commit	c9ae6ca7b5ba806832ec42cb530adbe6d22a3af2	[log] [tgz]
author	James Farrell <jamesfarrell@google.com>	Thu Sep 07 07:30:56 2023 +0000
committer	Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>	Thu Sep 07 07:30:56 2023 +0000
tree	f4ec7bf8a872174e4452a977a49e34bf2a1a6e87
parent	35a6cd73e97c97e5b9a6c8849b2b84c9dd1ec6ca [diff]
parent	13a4c085518fd96f61eec13e276687e69a722923 [diff]

tree: f4ec7bf8a872174e4452a977a49e34bf2a1a6e87

README.md

fastrand

A simple and fast random number generator.

The implementation uses Wyrand, a simple and fast generator but not cryptographically secure.

Examples

Flip a coin:

if fastrand::bool() {
    println!("heads");
} else {
    println!("tails");
}

Generate a random i32:

let num = fastrand::i32(..);

Choose a random element in an array:

let v = vec![1, 2, 3, 4, 5];
let i = fastrand::usize(..v.len());
let elem = v[i];

Sample values from an array with O(n) complexity (n is the length of array):

fastrand::choose_multiple(vec![1, 4, 5].iter(), 2);
fastrand::choose_multiple(0..20, 12);

Shuffle an array:

let mut v = vec![1, 2, 3, 4, 5];
fastrand::shuffle(&mut v);

Generate a random Vec or String:

use std::iter::repeat_with;

let v: Vec<i32> = repeat_with(|| fastrand::i32(..)).take(10).collect();
let s: String = repeat_with(fastrand::alphanumeric).take(10).collect();

To get reproducible results on every run, initialize the generator with a seed:

// Pick an arbitrary number as seed.
fastrand::seed(7);

// Now this prints the same number on every run:
println!("{}", fastrand::u32(..));

To be more efficient, create a new Rng instance instead of using the thread-local generator:

use std::iter::repeat_with;

let rng = fastrand::Rng::new();
let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();

Features

std (enabled by default): Enables the std library. This is required for the global generator and global entropy. Without this feature, [Rng] can only be instantiated using the with_seed method.

License

Licensed under either of

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.