test.h

struct simpleStruct {
  int a;
  char* b;
};

typedef struct simpleStruct s1;

struct myStruct {
  int a;
  char* b;
  union {
    int foo;
    double bar;
  };
};

typedef struct myStruct s2;

void foofunc(s2);

void unfunc(s1);

test.js

var FFI = require('ffi'),
    ArrayType = require('ref-array'),
    Struct = require('ref-struct'),
    ref = require('ref');

var voidPtr = ref.refType(ref.types.void);

exports.CONSTANTS = {
};

var myStruct = exports.myStruct = Struct({
  a: ref.types.int32,
  b: ref.types.CString,
  union0: Union({
  foo: ref.types.int32,
  bar: ref.types.double,
}),
});
var myStructPtr = exports.myStructPtr = ref.refType(myStruct);
var simpleStruct = exports.simpleStruct = Struct({
  a: ref.types.int32,
  b: ref.types.CString,
});
var simpleStructPtr = exports.simpleStructPtr = ref.refType(simpleStruct);

exports.test = new FFI.Library('test', {
  foofunc: [ref.types.void, [
    myStruct,
  ]],
  unfunc: [ref.types.void, [
    simpleStruct,
  ]],
});