Added promise support

lib/_foreign_function.js

@@ -6,6 +6,7 @@
 var assert = require('assert')
   , debug = require('debug')('ffi:_ForeignFunction')
   , ref = require('ref')
+  , Promise = require('any-promise')
   , bindings = require('./bindings')
   , POINTER_SIZE = ref.sizeof.pointer
   , FFI_ARG_SIZE = bindings.FFI_ARG_SIZE
@@ -117,6 +118,24 @@ function ForeignFunction (cif, funcPtr, returnType, argTypes) {
     })
   }
 
+  /**
+   * A promise based wrapper around .async
+   */
+
+  proxy.promise = function () {
+    var args = [].splice.call(arguments, 0)
+    return new Promise(function (resolve, reject) {
+      args.push(function (err, res) {
+        if (err) {
+          return reject(err)
+        } else {
+          return resolve(res)
+        }
+      })
+      proxy.async.apply(undefined, args)
+    })
+  }
+
   return proxy
 }
 module.exports = ForeignFunction

lib/library.js

@@ -60,13 +60,16 @@ function Library (libfile, funcs, lib) {
       , fopts = info[2]
       , abi = fopts && fopts.abi
       , async = fopts && fopts.async
+      , promise = fopts && fopts.promise
       , varargs = fopts && fopts.varargs
 
     if (varargs) {
       lib[func] = VariadicForeignFunction(fptr, resultType, paramTypes, abi)
     } else {
       var ff = ForeignFunction(fptr, resultType, paramTypes, abi)
-      lib[func] = async ? ff.async : ff
+      if (async) lib[func] = ff.async
+      else if (promise) lib[func] = ff.promise
+      else lib[func] = ff
     }
   })
 

package.json

@@ -23,11 +23,12 @@
   },
   "main": "./lib/ffi",
   "dependencies": {
+    "any-promise": "^1.1.0",
     "bindings": "~1.2.0",
     "debug": "2",
+    "nan": "2",
     "ref": "1",
-    "ref-struct": "1",
-    "nan": "2"
+    "ref-struct": "1"
   },
   "devDependencies": {
     "fs-extra": "^0.23.1",

test/foreign_function.js

@@ -201,4 +201,30 @@ describe('ForeignFunction', function () {
 
   })
 
+  describe('promise', function () {
+
+    it('should call the static "abs" bindings asynchronously', function () {
+      var _abs = bindings.abs
+      var abs = ffi.ForeignFunction(_abs, 'int', [ 'int' ])
+      assert.equal('function', typeof abs.async)
+
+      return abs.promise(-1234).then(function (res) {
+        assert.equal(res, 1234)
+      })
+    })
+
+    it('should invoke the callback with an Error with a meaningful message when type\'s `set()` throws', function () {
+      var _abs = bindings.abs
+      var abs = ffi.ForeignFunction(_abs, 'int', [ 'int' ])
+
+      return abs.promise(1111111111111111111111).catch(function (err) {
+        return err;
+      }).then(function (err) {
+        assert(err instanceof Error)
+        assert(/error setting argument 0/.test(err.message))
+      })
+    })
+
+  })
+
 })

test/library.js

@@ -149,4 +149,18 @@ describe('Library', function () {
 
   })
 
+  describe('promise', function () {
+
+    it('should call a function asynchronously and return a promise', function () {
+      var lib = process.platform == 'win32' ? 'msvcrt' : 'libm'
+      var libm = new Library(lib, {
+          'ceil': [ 'double', [ 'double' ], { promise: true } ]
+      })
+      return libm.ceil(1.1).then(function (res) {
+        assert.equal(res, 2)
+      })
+    })
+
+  })
+
 })