dlopen2

This is a fork of the original, now unmaintained dlopen with updated dependencies, bug fixes and some new features.

Overview

This library is my effort to make use of dynamic link libraries in Rust simple. Previously existing solutions were either unsafe, provided huge overhead of required writing too much code to achieve simple things. I hope that this library will help you to quickly get what you need and avoid errors.

Quick example

use dlopen2::wrapper::{Container, WrapperApi};

#[derive(WrapperApi)]
struct Api<'a> {
    example_rust_fun: fn(arg: i32) -> u32,
    example_c_fun: unsafe extern "C" fn(),
    example_reference: &'a mut i32,
    // A function or field may not always exist in the library.
    example_c_fun_option: Option<unsafe extern "C" fn()>,
    example_reference_option:  Option<&'a mut i32>,
}

fn main(){
    let mut cont: Container<Api> =
        unsafe { Container::load("libexample.so") }.expect("Could not open library or load symbols");
    cont.example_rust_fun(5);
    unsafe{ cont.example_c_fun() };
    *cont.example_reference_mut() = 5;
    
    // Optional functions return Some(result) if the function is present or None if absent.
    unsafe{ cont.example_c_fun_option() };
    // Optional fields are Some(value) if present and None if absent.
    if let Some(example_reference) = &mut cont.example_reference_option {
        *example_reference = 5;
    }
}

Features

Main features

Supports majority of platforms and is platform independent.
Is consistent with Rust error handling mechanism and makes making mistakes much more difficult.
Is very lightweight. It mostly uses zero cost wrappers to create safer abstractions over platform API.
Is thread safe.
Is object-oriented programming friendly.
Has a low-level API that provides full flexibility of using libraries.
Has two high-level APIs that protect against dangling symbols - each in its own way.
High level APIs support automatic loading of symbols into structures. You only need to define a structure that represents an API. The rest happens automatically and requires only minimal amount of code.
Automatic loading of symbols helps you to follow the DRY paradigm.

Comparison with other libraries

Feature	dlopen2	libloading	sharedlib
Basic functionality	Yes	Yes	Yes
Multiplatform	Yes	Yes	Yes
Dangling symbol prevention	Yes	Yes	Yes
Thread safety	Yes	Potential problem with thread-safety of `dlerror()` on some platforms like FreeBSD	No support for SetErrorMode (library may block the application on Windows)
Loading of symbols into structures	Yes	No	No
Overhead	Minimal	Minimal	Some overhead
Low-level, unsafe API	Yes	Yes	Yes
Object-oriented friendly	Yes	No	Yes
Load from the program itself	Yes	No	No
Obtaining address information (dladdr)	Yes	Unix only	No

Safety

Please note that while Rust aims at being 100% safe language, it does not yet provide mechanisms that would allow me to create a 100% safe library, so I had to settle on 99%. Also the nature of dynamic link libraries requires casting obtained pointers into types that are defined on the application side. And this cannot be safe. Having said that I still think that this library provides the best approach and greatest safety possible in Rust.

Usage

Cargo.toml:

[dependencies]
dlopen2 = "0.6"

Documentation

Cargo documentation

License

This code is licensed under the MIT license.

Changelog

GitHub changelog

Acknowledgement

Special thanks to Simonas Kazlauskas whose libloading became code base for my project.

dlopen2 0.6.1