WIP: Create a public v8::DictionarySchema API for bulk reads from dict objects.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 031ad5a0237ac420731bd4076a74d015666036be..f59333f017cddfb497db73cfc82638541b61d58f 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -1371,6 +1371,74 @@ Local<AccessorSignature> AccessorSignature::New(
   return Utils::AccessorSignatureToLocal(Utils::OpenHandle(*receiver));
 }
 
+Local<DictionarySchema> DictionarySchema::New(Isolate* v8_isolate,
+                                              Local<Value> keys[],
+                                              int keyCount) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
+  LOG_API(isolate, DictionarySchema, New);
+  ENTER_V8_NO_SCRIPT_NO_EXCEPTION(isolate);
+  i::Handle<i::DictionarySchema> schema =
+      i::DictionarySchema::New(isolate, keyCount);
+  for (int i = 0; i < keyCount; i++) {
+    i::Handle<i::Object> key = Utils::OpenHandle(*keys[i]);
+    uint32_t array_index;
+    Utils::ApiCheck(key->IsName() || key->ToArrayIndex(&array_index),
+                    "v8::DictionarySchema::New",
+                    "invalid dictionary key (must be name or array index)");
+    schema->set(i, *key);
+  }
+  return Utils::ToLocal(schema);
+}
+
+Maybe<bool> DictionarySchema::Get(Local<Context> context, Local<Object> object,
+                                  ValueFilter continue_filter,
+                                  Local<Value>* out, int out_length,
+                                  int* index) {
+  // TODO(jbroman): This is an ugly hack.
+  // We could return some V8 object (v8::Array? Something else?) that must be
+  // queried. Or we could at least wrap this up in something that doesn't
+  // require us to be a friend of v8::Local.
+  // It's also potentially quadratic at present, if everything fails the
+  // continue filter.
+  {
+    i::Isolate* isolate = reinterpret_cast<i::Isolate*>(context->GetIsolate());
+    for (int i = *index; i < out_length; i++) {
+      out[i] =
+          Local<Value>(reinterpret_cast<Value*>(i::HandleScope::CreateHandle(
+              isolate, isolate->heap()->undefined_value())));
+    }
+  }
+
+  PREPARE_FOR_EXECUTION_PRIMITIVE(context, DictionarySchema, Get, bool);
+  i::Handle<i::DictionarySchema> schema = Utils::OpenHandle(this);
+  int length = schema->length();
+  i::Handle<i::JSReceiver> receiver = Utils::OpenHandle(*object);
+  for (; *index < length; (*index)++) {
+    i::Handle<i::Object> key(schema->get(*index), isolate);
+    bool success = false;
+    i::LookupIterator it =
+        i::LookupIterator::PropertyOrElement(isolate, receiver, key, &success);
+    CHECK(success);
+    i::Handle<i::Object> value;
+    if (!i::Object::GetProperty(&it).ToHandle(&value)) {
+      RETURN_ON_FAILED_EXECUTION_PRIMITIVE(bool);
+    }
+
+    // TODO(jbroman): Hack to escape the handle scope.
+    Value* slot = out[*index].val_;
+    *reinterpret_cast<i::Object**>(slot) = *value;
+
+    const bool should_pause =
+        (value->IsPrimitive() && !(continue_filter & kValueFilterPrimitives)) ||
+        (value->IsJSReceiver() && !(continue_filter & kValueFilterObjects));
+    if (should_pause) {
+      (*index)++;
+      return Just(false);
+    }
+  }
+
+  return Just(true);
+}
 
 #define SET_FIELD_WRAPPED(obj, setter, cdata) do {                      \
     i::Handle<i::Object> foreign = FromCData(obj->GetIsolate(), cdata); \