node-ffi is a Node.js 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 node.js 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: node-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.

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

For a more detailed introduction, see the node-ffi tutorial page.

• Linux, OS X, Windows, or Solaris.
• libffi comes bundled with node-ffi; it does not need to be installed on your system.
• The current version is tested to run on node v0.6, v0.8, v0.9 and v0.10.

Make sure you"ve installed all the necessary build tools for your platform, then invoke:

$ npm install ffi

To compile from source it"s easiest to use node-gyp:

$ npm install -g node-gyp

Now you can compile node-ffi:

$ git clone git://github.com/node-ffi/node-ffi.git
$ cd node-ffi
$ node-gyp rebuild

The types that you specify in function declarations correspond to ref"s types system. So see its docs for a reference if you are unfamiliar.

Internally, V8 stores integers that will fit into a 32-bit space in a 32-bit integer, and those that fall outside of this get put into double-precision floating point (FP) numbers. This is problematic because FP numbers are imprecise. To get around this, the methods in node-ffi that deal with 64-bit integers return strings and can accept strings as parameters.

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.

MIT License. See the LICENSE file.