Generate random numbers using only standard library

Overview

This Rust crate provides various random number generation utilities, including:

• Random u8,u16,u32,u64,u128,usize generation.
• Non negative i8,i16,i32,i64,i128,isize generation
• Floating-point randomness (f32 and f64) in [0,1).
• Random byte filling for buffers.
• Random range filling for slices.
• Random number generation from Range.
• High entropy random number generation by using separate thread RandomState.
• Fast but lower-entropy alternatives using thread local RandomState.

Features

• Minimal supported Rust version 1.56. Entire 2021 Rust edition is supported.
• No external dependencies beyond standard Rust library.
• Thread-based randomness: Uses separate threads for improved entropy (random_u64()).
• Secure and fast implementations for generating random numbers.
• Uniform distribution ensured for floating-point values.

Functions returning random numbers

random_u128(), random_u64(), random_u32(), random_u16(), random_u8(), random_usize()

Generates a unsigned high entropy random number in a separate thread. These numbers are unpredictable - true randoms. Numbers have uniform distribution and pass chi square test with very good score. While they are not certified for cryptographic purposes, they are good source of randomness for seeding other random generators.

fast_u128(), fast_u64(), fast_u32(), fast_u16(), fast_u8(), fast_usize()

Generates a lower entropy random number from the current thread. This randomness is much faster and it still maintains a uniform distribution. First number generated in the thread is fully random. Internally, it uses SipHash13 with 2x64-bit internal state, which is incremented by one on each call, resulting in progressively lower randomness.

As expected, the chi square test score is several times worse than in the random_ family. While the chi square test is worse, it is still within the widely accepted limits for fast random number generators.

These random numbers are definitely not suitable for generating cryptographic keys or for applications where hash resistance is required.

random_f64(), random_f32()

Generates a high entropy random floating point number in a separate thread from in [0, 1) range. These numbers have uniform distribution and pass chi square test.

fast_f32(), fast_f64()

Generates a lower entropy random floating point number in [0, 1).

Helper Functions

fill_bytes(), fill_numbers()

Fills slice with random numbers with provided generator.

gen_range(), fill_range()

Generate random number from specified range.

No copyright

This is free and unencumbered software released into the public domain.

You may use, modify, distribute, and contribute to this code without restriction. To the extent possible under law, the author(s) of this work waive all copyright and related rights.

Licensed under CC0-1.0 OR Unlicense.