Struct OsRng

pub struct OsRng;

An interface over the operating-system’s random data source

This is a zero-sized struct. It can be freely constructed with just OsRng.

The implementation is provided by the getrandom crate. Refer to getrandom documentation for details.

This struct is available as rand_core::OsRng and as rand::rngs::OsRng. In both cases, this requires the crate feature os_rng or std (enabled by default in rand but not in rand_core).

Blocking and error handling

It is possible that when used during early boot the first call to OsRng will block until the system’s RNG is initialised. It is also possible (though highly unlikely) for OsRng to fail on some platforms, most likely due to system mis-configuration.

After the first successful call, it is highly unlikely that failures or significant delays will occur (although performance should be expected to be much slower than a user-space PRNG).

Usage example

use rand_core::{TryRngCore, OsRng};

let mut key = [0u8; 16];
OsRng.try_fill_bytes(&mut key).unwrap();
let random_u64 = OsRng.try_next_u64().unwrap();

Trait Implementations

impl Clone for OsRng

fn clone(&self) -> OsRng

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for OsRng

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

Formats the value using the given formatter.

impl Default for OsRng

fn default() -> OsRng

Returns the “default value” for a type.

impl TryRngCore for OsRng

type Error = OsError

The type returned in the event of a RNG error.

fn try_next_u32(&mut self) -> Result<u32, Self::Error>

Return the next random u32.

fn try_next_u64(&mut self) -> Result<u64, Self::Error>

Return the next random u64.

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

Fill dest entirely with random data.

fn unwrap_err(self) -> UnwrapErr<Self>

where Self: Sized,

Wrap RNG with the UnwrapErr wrapper.

fn read_adapter(&mut self) -> RngReadAdapter<'_, Self>

where Self: Sized,

Convert an RngCore to a RngReadAdapter.

impl Copy for OsRng

impl TryCryptoRng for OsRng