class="op">^</span> <span class="ident">state</span>) <span class="op">></span><span class="op">></span> <span class="number">27</span>) <span class="kw">as</span> <span class="ident">u32</span>; |
| <span class="kw">let</span> <span class="ident">rot</span> <span class="op">=</span> (<span class="ident">state</span> <span class="op">></span><span class="op">></span> <span class="number">59</span>) <span class="kw">as</span> <span class="ident">u32</span>; |
| <span class="kw">let</span> <span class="ident">x</span> <span class="op">=</span> <span class="ident">xorshifted</span>.<span class="ident">rotate_right</span>(<span class="ident">rot</span>); |
| <span class="ident">x</span>.<span class="ident">to_le_bytes</span>() |
| } |
| |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">seed</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::Seed::default</span>(); |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">iter</span> <span class="op">=</span> <span class="ident">seed</span>.<span class="ident">as_mut</span>().<span class="ident">chunks_exact_mut</span>(<span class="number">4</span>); |
| <span class="kw">for</span> <span class="ident">chunk</span> <span class="kw">in</span> <span class="kw-2">&mut</span> <span class="ident">iter</span> { |
| <span class="ident">chunk</span>.<span class="ident">copy_from_slice</span>(<span class="kw-2">&</span><span class="ident">pcg32</span>(<span class="kw-2">&mut</span> <span class="ident">state</span>)); |
| } |
| <span class="kw">let</span> <span class="ident">rem</span> <span class="op">=</span> <span class="ident">iter</span>.<span class="ident">into_remainder</span>(); |
| <span class="kw">if</span> <span class="op">!</span><span class="ident">rem</span>.<span class="ident">is_empty</span>() { |
| <span class="ident">rem</span>.<span class="ident">copy_from_slice</span>(<span class="kw-2">&</span><span class="ident">pcg32</span>(<span class="kw-2">&mut</span> <span class="ident">state</span>)[..<span class="ident">rem</span>.<span class="ident">len</span>()]); |
| } |
| |
| <span class="ident"><span class="self">Self</span>::from_seed</span>(<span class="ident">seed</span>) |
| } |
| |
| <span class="doccomment">/// Create a new PRNG seeded from another `Rng`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This may be useful when needing to rapidly seed many PRNGs from a master</span> |
| <span class="doccomment">/// PRNG, and to allow forking of PRNGs. It may be considered deterministic.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// The master PRNG should be at least as high quality as the child PRNGs.</span> |
| <span class="doccomment">/// When seeding non-cryptographic child PRNGs, we recommend using a</span> |
| <span class="doccomment">/// different algorithm for the master PRNG (ideally a CSPRNG) to avoid</span> |
| <span class="doccomment">/// correlations between the child PRNGs. If this is not possible (e.g.</span> |
| <span class="doccomment">/// forking using small non-crypto PRNGs) ensure that your PRNG has a good</span> |
| <span class="doccomment">/// mixing function on the output or consider use of a hash function with</span> |
| <span class="doccomment">/// `from_seed`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// Note that seeding `XorShiftRng` from another `XorShiftRng` provides an</span> |
| <span class="doccomment">/// extreme example of what can go wrong: the new PRNG will be a clone</span> |
| <span class="doccomment">/// of the parent.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// PRNG implementations are allowed to assume that a good RNG is provided</span> |
| <span class="doccomment">/// for seeding, and that it is cryptographically secure when appropriate.</span> |
| <span class="doccomment">/// As of `rand` 0.7 / `rand_core` 0.5, implementations overriding this</span> |
| <span class="doccomment">/// method should ensure the implementation satisfies reproducibility</span> |
| <span class="doccomment">/// (in prior versions this was not required).</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`rand`]: https://docs.rs/rand</span> |
| <span class="kw">fn</span> <span class="ident">from_rng</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">RngCore</span><span class="op">></span>(<span class="kw-2">mut</span> <span class="ident">rng</span>: <span class="ident">R</span>) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="self">Self</span>, <span class="ident">Error</span><span class="op">></span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">seed</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::Seed::default</span>(); |
| <span class="ident">rng</span>.<span class="ident">try_fill_bytes</span>(<span class="ident">seed</span>.<span class="ident">as_mut</span>())<span class="question-mark">?</span>; |
| <span class="prelude-val">Ok</span>(<span class="ident"><span class="self">Self</span>::from_seed</span>(<span class="ident">seed</span>)) |
| } |
| |
| <span class="doccomment">/// Creates a new instance of the RNG seeded via [`getrandom`].</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// This method is the recommended way to construct non-deterministic PRNGs</span> |
| <span class="doccomment">/// since it is convenient and secure.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// In case the overhead of using [`getrandom`] to seed *many* PRNGs is an</span> |
| <span class="doccomment">/// issue, one may prefer to seed from a local PRNG, e.g.</span> |
| <span class="doccomment">/// `from_rng(thread_rng()).unwrap()`.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// # Panics</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// If [`getrandom`] is unable to provide secure entropy this method will panic.</span> |
| <span class="doccomment">///</span> |
| <span class="doccomment">/// [`getrandom`]: https://docs.rs/getrandom</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="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="kw">fn</span> <span class="ident">from_entropy</span>() -> <span class="self">Self</span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">seed</span> <span class="op">=</span> <span class="ident"><span class="self">Self</span>::Seed::default</span>(); |
| <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span> <span class="ident">getrandom::getrandom</span>(<span class="ident">seed</span>.<span class="ident">as_mut</span>()) { |
| <span class="macro">panic!</span>(<span class="string">"from_entropy failed: {}"</span>, <span class="ident">err</span>); |
| } |
| <span class="ident"><span class="self">Self</span>::from_seed</span>(<span class="ident">seed</span>) |
| } |
| } |
| |
| <span class="comment">// Implement `RngCore` for references to an `RngCore`.</span> |
| <span class="comment">// Force inlining all functions, so that it is up to the `RngCore`</span> |
| <span class="comment">// implementation and the optimizer to decide on inlining.</span> |
| <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">R</span>: <span class="ident">RngCore</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">RngCore</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">R</span> { |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u32</span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">next_u32</span>() |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u64</span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">next_u64</span>() |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">fill_bytes</span>(<span class="ident">dest</span>) |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">try_fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Error</span><span class="op">></span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">try_fill_bytes</span>(<span class="ident">dest</span>) |
| } |
| } |
| |
| <span class="comment">// Implement `RngCore` for boxed references to an `RngCore`.</span> |
| <span class="comment">// Force inlining all functions, so that it is up to the `RngCore`</span> |
| <span class="comment">// implementation and the optimizer to decide on inlining.</span> |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"alloc"</span>)]</span> |
| <span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">RngCore</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">RngCore</span> <span class="kw">for</span> <span class="ident">Box</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> { |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">next_u32</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u32</span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">next_u32</span>() |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">next_u64</span>(<span class="kw-2">&mut</span> <span class="self">self</span>) -> <span class="ident">u64</span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">next_u64</span>() |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">fill_bytes</span>(<span class="ident">dest</span>) |
| } |
| |
| <span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span> |
| <span class="kw">fn</span> <span class="ident">try_fill_bytes</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">dest</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) -> <span class="prelude-ty">Result</span><span class="op"><</span>(), <span class="ident">Error</span><span class="op">></span> { |
| (<span class="kw-2">*</span><span class="kw-2">*</span><span class="self">self</span>).<span class="ident">try_fill_bytes</span>(<span class="ident">dest</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">impl</span> <span class="ident">std::io::Read</span> <span class="kw">for</span> <span class="kw">dyn</span> <span class="ident">RngCore</span> { |
| <span class="kw">fn</span> <span class="ident">read</span>(<span class="kw-2">&mut</span> <span class="self">self</span>, <span class="ident">buf</span>: <span class="kw-2">&mut</span> [<span class="ident">u8</span>]) -> <span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">usize</span>, <span class="ident">std::io::Error</span><span class="op">></span> { |
| <span class="self">self</span>.<span class="ident">try_fill_bytes</span>(<span class="ident">buf</span>)<span class="question-mark">?</span>; |
| <span class="prelude-val">Ok</span>(<span class="ident">buf</span>.<span class="ident">len</span>()) |
| } |
| } |
| |
| <span class="comment">// Implement `CryptoRng` for references to a `CryptoRng`.</span> |
| <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">R</span>: <span class="ident">CryptoRng</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">CryptoRng</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="kw-2">mut</span> <span class="ident">R</span> {} |
| |
| <span class="comment">// Implement `CryptoRng` for boxed references to a `CryptoRng`.</span> |
| <span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"alloc"</span>)]</span> |
| <span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">CryptoRng</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span> <span class="ident">CryptoRng</span> <span class="kw">for</span> <span class="ident">Box</span><span class="op"><</span><span class="ident">R</span><span class="op">></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="kw">super</span>::<span class="kw-2">*</span>; |
| |
| <span class="attribute">#[<span class="ident">test</span>]</span> |
| <span class="kw">fn</span> <span class="ident">test_seed_from_u64</span>() { |
| <span class="kw">struct</span> <span class="ident">SeedableNum</span>(<span class="ident">u64</span>); |
| <span class="kw">impl</span> <span class="ident">SeedableRng</span> <span class="kw">for</span> <span class="ident">SeedableNum</span> { |
| <span class="kw">type</span> <span class="ident">Seed</span> <span class="op">=</span> [<span class="ident">u8</span>; <span class="number">8</span>]; |
| |
| <span class="kw">fn</span> <span class="ident">from_seed</span>(<span class="ident">seed</span>: <span class="ident"><span class="self">Self</span>::Seed</span>) -> <span class="self">Self</span> { |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> [<span class="number">0u64</span>; <span class="number">1</span>]; |
| <span class="ident">le::read_u64_into</span>(<span class="kw-2">&</span><span class="ident">seed</span>, <span class="kw-2">&mut</span> <span class="ident">x</span>); |
| <span class="ident">SeedableNum</span>(<span class="ident">x</span>[<span class="number">0</span>]) |
| } |
| } |
| |
| <span class="kw">const</span> <span class="ident">N</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">8</span>; |
| <span class="kw">const</span> <span class="ident">SEEDS</span>: [<span class="ident">u64</span>; <span class="ident">N</span>] <span class="op">=</span> [<span class="number">0u64</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">8</span>, <span class="number">16</span>, <span class="op">-</span><span class="number">1i64</span> <span class="kw">as</span> <span class="ident">u64</span>]; |
| <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">results</span> <span class="op">=</span> [<span class="number">0u64</span>; <span class="ident">N</span>]; |
| <span class="kw">for</span> (<span class="ident">i</span>, <span class="ident">seed</span>) <span class="kw">in</span> <span class="ident">SEEDS</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() { |
| <span class="kw">let</span> <span class="ident">SeedableNum</span>(<span class="ident">x</span>) <span class="op">=</span> <span class="ident">SeedableNum::seed_from_u64</span>(<span class="kw-2">*</span><span class="ident">seed</span>); |
| <span class="ident">results</span>[<span class="ident">i</span>] <span class="op">=</span> <span class="ident">x</span>; |
| } |
| |
| <span class="kw">for</span> (<span class="ident">i1</span>, <span class="ident">r1</span>) <span class="kw">in</span> <span class="ident">results</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() { |
| <span class="kw">let</span> <span class="ident">weight</span> <span class="op">=</span> <span class="ident">r1</span>.<span class="ident">count_ones</span>(); |
| <span class="comment">// This is the binomial distribution B(64, 0.5), so chance of</span> |
| <span class="comment">// weight < 20 is binocdf(19, 64, 0.5) = 7.8e-4, and same for</span> |
| <span class="comment">// weight > 44.</span> |
| <span class="macro">assert!</span>((<span class="number">20</span>..<span class="op">=</span><span class="number">44</span>).<span class="ident">contains</span>(<span class="kw-2">&</span><span class="ident">weight</span>)); |
| |
| <span class="kw">for</span> (<span class="ident">i2</span>, <span class="ident">r2</span>) <span class="kw">in</span> <span class="ident">results</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() { |
| <span class="kw">if</span> <span class="ident">i1</span> <span class="op">==</span> <span class="ident">i2</span> { |
| <span class="kw">continue</span>; |
| } |
| <span class="kw">let</span> <span class="ident">diff_weight</span> <span class="op">=</span> (<span class="ident">r1</span> <span class="op">^</span> <span class="ident">r2</span>).<span class="ident">count_ones</span>(); |
| <span class="macro">assert!</span>(<span class="ident">diff_weight</span> <span class="op">></span><span class="op">=</span> <span class="number">20</span>); |
| } |
| } |
| |
| <span class="comment">// value-breakage test:</span> |
| <span class="macro">assert_eq!</span>(<span class="ident">results</span>[<span class="number">0</span>], <span class="number">5029875928683246316</span>); |
| } |
| } |
| </code></pre></div> |
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