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-// Copyright 2018 Developers of the Rand project.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! A small fast RNG
-
-use rand_core::{Error, RngCore, SeedableRng};
-
-#[cfg(all(not(target_os = "emscripten"), target_pointer_width = "64"))]
-type Rng = rand_pcg::Pcg64Mcg;
-#[cfg(not(all(not(target_os = "emscripten"), target_pointer_width = "64")))]
-type Rng = rand_pcg::Pcg32;
-
-/// A small-state, fast non-crypto PRNG
-///
-/// `SmallRng` may be a good choice when a PRNG with small state, cheap
-/// initialization, good statistical quality and good performance are required.
-/// It is **not** a good choice when security against prediction or
-/// reproducibility are important.
-///
-/// This PRNG is **feature-gated**: to use, you must enable the crate feature
-/// `small_rng`.
-///
-/// The algorithm is deterministic but should not be considered reproducible
-/// due to dependence on platform and possible replacement in future
-/// library versions. For a reproducible generator, use a named PRNG from an
-/// external crate, e.g. [rand_pcg] or [rand_chacha].
-/// Refer also to [The Book](https://rust-random.github.io/book/guide-rngs.html).
-///
-/// The PRNG algorithm in `SmallRng` is chosen to be
-/// efficient on the current platform, without consideration for cryptography
-/// or security. The size of its state is much smaller than [`StdRng`].
-/// The current algorithm is [`Pcg64Mcg`](rand_pcg::Pcg64Mcg) on 64-bit
-/// platforms and [`Pcg32`](rand_pcg::Pcg32) on 32-bit platforms. Both are
-/// implemented by the [rand_pcg] crate.
-///
-/// # Examples
-///
-/// Initializing `SmallRng` with a random seed can be done using [`SeedableRng::from_entropy`]:
-///
-/// ```
-/// use rand::{Rng, SeedableRng};
-/// use rand::rngs::SmallRng;
-///
-/// // Create small, cheap to initialize and fast RNG with a random seed.
-/// // The randomness is supplied by the operating system.
-/// let mut small_rng = SmallRng::from_entropy();
-/// # let v: u32 = small_rng.gen();
-/// ```
-///
-/// When initializing a lot of `SmallRng`'s, using [`thread_rng`] can be more
-/// efficient:
-///
-/// ```
-/// use rand::{SeedableRng, thread_rng};
-/// use rand::rngs::SmallRng;
-///
-/// // Create a big, expensive to initialize and slower, but unpredictable RNG.
-/// // This is cached and done only once per thread.
-/// let mut thread_rng = thread_rng();
-/// // Create small, cheap to initialize and fast RNGs with random seeds.
-/// // One can generally assume this won't fail.
-/// let rngs: Vec<SmallRng> = (0..10)
-/// .map(|_| SmallRng::from_rng(&mut thread_rng).unwrap())
-/// .collect();
-/// ```
-///
-/// [`StdRng`]: crate::rngs::StdRng
-/// [`thread_rng`]: crate::thread_rng
-/// [rand_chacha]: https://crates.io/crates/rand_chacha
-/// [rand_pcg]: https://crates.io/crates/rand_pcg
-#[derive(Clone, Debug)]
-pub struct SmallRng(Rng);
-
-impl RngCore for SmallRng {
- #[inline(always)]
- fn next_u32(&mut self) -> u32 {
- self.0.next_u32()
- }
-
- #[inline(always)]
- fn next_u64(&mut self) -> u64 {
- self.0.next_u64()
- }
-
- #[inline(always)]
- fn fill_bytes(&mut self, dest: &mut [u8]) {
- self.0.fill_bytes(dest);
- }
-
- #[inline(always)]
- fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
- self.0.try_fill_bytes(dest)
- }
-}
-
-impl SeedableRng for SmallRng {
- type Seed = <Rng as SeedableRng>::Seed;
-
- #[inline(always)]
- fn from_seed(seed: Self::Seed) -> Self {
- SmallRng(Rng::from_seed(seed))
- }
-
- #[inline(always)]
- fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error> {
- Rng::from_rng(rng).map(SmallRng)
- }
-}