napi: Implement napi_instanceof()

Since FunctionTemplate::HasInstance() is inaccessible, we must implement
the Javascript instanceof operator using the public V8 API. This does
that, and uses the V8 tests for instanceof to ensure that the semantics
of the API are identical to the semantics of the Javascript operator.

Closes nodejs#48

src/node_jsvmapi.cc

@@ -815,6 +815,47 @@ napi_value napi_new_instance(napi_env e, napi_value cons,
   return v8impl::JsValueFromV8LocalValue(result);
 }
 
+bool napi_instanceof(napi_env e, napi_value obj, napi_value cons) {
+  bool returnValue = false;
+
+  v8::Local<v8::Value> v8Obj = v8impl::V8LocalValueFromJsValue(obj);
+  v8::Local<v8::Value> v8Cons = v8impl::V8LocalValueFromJsValue(cons);
+  v8::Isolate *isolate = v8impl::V8IsolateFromJsEnv(e);
+
+  if (!v8Cons->IsFunction()) {
+    napi_throw_type_error(e, "constructor must be a function");
+
+    // Error handling needs to be done here
+    return false;
+  }
+
+  v8Cons =
+    v8Cons->ToObject()->Get(v8::String::NewFromUtf8(isolate, "prototype"));
+
+  if (!v8Cons->IsObject()) {
+    napi_throw_type_error(e, "constructor prototype must be an object");
+
+    // Error handling needs to be done here
+    return false;
+  }
+
+  if (!v8Obj->StrictEquals(v8Cons)) {
+    for (v8::Local<v8::Value> originalObj = v8Obj;
+        !(v8Obj->IsNull() || v8Obj->IsUndefined());
+        v8Obj = v8Obj->ToObject()->GetPrototype()) {
+      if (v8Obj->StrictEquals(v8Cons)) {
+        returnValue =
+          !(originalObj->IsNumber() ||
+            originalObj->IsBoolean() ||
+            originalObj->IsString());
+        break;
+      }
+    }
+  }
+
+  return returnValue;
+}
+
 napi_value napi_make_external(napi_env e, napi_value v) {
     return v;
 }

src/node_jsvmapi.h

@@ -206,6 +206,7 @@ NODE_EXTERN napi_value napi_call_function(napi_env e, napi_value scope,
                                           int argc, napi_value* argv);
 NODE_EXTERN napi_value napi_new_instance(napi_env e, napi_value cons,
                                          int argc, napi_value* argv);
+NODE_EXTERN bool napi_instanceof(napi_env e, napi_value obj, napi_value cons);
 
 // Temporary method needed to support wrapping JavascriptObject in an external 
 // object wrapper capable of storing external data. This workaround is only 

test/addons-abi/test_instanceof/binding.gyp

@@ -0,0 +1,8 @@
+{
+  "targets": [
+    {
+      "target_name": "test_instanceof",
+      "sources": [ "test_instanceof.cc" ]
+    }
+  ]
+}

test/addons-abi/test_instanceof/test.js

@@ -0,0 +1,37 @@
+var fs = require( 'fs' );
+
+require('../../common');
+var assert = require('assert');
+var addon = require('./build/Release/test_instanceof');
+var path = require( 'path' );
+
+function assertTrue(assertion) {
+  return assert.strictEqual(true, assertion);
+}
+
+function assertFalse(assertion) {
+  assert.strictEqual(false, assertion);
+}
+
+function assertEquals(leftHandSide, rightHandSide) {
+  assert.equal(leftHandSide, rightHandSide);
+}
+
+function assertThrows(statement) {
+  assert.throws(function() {
+    eval(statement);
+  }, Error);
+}
+
+function testFile( fileName ) {
+  eval( fs.readFileSync( fileName, { encoding: 'utf8' } )
+    .replace( /[(]([^\s(]+)\s+instanceof\s+([^)]+)[)]/g,
+      '( addon.doInstanceOf( $1, $2 ) )' ) );
+}
+
+testFile(
+  path.join( path.resolve( __dirname, '..', '..', '..', 'deps', 'v8', 'test', 'mjsunit' ),
+    'instanceof.js' ) );
+testFile(
+  path.join( path.resolve( __dirname, '..', '..', '..', 'deps', 'v8', 'test', 'mjsunit' ),
+    'instanceof-2.js' ) );

test/addons-abi/test_instanceof/test_instanceof.cc

@@ -0,0 +1,19 @@
+#include <node_jsvmapi.h>
+#include <stdio.h>
+
+void doInstanceOf(napi_env env, napi_func_cb_info info) {
+  napi_value arguments[2];
+
+  napi_get_cb_args(env, info, arguments, 2);
+
+  napi_set_return_value(env, info,
+    napi_create_boolean(env, napi_instanceof(env, arguments[0], arguments[1])));
+}
+
+void Init(napi_env env, napi_value exports, napi_value module) {
+  napi_set_property(env, exports,
+                    napi_property_name(env, "doInstanceOf"),
+                    napi_create_function(env, doInstanceOf));
+}
+
+NODE_MODULE_ABI(addon, Init)