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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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