roblabla / libusb-sys

Rust bindings for the libusb library.

Libusb Rust Bindings

The libusb-sys crate provides declarations and linkage for the libusb C library. Following the *-sys package conventions, the libusb-sys crate does not define higher-level abstractions over the native libusb library functions.

Dependencies

In order to use the libusb-sys crate, you must have the libusb library installed where it can be found by pkg-config.

All systems supported by libusb are also supported by the libusb-sys crate. It's been tested on Linux, OS X, and Windows.

Cross-Compiling

To link to a cross-compiled version of the native libusb library, it's necessary to set several environment variables to configure pkg-config to work with a cross-compiler's sysroot. Autotools Mythbuster has a good explanation of supporting cross-compilation with pkg-config.

However, Rust's pkg-config build helper doesn't support calling a $CHOST-prefixed pkg-config. It will always call pkg-config without a prefix. To cross-compile libusb-sys with the pkg-config build helper, one must define the environment variables PKG_CONFIG_DIR, PKG_CONFIG_LIBDIR, and PKG_CONFIG_SYSROOT_DIR for the default pkg-config. It's also necessary to set PKG_CONFIG_ALLOW_CROSS to tell Rust's pkg-config helper that it's okay to proceed with a cross-compile.

To adapt the pkg-config wrapper in the Autotools Mythbuster guide so that it works with Rust, one will end up with a script similar to the following:

#!/bin/sh

SYSROOT=/build/root

export PKG_CONFIG_DIR=
export PKG_CONFIG_LIBDIR=${SYSROOT}/usr/lib/pkgconfig:${SYSROOT}/usr/share/pkgconfig
export PKG_CONFIG_SYSROOT_DIR=${SYSROOT}
export PKG_CONFIG_ALLOW_CROSS=1

cargo build

Usage

Add libusb-sys as a dependency in Cargo.toml:

[dependencies]
libusb-sys = "0.2"

Import the libusb_sys crate and use the functions as they're defined in the native libusb library. See the libusb 1.0 API documention for more usage information.

extern crate libusb_sys as ffi;

fn main() {
  let version = unsafe { ffi::libusb_get_version() };

  println!("libusb v{}.{}.{}.{}", version.major, version.minor, version.micro, version.nano);
}

Finding Help

Since libusb-sys is no more than a wrapper around the native libusb library, the best source for help is the information already available for libusb:

• Home Page
• API Documentation
• Source

License

Copyright © 2015 David Cuddeback

Distributed under the MIT License.