[−][src]Struct rand::prng::isaac::IsaacRng
A random number generator that uses 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 199612.
ISAAC is notably fast and produces excellent quality random numbers for non-cryptographic applications.
In spite of being designed with cryptographic security in mind, ISAAC hasn't
been stringently cryptanalyzed and thus cryptographers do not not
consensually trust it to be secure. When looking for a secure RNG, prefer
Hc128Rng
instead, which, like ISAAC, is an array-based RNG and one of
the stream-ciphers selected the by eSTREAM contest.
In 2006 an improvement to ISAAC was suggested by Jean-Philippe Aumasson, named ISAAC+3. But because the specification is not complete, because there is no good implementation, and because the suggested bias may not exist, it is not implemented here.
Overview of the ISAAC algorithm:
(in pseudo-code)
Input: a, b, c, s[256] // state
Output: r[256] // results
mix(a,i) = a ^ a << 13 if i = 0 mod 4
a ^ a >> 6 if i = 1 mod 4
a ^ a << 2 if i = 2 mod 4
a ^ a >> 16 if i = 3 mod 4
c = c + 1
b = b + c
for i in 0..256 {
x = s_[i]
a = f(a,i) + s[i+128 mod 256]
y = a + b + s[x>>2 mod 256]
s[i] = y
b = x + s[y>>10 mod 256]
r[i] = b
}
Numbers are generated in blocks of 256. This means the function above only runs once every 256 times you ask for a next random number. In all other circumstances the last element of the results array is returned.
ISAAC therefore needs a lot of memory, relative to other non-crypto RNGs. 2 * 256 * 4 = 2 kb to hold the state and results.
This implementation uses BlockRng
to implement the RngCore
methods.
References
-
Bob Jenkins, ISAAC: A fast cryptographic random number generator ↩
-
Bob Jenkins, ISAAC and RC4 ↩
-
Jean-Philippe Aumasson, On the pseudo-random generator ISAAC ↩
Methods
impl IsaacRng
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pub fn new_unseeded() -> Self
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use the FromEntropy or SeedableRng trait
Create an ISAAC random number generator using the default fixed seed.
DEPRECATED. IsaacRng::new_from_u64(0)
will produce identical results.
pub fn new_from_u64(seed: u64) -> Self
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use SeedableRng::seed_from_u64 instead
Create an ISAAC 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 IsaacRng
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fn clone(&self) -> IsaacRng
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fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl Debug for IsaacRng
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impl RngCore for IsaacRng
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fn next_u32(&mut self) -> u32
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fn next_u64(&mut self) -> u64
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fn fill_bytes(&mut self, dest: &mut [u8])
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fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>
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impl SeedableRng for IsaacRng
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type Seed = <IsaacCore as SeedableRng>::Seed
Seed type, which is restricted to types mutably-dereferencable as u8
arrays (we recommend [u8; N]
for some N
). Read more
fn from_seed(seed: Self::Seed) -> Self
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fn seed_from_u64(seed: u64) -> Self
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Create an ISAAC 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.
fn from_rng<S: RngCore>(rng: S) -> Result<Self, Error>
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Auto Trait Implementations
Blanket Implementations
impl<R> Rng for R where
R: RngCore + ?Sized,
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R: RngCore + ?Sized,
fn gen<T>(&mut self) -> T where
Standard: Distribution<T>,
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Standard: Distribution<T>,
Return a random value supporting the [Standard
] distribution. Read more
fn gen_range<T: PartialOrd + SampleUniform>(&mut self, low: T, high: T) -> T
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Generate a random value in the range [low
, high
), i.e. inclusive of low
and exclusive of high
. Read more
fn sample<T, D: Distribution<T>>(&mut self, distr: D) -> T
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Sample a new value, using the given distribution. Read more
ⓘImportant traits for DistIter<'a, D, R, T>fn sample_iter<'a, T, D: Distribution<T>>(
&'a mut self,
distr: &'a D
) -> DistIter<'a, D, Self, T> where
Self: Sized,
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&'a mut self,
distr: &'a D
) -> DistIter<'a, D, Self, T> where
Self: Sized,
Create an iterator that generates values using the given distribution. Read more
fn fill<T: AsByteSliceMut + ?Sized>(&mut self, dest: &mut T)
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Fill dest
entirely with random bytes (uniform value distribution), where dest
is any type supporting [AsByteSliceMut
], namely slices and arrays over primitive integer types (i8
, i16
, u32
, etc.). Read more
fn try_fill<T: AsByteSliceMut + ?Sized>(
&mut self,
dest: &mut T
) -> Result<(), Error>
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&mut self,
dest: &mut T
) -> Result<(), Error>
Fill dest
entirely with random bytes (uniform value distribution), where dest
is any type supporting [AsByteSliceMut
], namely slices and arrays over primitive integer types (i8
, i16
, u32
, etc.). Read more
fn gen_bool(&mut self, p: f64) -> bool
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Return a bool with a probability p
of being true. Read more
fn choose<'a, T>(&mut self, values: &'a [T]) -> Option<&'a T>
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Return a random element from values
. Read more
fn choose_mut<'a, T>(&mut self, values: &'a mut [T]) -> Option<&'a mut T>
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Return a mutable pointer to a random element from values
. Read more
fn shuffle<T>(&mut self, values: &mut [T])
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Shuffle a mutable slice in place. Read more
ⓘImportant traits for Generator<T, R>fn gen_iter<T>(&mut self) -> Generator<T, &mut Self> where
Standard: Distribution<T>,
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Standard: Distribution<T>,
use Rng::sample_iter(&Standard) instead
Return an iterator that will yield an infinite number of randomly generated items. Read more
fn gen_weighted_bool(&mut self, n: u32) -> bool
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use gen_bool instead
Return a bool with a 1 in n chance of true Read more
ⓘImportant traits for AsciiGenerator<R>fn gen_ascii_chars(&mut self) -> AsciiGenerator<&mut Self>
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use sample_iter(&Alphanumeric) instead
Return an iterator of random characters from the set A-Z,a-z,0-9. Read more
impl<R> FromEntropy for R where
R: SeedableRng,
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R: SeedableRng,
fn from_entropy() -> R
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impl<T> From for T
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impl<T, U> Into for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T, U> TryFrom for T where
T: From<U>,
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T: From<U>,
type Error = !
try_from
)The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T> Borrow for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T, U> TryInto for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
try_from
)The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,