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Diffstat (limited to 'vendor/rand/src/rngs/xoshiro128plusplus.rs')
-rw-r--r-- | vendor/rand/src/rngs/xoshiro128plusplus.rs | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/vendor/rand/src/rngs/xoshiro128plusplus.rs b/vendor/rand/src/rngs/xoshiro128plusplus.rs new file mode 100644 index 000000000..ece98fafd --- /dev/null +++ b/vendor/rand/src/rngs/xoshiro128plusplus.rs @@ -0,0 +1,118 @@ +// 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. + +#[cfg(feature="serde1")] use serde::{Serialize, Deserialize}; +use rand_core::impls::{next_u64_via_u32, fill_bytes_via_next}; +use rand_core::le::read_u32_into; +use rand_core::{SeedableRng, RngCore, Error}; + +/// A xoshiro128++ random number generator. +/// +/// The xoshiro128++ algorithm is not suitable for cryptographic purposes, but +/// is very fast and has excellent statistical properties. +/// +/// The algorithm used here is translated from [the `xoshiro128plusplus.c` +/// reference source code](http://xoshiro.di.unimi.it/xoshiro128plusplus.c) by +/// David Blackman and Sebastiano Vigna. +#[derive(Debug, Clone, PartialEq, Eq)] +#[cfg_attr(feature="serde1", derive(Serialize, Deserialize))] +pub struct Xoshiro128PlusPlus { + s: [u32; 4], +} + +impl SeedableRng for Xoshiro128PlusPlus { + type Seed = [u8; 16]; + + /// Create a new `Xoshiro128PlusPlus`. If `seed` is entirely 0, it will be + /// mapped to a different seed. + #[inline] + fn from_seed(seed: [u8; 16]) -> Xoshiro128PlusPlus { + if seed.iter().all(|&x| x == 0) { + return Self::seed_from_u64(0); + } + let mut state = [0; 4]; + read_u32_into(&seed, &mut state); + Xoshiro128PlusPlus { s: state } + } + + /// Create a new `Xoshiro128PlusPlus` from a `u64` seed. + /// + /// This uses the SplitMix64 generator internally. + fn seed_from_u64(mut state: u64) -> Self { + const PHI: u64 = 0x9e3779b97f4a7c15; + let mut seed = Self::Seed::default(); + for chunk in seed.as_mut().chunks_mut(8) { + state = state.wrapping_add(PHI); + let mut z = state; + z = (z ^ (z >> 30)).wrapping_mul(0xbf58476d1ce4e5b9); + z = (z ^ (z >> 27)).wrapping_mul(0x94d049bb133111eb); + z = z ^ (z >> 31); + chunk.copy_from_slice(&z.to_le_bytes()); + } + Self::from_seed(seed) + } +} + +impl RngCore for Xoshiro128PlusPlus { + #[inline] + fn next_u32(&mut self) -> u32 { + let result_starstar = self.s[0] + .wrapping_add(self.s[3]) + .rotate_left(7) + .wrapping_add(self.s[0]); + + let t = self.s[1] << 9; + + self.s[2] ^= self.s[0]; + self.s[3] ^= self.s[1]; + self.s[1] ^= self.s[2]; + self.s[0] ^= self.s[3]; + + self.s[2] ^= t; + + self.s[3] = self.s[3].rotate_left(11); + + result_starstar + } + + #[inline] + fn next_u64(&mut self) -> u64 { + next_u64_via_u32(self) + } + + #[inline] + fn fill_bytes(&mut self, dest: &mut [u8]) { + fill_bytes_via_next(self, dest); + } + + #[inline] + fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { + self.fill_bytes(dest); + Ok(()) + } +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn reference() { + let mut rng = Xoshiro128PlusPlus::from_seed( + [1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0]); + // These values were produced with the reference implementation: + // http://xoshiro.di.unimi.it/xoshiro128plusplus.c + let expected = [ + 641, 1573767, 3222811527, 3517856514, 836907274, 4247214768, + 3867114732, 1355841295, 495546011, 621204420, + ]; + for &e in &expected { + assert_eq!(rng.next_u32(), e); + } + } +} |