Struct rand::prng::Isaac64Rng

pub struct Isaac64Rng { /* fields omitted */ }

A random number generator that uses ISAAC-64, the 64-bit variant of the ISAAC algorithm.

ISAAC stands for "Indirection, Shift, Accumulate, Add, and Count" which are the principal bitwise operations employed. It is the most advanced of a series of array based random number generator designed by Robert Jenkins in 1996[1].

Although ISAAC is designed to be cryptographically secure, its design is not founded in cryptographic theory. Therefore it is not recommended for cryptographic purposes. It is however one of the strongest non-cryptograpic RNGs, and that while still being reasonably fast.

ISAAC-64 is mostly similar to ISAAC. Because it operates on 64-bit integers instead of 32-bit, it uses twice as much memory to hold its state and results. Also it uses different constants for shifts and indirect indexing, optimized to give good results for 64bit arithmetic.

Overview of the ISAAC-64 algorithm:

(in pseudo-code)

Input: a, b, c, s[256] // state
Output: r[256] // results

mix(a,i) = !(a ^ a << 21)  if i = 0 mod 4
             a ^ a >>  5   if i = 1 mod 4
             a ^ a << 12   if i = 2 mod 4
             a ^ a >> 33   if i = 3 mod 4

c = c + 1
b = b + c

for i in 0..256 {
    x = s_[i]
    a = mix(a,i) + s[i+128 mod 256]
    y = a + b + s[x>>3 mod 256]
    s[i] = y
    b = x + s[y>>11 mod 256]
    r[i] = b
}

See for more information the description in rand::prng::IsaacRng.

[1]: Bob Jenkins, ISAAC and RC4

Methods

impl Isaac64Rng

pub fn new_unseeded() -> Isaac64Rng

Deprecated since 0.5.0

: use the NewRng or SeedableRng trait

Create a 64-bit ISAAC random number generator using the default fixed seed.

DEPRECATED. Isaac64Rng::new_from_u64(0) will produce identical results.

pub fn new_from_u64(seed: u64) -> Isaac64Rng

Creates an ISAAC-64 random number generator using an u64 as seed. If seed == 0 this will produce the same stream of random numbers as the reference implementation when used unseeded.

Trait Implementations

impl Clone for Isaac64Rng

fn clone(&self) -> Isaac64Rng

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Isaac64Rng

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl RngCore for Isaac64Rng

fn next_u32(&mut self) -> u32

Return the next random u32.

fn next_u64(&mut self) -> u64

Return the next random u64.

fn fill_bytes(&mut self, dest: &mut [u8])

Fill dest with random data.

fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>

Fill dest entirely with random data.

impl SeedableRng for Isaac64Rng

type Seed = [u8; 32]

Seed type, which is restricted to types mutably-dereferencable as u8 arrays (we recommend [u8; N] for some N).

fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed.

fn from_rng<R: RngCore>(rng: R) -> Result<Self, Error>

Create a new PRNG seeded from another Rng.