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-rw-r--r--rand/src/prng/isaac.rs328
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diff --git a/rand/src/prng/isaac.rs b/rand/src/prng/isaac.rs
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-// Copyright 2013 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.
-
-//! The ISAAC random number generator.
-
-#![allow(non_camel_case_types)]
-
-use core::slice;
-use core::iter::repeat;
-use core::num::Wrapping as w;
-use core::fmt;
-
-use {Rng, SeedableRng, Rand};
-
-#[allow(bad_style)]
-type w32 = w<u32>;
-
-const RAND_SIZE_LEN: usize = 8;
-const RAND_SIZE: u32 = 1 << RAND_SIZE_LEN;
-const RAND_SIZE_USIZE: usize = 1 << RAND_SIZE_LEN;
-
-/// A random number generator that uses the ISAAC algorithm[1].
-///
-/// The ISAAC algorithm is generally accepted as suitable for
-/// cryptographic purposes, but this implementation has not be
-/// verified as such. Prefer a generator like `OsRng` that defers to
-/// the operating system for cases that need high security.
-///
-/// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
-/// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
-#[derive(Copy)]
-pub struct IsaacRng {
- cnt: u32,
- rsl: [w32; RAND_SIZE_USIZE],
- mem: [w32; RAND_SIZE_USIZE],
- a: w32,
- b: w32,
- c: w32,
-}
-
-static EMPTY: IsaacRng = IsaacRng {
- cnt: 0,
- rsl: [w(0); RAND_SIZE_USIZE],
- mem: [w(0); RAND_SIZE_USIZE],
- a: w(0), b: w(0), c: w(0),
-};
-
-impl IsaacRng {
-
- /// Create an ISAAC random number generator using the default
- /// fixed seed.
- pub fn new_unseeded() -> IsaacRng {
- let mut rng = EMPTY;
- rng.init(false);
- rng
- }
-
- /// Initialises `self`. If `use_rsl` is true, then use the current value
- /// of `rsl` as a seed, otherwise construct one algorithmically (not
- /// randomly).
- fn init(&mut self, use_rsl: bool) {
- let mut a = w(0x9e3779b9);
- let mut b = a;
- let mut c = a;
- let mut d = a;
- let mut e = a;
- let mut f = a;
- let mut g = a;
- let mut h = a;
-
- macro_rules! mix {
- () => {{
- a=a^(b<<11); d=d+a; b=b+c;
- b=b^(c>>2); e=e+b; c=c+d;
- c=c^(d<<8); f=f+c; d=d+e;
- d=d^(e>>16); g=g+d; e=e+f;
- e=e^(f<<10); h=h+e; f=f+g;
- f=f^(g>>4); a=a+f; g=g+h;
- g=g^(h<<8); b=b+g; h=h+a;
- h=h^(a>>9); c=c+h; a=a+b;
- }}
- }
-
- for _ in 0..4 {
- mix!();
- }
-
- if use_rsl {
- macro_rules! memloop {
- ($arr:expr) => {{
- for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
- a=a+$arr[i ]; b=b+$arr[i+1];
- c=c+$arr[i+2]; d=d+$arr[i+3];
- e=e+$arr[i+4]; f=f+$arr[i+5];
- g=g+$arr[i+6]; h=h+$arr[i+7];
- mix!();
- self.mem[i ]=a; self.mem[i+1]=b;
- self.mem[i+2]=c; self.mem[i+3]=d;
- self.mem[i+4]=e; self.mem[i+5]=f;
- self.mem[i+6]=g; self.mem[i+7]=h;
- }
- }}
- }
-
- memloop!(self.rsl);
- memloop!(self.mem);
- } else {
- for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
- mix!();
- self.mem[i ]=a; self.mem[i+1]=b;
- self.mem[i+2]=c; self.mem[i+3]=d;
- self.mem[i+4]=e; self.mem[i+5]=f;
- self.mem[i+6]=g; self.mem[i+7]=h;
- }
- }
-
- self.isaac();
- }
-
- /// Refills the output buffer (`self.rsl`)
- #[inline]
- fn isaac(&mut self) {
- self.c = self.c + w(1);
- // abbreviations
- let mut a = self.a;
- let mut b = self.b + self.c;
-
- const MIDPOINT: usize = RAND_SIZE_USIZE / 2;
-
- macro_rules! ind {
- ($x:expr) => ( self.mem[($x >> 2usize).0 as usize & (RAND_SIZE_USIZE - 1)] )
- }
-
- let r = [(0, MIDPOINT), (MIDPOINT, 0)];
- for &(mr_offset, m2_offset) in r.iter() {
-
- macro_rules! rngstepp {
- ($j:expr, $shift:expr) => {{
- let base = $j;
- let mix = a << $shift;
-
- let x = self.mem[base + mr_offset];
- a = (a ^ mix) + self.mem[base + m2_offset];
- let y = ind!(x) + a + b;
- self.mem[base + mr_offset] = y;
-
- b = ind!(y >> RAND_SIZE_LEN) + x;
- self.rsl[base + mr_offset] = b;
- }}
- }
-
- macro_rules! rngstepn {
- ($j:expr, $shift:expr) => {{
- let base = $j;
- let mix = a >> $shift;
-
- let x = self.mem[base + mr_offset];
- a = (a ^ mix) + self.mem[base + m2_offset];
- let y = ind!(x) + a + b;
- self.mem[base + mr_offset] = y;
-
- b = ind!(y >> RAND_SIZE_LEN) + x;
- self.rsl[base + mr_offset] = b;
- }}
- }
-
- for i in (0..MIDPOINT/4).map(|i| i * 4) {
- rngstepp!(i + 0, 13);
- rngstepn!(i + 1, 6);
- rngstepp!(i + 2, 2);
- rngstepn!(i + 3, 16);
- }
- }
-
- self.a = a;
- self.b = b;
- self.cnt = RAND_SIZE;
- }
-}
-
-// Cannot be derived because [u32; 256] does not implement Clone
-impl Clone for IsaacRng {
- fn clone(&self) -> IsaacRng {
- *self
- }
-}
-
-impl Rng for IsaacRng {
- #[inline]
- fn next_u32(&mut self) -> u32 {
- if self.cnt == 0 {
- // make some more numbers
- self.isaac();
- }
- self.cnt -= 1;
-
- // self.cnt is at most RAND_SIZE, but that is before the
- // subtraction above. We want to index without bounds
- // checking, but this could lead to incorrect code if someone
- // misrefactors, so we check, sometimes.
- //
- // (Changes here should be reflected in Isaac64Rng.next_u64.)
- debug_assert!(self.cnt < RAND_SIZE);
-
- // (the % is cheaply telling the optimiser that we're always
- // in bounds, without unsafe. NB. this is a power of two, so
- // it optimises to a bitwise mask).
- self.rsl[(self.cnt % RAND_SIZE) as usize].0
- }
-}
-
-impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
- fn reseed(&mut self, seed: &'a [u32]) {
- // make the seed into [seed[0], seed[1], ..., seed[seed.len()
- // - 1], 0, 0, ...], to fill rng.rsl.
- let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));
-
- for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
- *rsl_elem = w(seed_elem);
- }
- self.cnt = 0;
- self.a = w(0);
- self.b = w(0);
- self.c = w(0);
-
- self.init(true);
- }
-
- /// Create an ISAAC random number generator with a seed. This can
- /// be any length, although the maximum number of elements used is
- /// 256 and any more will be silently ignored. A generator
- /// constructed with a given seed will generate the same sequence
- /// of values as all other generators constructed with that seed.
- fn from_seed(seed: &'a [u32]) -> IsaacRng {
- let mut rng = EMPTY;
- rng.reseed(seed);
- rng
- }
-}
-
-impl Rand for IsaacRng {
- fn rand<R: Rng>(other: &mut R) -> IsaacRng {
- let mut ret = EMPTY;
- unsafe {
- let ptr = ret.rsl.as_mut_ptr() as *mut u8;
-
- let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_USIZE * 4);
- other.fill_bytes(slice);
- }
- ret.cnt = 0;
- ret.a = w(0);
- ret.b = w(0);
- ret.c = w(0);
-
- ret.init(true);
- return ret;
- }
-}
-
-impl fmt::Debug for IsaacRng {
- fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
- write!(f, "IsaacRng {{}}")
- }
-}
-
-#[cfg(test)]
-mod test {
- use {Rng, SeedableRng};
- use super::IsaacRng;
-
- #[test]
- fn test_rng_32_rand_seeded() {
- let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
- let mut ra: IsaacRng = SeedableRng::from_seed(&s[..]);
- let mut rb: IsaacRng = SeedableRng::from_seed(&s[..]);
- assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
- rb.gen_ascii_chars().take(100)));
- }
-
- #[test]
- fn test_rng_32_seeded() {
- let seed: &[_] = &[1, 23, 456, 7890, 12345];
- let mut ra: IsaacRng = SeedableRng::from_seed(seed);
- let mut rb: IsaacRng = SeedableRng::from_seed(seed);
- assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
- rb.gen_ascii_chars().take(100)));
- }
-
- #[test]
- fn test_rng_32_reseed() {
- let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
- let mut r: IsaacRng = SeedableRng::from_seed(&s[..]);
- let string1: String = r.gen_ascii_chars().take(100).collect();
-
- r.reseed(&s[..]);
-
- let string2: String = r.gen_ascii_chars().take(100).collect();
- assert_eq!(string1, string2);
- }
-
- #[test]
- fn test_rng_32_true_values() {
- let seed: &[_] = &[1, 23, 456, 7890, 12345];
- let mut ra: IsaacRng = SeedableRng::from_seed(seed);
- // Regression test that isaac is actually using the above vector
- let v = (0..10).map(|_| ra.next_u32()).collect::<Vec<_>>();
- assert_eq!(v,
- vec!(2558573138, 873787463, 263499565, 2103644246, 3595684709,
- 4203127393, 264982119, 2765226902, 2737944514, 3900253796));
-
- let seed: &[_] = &[12345, 67890, 54321, 9876];
- let mut rb: IsaacRng = SeedableRng::from_seed(seed);
- // skip forward to the 10000th number
- for _ in 0..10000 { rb.next_u32(); }
-
- let v = (0..10).map(|_| rb.next_u32()).collect::<Vec<_>>();
- assert_eq!(v,
- vec!(3676831399, 3183332890, 2834741178, 3854698763, 2717568474,
- 1576568959, 3507990155, 179069555, 141456972, 2478885421));
- }
-}
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