Package Exports
- ffi-napi
- ffi-napi/lib/bindings.js
This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (ffi-napi) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.
Readme
node-ffi-napi
Node.js Foreign Function Interface for N-API
node-ffi-napi
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-napi
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.
WARNING: The original API of node-ffi
is left mostly untouched in the
N-API wrapper. However, the API did not have very well-defined properties
in the context of garbage collection and multi-threaded execution. It is
recommended to avoid any multi-threading usage of this library
if possible.
Example
var ffi = require('ffi-napi');
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.
Requirements
- Linux, OS X, Windows, or Solaris.
libffi
comes bundled with node-ffi-napi; it does not need to be installed on your system.- The current version is tested to run on Node 6 and above.
Installation
Make sure you've installed all the necessary build tools for your platform, then invoke:
$ npm install ffi-napi
Source Install / Manual Compilation
To compile from source it's easiest to use
node-gyp
:
$ npm install -g node-gyp
Now you can compile node-ffi-napi
:
$ git clone git://github.com/node-ffi-napi/node-ffi-napi.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 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 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.