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Diffstat (limited to 'rand/src/rngs/small.rs')
| -rw-r--r-- | rand/src/rngs/small.rs | 115 |
1 files changed, 0 insertions, 115 deletions
diff --git a/rand/src/rngs/small.rs b/rand/src/rngs/small.rs deleted file mode 100644 index 6571363..0000000 --- a/rand/src/rngs/small.rs +++ /dev/null @@ -1,115 +0,0 @@ -// 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::{RngCore, SeedableRng, Error}; - -#[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 std::iter; -/// 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> = iter::repeat(()) -/// .map(|()| SmallRng::from_rng(&mut thread_rng).unwrap()) -/// .take(10) -/// .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) - } -} |