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-rw-r--r--rand/src/prng/xorshift.rs101
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diff --git a/rand/src/prng/xorshift.rs b/rand/src/prng/xorshift.rs
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-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-//! Xorshift generators
-
-use core::num::Wrapping as w;
-use {Rng, SeedableRng, Rand};
-
-/// An Xorshift[1] random number
-/// generator.
-///
-/// The Xorshift algorithm is not suitable for cryptographic purposes
-/// but is very fast. If you do not know for sure that it fits your
-/// requirements, use a more secure one such as `IsaacRng` or `OsRng`.
-///
-/// [1]: Marsaglia, George (July 2003). ["Xorshift
-/// RNGs"](http://www.jstatsoft.org/v08/i14/paper). *Journal of
-/// Statistical Software*. Vol. 8 (Issue 14).
-#[allow(missing_copy_implementations)]
-#[derive(Clone, Debug)]
-pub struct XorShiftRng {
- x: w<u32>,
- y: w<u32>,
- z: w<u32>,
- w: w<u32>,
-}
-
-impl XorShiftRng {
- /// Creates a new XorShiftRng instance which is not seeded.
- ///
- /// The initial values of this RNG are constants, so all generators created
- /// by this function will yield the same stream of random numbers. It is
- /// highly recommended that this is created through `SeedableRng` instead of
- /// this function
- pub fn new_unseeded() -> XorShiftRng {
- XorShiftRng {
- x: w(0x193a6754),
- y: w(0xa8a7d469),
- z: w(0x97830e05),
- w: w(0x113ba7bb),
- }
- }
-}
-
-impl Rng for XorShiftRng {
- #[inline]
- fn next_u32(&mut self) -> u32 {
- let x = self.x;
- let t = x ^ (x << 11);
- self.x = self.y;
- self.y = self.z;
- self.z = self.w;
- let w_ = self.w;
- self.w = w_ ^ (w_ >> 19) ^ (t ^ (t >> 8));
- self.w.0
- }
-}
-
-impl SeedableRng<[u32; 4]> for XorShiftRng {
- /// Reseed an XorShiftRng. This will panic if `seed` is entirely 0.
- fn reseed(&mut self, seed: [u32; 4]) {
- assert!(!seed.iter().all(|&x| x == 0),
- "XorShiftRng.reseed called with an all zero seed.");
-
- self.x = w(seed[0]);
- self.y = w(seed[1]);
- self.z = w(seed[2]);
- self.w = w(seed[3]);
- }
-
- /// Create a new XorShiftRng. This will panic if `seed` is entirely 0.
- fn from_seed(seed: [u32; 4]) -> XorShiftRng {
- assert!(!seed.iter().all(|&x| x == 0),
- "XorShiftRng::from_seed called with an all zero seed.");
-
- XorShiftRng {
- x: w(seed[0]),
- y: w(seed[1]),
- z: w(seed[2]),
- w: w(seed[3]),
- }
- }
-}
-
-impl Rand for XorShiftRng {
- fn rand<R: Rng>(rng: &mut R) -> XorShiftRng {
- let mut tuple: (u32, u32, u32, u32) = rng.gen();
- while tuple == (0, 0, 0, 0) {
- tuple = rng.gen();
- }
- let (x, y, z, w_) = tuple;
- XorShiftRng { x: w(x), y: w(y), z: w(z), w: w(w_) }
- }
-}