README.md

Libusb Rust Bindings

The libusb1-sys crate provides declarations and linkage for the libusb C library. Following the *-sys package conventions, the libusb1-sys crate does not define higher-level abstractions over the native libusb library functions.

Dependencies

In order to use the libusb1-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 libusb1-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 libusb1-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 libusb1-sys as a dependency in Cargo.toml:

[dependencies]
libusb1-sys = "0.6"

Import the libusb1_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 libusb1_sys as ffi;

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

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

Native dependencies

libusb1-sys exports metadata so that dependent crates can find the correct libusb.h header and compile native code that depends on libusb. If a crate has a direct dependency on libusb1-sys, its build script has access to the following environment variables:

• DEP_USB_1.0_INCLUDE contains the include path with the correct libusb.h
• DEP_USB_1.0_VENDORED is set with a value of 1 if libusb1-sys compiled and linked to its vendored copy of libusb
• DEP_USB_1.0_STATIC is set with a value of 1 if static linkage has been used instead of dynamic.

Finding Help

Since libusb1-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

Distributed under the MIT License.

License note.

If you link native libusb library statically then you must follow GNU LGPL from libusb.