This gist has been moved to `ref-wchar` module on npm, see: https://github.com/TooTallNate/ref-wchar

test.js

var ffi = require('ffi')
var ref = require('ref')
var assert = require('assert')
var wchar_t = require('./wchar_t')

// now we can create our FFI'd "wcslen()" function
var libc = ffi.Library('libc', {
  wcslen: [ 'size_t', [ wchar_t ] ],
  wcstod: [ 'double', [ wchar_t, ref.refType(wchar_t) ] ]
})

// you pass regular JavaScript Strings to the FFI'd function and the "wchar_t"
// type we defined handles converting it to a proper Buffer behind the scenes.
assert.equal(5, libc.wcslen('hello'))
assert.equal(11, libc.wcslen('hello world'))
assert.equal(-3.14, libc.wcstod('-3.14', null))

wchar_t.js

/**
 * Module dependencies.
 */

var ref = require('ref')
var Iconv = require('iconv').Iconv

// vars used by the "wchar_t" type
var wchar_size, getter, setter

// On Windows they're UTF-16 (2-bytes), but on Unix platform they're UTF-32
// (4-bytes).
if ('win32' == process.platform) {
  wchar_size = 2
  getter = new Iconv('UTF-16' + ref.endianness, 'UTF-8')
  setter = new Iconv('UTF-8', 'UTF-16' + ref.endianness)
} else {
  wchar_size = 4
  getter = new Iconv('UTF-32' + ref.endianness, 'UTF-8')
  setter = new Iconv('UTF-8', 'UTF-32' + ref.endianness)
}

// Create a "wchar_t *" type. We use the "CString" type as a base since it's pretty
// close to what we actually want. We just have to define custom "get" and "set"
// functions and then we can use this type in FFI functions.
var wchar_t = Object.create(ref.types.CString)
wchar_t.get = function get (buf, offset) {
  var _buf = buf.readPointer(offset)
  if (_buf.isNull()) {
    return null
  }
  var stringBuf = _buf.reinterpretUntilZeros(wchar_size)
  return getter.convert(stringBuf).toString('utf8')
};
wchar_t.set = function set (buf, offset, val) {
  var _buf = val // val is a Buffer? it better be \0 terminated...
  if ('string' == typeof val) {
    _buf = setter.convert(val + '\0')
  }
  return buf.writePointer(_buf, offset)
};

this gist has been moved to ref-wchar module on npm

See: https://github.com/TooTallNate/ref-wchar