Rust C-ABI Library Template

A minimal template for building a Rust library and calling it from C-ABI languages including C, JavaScript (Node.js), Lua, and Python.

The minimal library, src/lib.rs, includes a landing pad to catch panics in the Rust code and prevent them from cross the FFI boundary. The main function rust_function() expects to receive a C string as an argument, and returns a pointer to a C-formatted struct containing a result code and a pointer to a C string message or payload:

#[repr(C)]
pub struct CallResult {
   status: i32,
   text: *mut c_char
}

The landing pad in rust_function() will use this struct to return whatever its protected code returns, unless a panic occurs. When a panic is caught, it returns a status of 2 and a text message describing the panic.

Since the CallResult struct is allocated by Rust, it must be freed by Rust, so the calling application must call free_result() to release the memory.

Travis Continuous Integration

Also included is a Travis-CI configuration for building a Rust library as part of a project written in another language (in this case, Python). At present, the Travis Rust documentation describes how to use their service for projects that are primarily Rust-based ('language: rust'), but not how to add Rust components to an existing (e.g. 'language: python') project.

C

No makefile is included for the c_test.c test application, but it can be built and run somewhat like this:

$ cargo build
$ gcc -Wall -O2 -o c_test c_test.c -L target/debug -lrust_c_abi_library_template
$ LD_LIBRARY_PATH=target/debug ./c_test

Lua

The lua_test.lua test application was tested using Lua 5.3 with Pierre Chapuis's fork of luaffi, which adds Lua 5.3 to James McKaskill's (unmaintained?) version. Either McKaskill's version or the FaceBook fork will probably work with older versions of Lua.

Example:

$ # install luaffi using your favorite method
$ cargo build
$ lua lua_test.lua

Node.js

The node_test.js test application was tested using Node 6.9.1 and the ffi, ref, and ref-struct packages.

Example:

$ cargo build
$ npm install
$ node node_test.js

Python

The python_test.py test application will run under Python 2 or 3, using the standard library ctypes module.

Example:

$ cargo build
$ python python_test.py

License

rust_c-abi_library_template is copyright © 2017 Sean Bolton, and licensed under the MIT license:

Copyright (c) 2017 Sean Bolton

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.