Struct `ThreadRng`

struct ThreadRng { ... }

A reference to the thread-local generator

This type is a reference to a lazily-initialized thread-local generator. An instance can be obtained via [rand::rng()][crate::rng()] or via [ThreadRng::default()]. The handle cannot be passed between threads (is not Send or Sync).

Security

Security must be considered relative to a threat model and validation requirements. The Rand project can provide no guarantee of fitness for purpose. The design criteria for ThreadRng are as follows:

Automatic seeding via OsRng and periodically thereafter (see (ReseedingRng documentation). Limitation: there is no automatic reseeding on process fork (see below).
A rigorusly analyzed, unpredictable (cryptographic) pseudo-random generator (see the book on security). The currently selected algorithm is ChaCha (12-rounds). See also StdRng documentation.
Not to leak internal state through Debug or serialization implementations.
No further protections exist to in-memory state. In particular, the implementation is not required to zero memory on exit (of the process or thread). (This may change in the future.)
Be fast enough for general-purpose usage. Note in particular that ThreadRng is designed to be a "fast, reasonably secure generator" (where "reasonably secure" implies the above criteria).

We leave it to the user to determine whether this generator meets their security requirements. For an alternative, see OsRng.

Fork

ThreadRng is not automatically reseeded on fork. It is recommended to explicitly call ThreadRng::reseed immediately after a fork, for example:

fn do_fork() {
    let pid = unsafe { libc::fork() };
    if pid == 0 {
        // Reseed ThreadRng in child processes:
        rand::rng().reseed();
    }
}

Methods on ThreadRng are not reentrant-safe and thus should not be called from an interrupt (e.g. a fork handler) unless it can be guaranteed that no other method on the same ThreadRng is currently executing.

Implementations

`impl ThreadRng`

fn reseed(self: &mut Self) -> Result<(), OsError>

Immediately reseed the generator

This discards any remaining random data in the cache.

`impl Clone for ThreadRng`

fn clone(self: &Self) -> ThreadRng

`impl CryptoRng for ThreadRng`

`impl Debug for ThreadRng`

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

`impl Default for ThreadRng`

fn default() -> ThreadRng

`impl Freeze for ThreadRng`

`impl RefUnwindSafe for ThreadRng`

`impl RngCore for ThreadRng`

fn next_u32(self: &mut Self) -> u32
fn next_u64(self: &mut Self) -> u64
fn fill_bytes(self: &mut Self, dest: &mut [u8])

`impl Send for ThreadRng`

`impl Sync for ThreadRng`

`impl Unpin for ThreadRng`

`impl UnsafeUnpin for ThreadRng`

`impl UnwindSafe for ThreadRng`

`impl<R> Rng for ThreadRng`

`impl<R> TryCryptoRng for ThreadRng`

`impl<R> TryRngCore for ThreadRng`

fn try_next_u32(self: &mut Self) -> Result<u32, <R as TryRngCore>::Error>
fn try_next_u64(self: &mut Self) -> Result<u64, <R as TryRngCore>::Error>
fn try_fill_bytes(self: &mut Self, dst: &mut [u8]) -> Result<(), <R as TryRngCore>::Error>

`impl<T> Any for ThreadRng`

fn type_id(self: &Self) -> TypeId

`impl<T> Borrow for ThreadRng`

fn borrow(self: &Self) -> &T

`impl<T> BorrowMut for ThreadRng`

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

`impl<T> CloneToUninit for ThreadRng`

unsafe fn clone_to_uninit(self: &Self, dest: *mut u8)

`impl<T> From for ThreadRng`

fn from(t: T) -> T: Returns the argument unchanged.

`impl<T> ToOwned for ThreadRng`

fn to_owned(self: &Self) -> T
fn clone_into(self: &Self, target: &mut T)

`impl<T, U> Into for ThreadRng`

fn into(self: Self) -> U

Calls U::from(self).

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

`impl<T, U> TryFrom for ThreadRng`

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

`impl<T, U> TryInto for ThreadRng`

fn try_into(self: Self) -> Result<U, <U as TryFrom<T>>::Error>

`impl<V, T> VZip for ThreadRng`

fn vzip(self: Self) -> V