dby-node-ffi

node-ffi
========

$3


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.

Example
-------

`` js
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][tutorial].

Requirements
------------

* 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.

Installation
------------

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

` bash
$ npm install ffi
`

Source Install / Manual Compilation
-----------------------------------

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

` bash
$ npm install -g node-gyp
`

Now you can compile node-ffi:

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

Types
-----

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

V8 and 64-bit Types
-------------------

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.

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.

[v1apichanges]: https://github.com/node-ffi/node-ffi/wiki/API-changes-from-v0.x-to-v1.x
[tutorial]: https://github.com/node-ffi/node-ffi/wiki/Node-FFI-Tutorial
[ref-types]: https://github.com/TooTallNate/ref#built-in-types