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

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

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

This struct is available as rand_core::SysRng and as rand::rngs::SysRng. In both cases, this requires the crate feature sys_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 SysRng will block until the system's RNG is initialised. It is also possible (though highly unlikely) for SysRng 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::{SmallRng, SysRng};

let rng = SmallRng::try_from_rng(SysRng)?;
let v = rng.random::<u64>();