Struct rand::rngs::StdRng

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pub struct StdRng(/* private fields */);
Expand description

A strong, fast (amortized), non-portable RNG

This is the “standard” RNG, a generator with the following properties:

  • Non-portable: any future library version may replace the algorithm and results may be platform-dependent. (For a portable version, use the rand_chacha crate directly.)
  • CSPRNG: statistically good quality of randomness and unpredictable
  • Fast (amortized): the RNG is fast for bulk generation, but the cost of method calls is not consistent due to usage of an output buffer.

The current algorithm used is the ChaCha block cipher with 12 rounds. Please see this relevant rand issue for the discussion. This may change as new evidence of cipher security and performance becomes available.

§Seeding (construction)

This generator implements the SeedableRng trait. Any method may be used, but note that seed_from_u64 is not suitable for usage where security is important. Also note that, even with a fixed seed, output is not portable.

It is suggested to use a fresh seed direct from the OS as the most secure and convenient option:

let rng = StdRng::from_os_rng();

See also Seeding RNGs in the book.

§Generation

The generators implements RngCore and thus also Rng. See also the Random Values chapter in the book.

Trait Implementations§

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impl Clone for StdRng

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fn clone(&self) -> StdRng

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for StdRng

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

Formats the value using the given formatter. Read more
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impl PartialEq for StdRng

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fn eq(&self, other: &StdRng) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl RngCore for StdRng

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fn next_u32(&mut self) -> u32

Return the next random u32. Read more
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fn next_u64(&mut self) -> u64

Return the next random u64. Read more
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fn fill_bytes(&mut self, dst: &mut [u8])

Fill dest with random data. Read more
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impl SeedableRng for StdRng

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type Seed = [u8; 32]

Seed type, which is restricted to types mutably-dereferenceable as u8 arrays (we recommend [u8; N] for some N). Read more
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fn from_seed(seed: Self::Seed) -> Self

Create a new PRNG using the given seed. Read more
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fn seed_from_u64(state: u64) -> Self

Create a new PRNG using a u64 seed. Read more
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fn from_rng(rng: impl RngCore) -> Self

Create a new PRNG seeded from an infallible Rng. Read more
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fn try_from_rng<R>(rng: R) -> Result<Self, <R as TryRngCore>::Error>
where R: TryRngCore,

Create a new PRNG seeded from a potentially fallible Rng. Read more
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fn from_os_rng() -> Self

Creates a new instance of the RNG seeded via getrandom. Read more
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fn try_from_os_rng() -> Result<Self, Error>

Creates a new instance of the RNG seeded via getrandom without unwrapping potential getrandom errors. Read more
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impl TryRngCore for StdRng

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type Error = Infallible

The type returned in the event of a RNG error.
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fn try_next_u32(&mut self) -> Result<u32, Self::Error>

Return the next random u32.
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fn try_next_u64(&mut self) -> Result<u64, Self::Error>

Return the next random u64.
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fn try_fill_bytes(&mut self, dst: &mut [u8]) -> Result<(), Self::Error>

Fill dest entirely with random data.
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fn unwrap_err(self) -> UnwrapErr<Self>
where Self: Sized,

Wrap RNG with the UnwrapErr wrapper.
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fn read_adapter(&mut self) -> RngReadAdapter<'_, Self>
where Self: Sized,

Convert an RngCore to a RngReadAdapter.
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impl CryptoRng for StdRng

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impl Eq for StdRng

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impl StructuralPartialEq for StdRng

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impl TryCryptoRng for StdRng

Auto Trait Implementations§

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impl Freeze for StdRng

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impl RefUnwindSafe for StdRng

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impl Send for StdRng

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impl Sync for StdRng

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impl Unpin for StdRng

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impl UnwindSafe for StdRng

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<R> Rng for R
where R: RngCore + ?Sized,

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fn random<T>(&mut self) -> T

Return a random value via the Standard distribution. Read more
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fn gen_range<T, R>(&mut self, range: R) -> T
where T: SampleUniform, R: SampleRange<T>,

Generate a random value in the given range. Read more
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fn gen_iter<T>(self) -> DistIter<Standard, Self, T>
where Self: Sized, Standard: Distribution<T>,

Generate values via an iterator Read more
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fn sample<T, D: Distribution<T>>(&mut self, distr: D) -> T

Sample a new value, using the given distribution. Read more
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fn sample_iter<T, D>(self, distr: D) -> DistIter<D, Self, T>
where D: Distribution<T>, Self: Sized,

Create an iterator that generates values using the given distribution. Read more
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fn fill<T: Fill + ?Sized>(&mut self, dest: &mut T)

Fill any type implementing Fill with random data Read more
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fn gen_bool(&mut self, p: f64) -> bool

Return a bool with a probability p of being true. Read more
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fn gen_ratio(&mut self, numerator: u32, denominator: u32) -> bool

Return a bool with a probability of numerator/denominator of being true. I.e. gen_ratio(2, 3) has chance of 2 in 3, or about 67%, of returning true. If numerator == denominator, then the returned value is guaranteed to be true. If numerator == 0, then the returned value is guaranteed to be false. Read more
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fn gen<T>(&mut self) -> T

👎Deprecated since 0.9.0: Renamed to random to avoid conflict with the new gen keyword in Rust 2024.
Alias for Rng::random.
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V