nut_sys

nut_sys is a low-level Rust wrapper for the Number Theory Utils (nut) C library. It provides raw FFI bindings and some safe wrappers. Not all functions from the C library are currently exported, more will be added as needed.

Build Options

• Use Preinstalled Library: Link to an already installed version of the nut library.
• Automatically Build from Source: Download and compile the nut C library from a submodule (requires --features build-c).

Installation

Using an Installed nut Library

If you already have the nut library installed on your system, you might need to set the NUT_LIB_DIR environment variable if it is in a non-standard location. Then just run cargo build as normal:

export NUT_LIB_DIR=/path/to/nut/lib
cargo build

For example, the default install location is /usr/local/lib/, which is usually in the library path, but not for some linkers like mold.

Automatically Building nut from Source

If you do not have nut installed and do not want to manually build it:

1. Clone the repository and initialize the submodule:

   git submodule update --recursive --init
   

2. Build the Rust crate with the build-c feature enabled:

   cargo build --features build-c
   

This will compile the nut library and link it statically to your Rust crate.

You can also then install or run more tests on the copy of nut that cargo downloaded, but be careful because changing the <repository>/nut/ directory can cause build.rs to re-run.

Usage

Add nut_sys to your Cargo.toml:

[dependencies]
nut_sys = "0.1.0" # Replace with the latest version from crates.io

Then, in your Rust code:

use nut_sys::{sieve_largest_factors, Factors};

fn main() -> Result<(), ThinBox<dyn Error>> {
	let largest_factors = sieve_largest_factors(100_0000u64);
	let largest_factors: &[_] = largest_factors.borrow();
	let mut count = 0;
	let mut fxn = Factors::make_ub(100_000);
	for n in 1..=100_000 {
		fxn.fill_from_largest_factors(n, largest_factors);
		if (0..fxn.num_primes()).all(|i|fxn[i].power == 1) {
			count += 1;
		}
	}
	println!("Found {count} squarefree numbers up to 100_000");
	Ok(())
}

Links

• Crate: https://crates.io/crates/nut_sys
• C Library Repository: https://github.com/hacatu/Number-Theory-Utils
• Documentation: https://docs.rs/nut_sys

License

nut_sys and nut are both licensed under MPL-2.0. See LICENSE for details.