A tiny, fast, zero-dep library for random number generation.

no-std, entropy, rand, random


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Current version: 0.4.0

A library meant for fast, random number generation with quick compile time, and minimal dependencies.


Generating a number

use nanorand::{RNG, WyRand};

fn main() {
    let mut rng = WyRand::new();
    println!("Random number: {}", rng.generate::<u64>());

Generating a number in a range

use nanorand::{RNG, WyRand};

fn main() {
    let mut rng = WyRand::new();
    println!("Random number between 1 and 100: {}", rng.generate_range::<u64>(1, 100));

Shuffling a Vec

use nanorand::{RNG, WyRand};

fn main() {
    let mut rng = WyRand::new();
    let mut items = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
    rng.shuffle(&mut items);

Why should I use this over...

  • rand - The standard rand crate is a complex beast. It contains unsafe code in the core implementations, and while it has much more options than we do, that's kind of the point. We're straight to the point, while rand is everything and the kitchen sink.
  • fastrand, oorandom, random-fast-rng, or randomize - These are all minimal, zero-dep implementations of the PCG family of RNGs (Pcg32 and Pcg64). While these are decent, they are much slower than wyrand (which beats the speed of these Pcg32 implementations while providing 64 random bits), and do not provide CSPRNGs.
  • getrandom - The getrandom crate just provides OS entropy sources. It is not meant for random number generation. In fact, it is useful for seeding nanorand's RNGs on platforms where we can't do that ourselves.

RNG Implementations

RNG nanorand type Output Size Cryptographically Secure Speed Notes Original Implementation
wyrand nanohash::WyRand 64 bits (u64) 🚫 4 GB/s
Pcg64 nanohash::Pcg64 64 bits (u64) 🚫 1 GB/s
ChaCha nanohash::ChaCha 512 bits ([u32; 16]) 90 MB/s (ChaCha8), 40 MB/s (ChaCha20) Currently only works in Nightly Rust, will work with Stable 1.47 (see rust#74060)

Entropy Sources

  • Unix-like (Linux, Android, macOS, iOS, FreeBSD, OpenBSD) - first /dev/urandom, else /dev/random, else system time. (#[forbid(unsafe_code)])
  • Windows - BCryptGenRandom with system-preferred RNG. (#[deny(unsafe_code)])

Feature Flags

  • std (default) - Enables Rust std lib features, such as seeding from OS entropy sources.
  • wyrand (default) - Enable the wyrand RNG.
  • pcg64 (default) - Enable the Pcg64 RNG.
  • chacha (Nightly-only) - Enable the ChaCha RNG.
  • rdseed - On x86/x86_64 platforms, the rdseed intrinsic will be used when OS entropy isn't available.
  • zeroize - Implement the Zeroize trait for all RNGs.


The zlib/libpng License

Copyright (c) 2020 aspen

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.

  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.

  3. This notice may not be removed or altered from any source distribution.