shadow-ffi

ShadowNode Foreign Function Interface

shadow-ffi is a ShadowNode addon for loading and calling dynamic libraries using pure JavaScript. It can be used to create bindings to native libraries without writing any C++ code.

It also simplifies the augmentation of ShadowNode with C code as it takes care of handling the translation of types across JavaScript and C, which can add reams of boilerplate code to your otherwise simple C. See the example/factorial for an example of this use case.

WARNING: shadow-ffi assumes you know what you're doing. You can pretty easily create situations where you will segfault the interpreter and unless you've got C debugger skills, you probably won't know what's going on.

Example

var ffi = require('ffi');

var libm = ffi.Library('libm', {
  'ceil': [ 'double', [ 'double' ] ]
});
libm.ceil(1.5); // 2

// You can also access just functions in the current process by passing a null
var current = ffi.Library(null, {
  'atoi': [ 'int', [ 'string' ] ]
});
current.atoi('1234'); // 1234

Requirements

• Linux, OS X
• libffi comes bundled with shadow-ffi by default; it does not need to be installed on your system if you build shadow-ffi in static mode.

Installation

An easy way to install shadow-ffi is going to be implemented. Right now it has to be installed with source code documented as next section.

Source Install / Manual Compilation

$ git clone git://github.com/shadow-node/ffi.git shadow-ffi
$ cd shadow-ffi
$ npm run build

Use system libffi.{dylib,so}

shadow-ffi can be built with dynamically linked libffi. To build shadow-ffi dynamically linked:

$ npm run build -- --libffi-link-external

Call Overhead

There is non-trivial overhead associated with FFI calls. Comparing a hard-coded binding version of strtoul() to an FFI version of strtoul() shows that the native hard-coded binding is orders of magnitude faster. So don't just use the C version of a function just because it's faster. There's a significant cost in FFI calls, so make them worth it.

License

MIT License. See the LICENSE file.

A project derived from node-ffi.