[builtins] move String.prototype[@@iterator] to C++ builtin

src/factory.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/factory.h"
 
 #include "src/accessors.h"
 #include "src/allocation-site-scopes.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
@@ skipping 589 matching lines @@
   return result;
 }
 
 
 Handle<String> Factory::NewProperSubString(Handle<String> str,
                                            int begin,
                                            int end) {
 #if VERIFY_HEAP
   if (FLAG_verify_heap) str->StringVerify();
 #endif
-  DCHECK(begin > 0 || end < str->length());
+  DCHECK(begin > 0 || end <= str->length());

[Benedikt Meurer, 2016/09/19 04:05:18]

This still looks wrong to me. Please undo this change (and maybe introduce a
helper NewSurrogatePairString for your use case). See comments on the builtins.

[caitp, 2016/09/19 16:03:05]

Done.

 
   str = String::Flatten(str);
 
   int length = end - begin;
   if (length <= 0) return empty_string();
   if (length == 1) {
     return LookupSingleCharacterStringFromCode(str->Get(begin));
   }
   if (length == 2) {
     // Optimization for 2-byte strings often used as keys in a decompression
@@ skipping 106 matching lines @@
   Handle<Map> map = native_source_string_map();
   Handle<ExternalOneByteString> external_string =
       New<ExternalOneByteString>(map, OLD_SPACE);
   external_string->set_length(static_cast<int>(length));
   external_string->set_hash_field(String::kEmptyHashField);
   external_string->set_resource(resource);
 
   return external_string;
 }
 
+Handle<JSStringIterator> Factory::NewJSStringIterator(Handle<String> string) {
+  Handle<Map> map(isolate()->native_context()->string_iterator_map());

[Benedikt Meurer, 2016/09/19 04:05:18]

Nit: Handle<Map> map(isolate()->native_context()->string_iterator_map(),
                     isolate());

[caitp, 2016/09/19 16:03:05]

Done.

+  Handle<String> flat_string = String::Flatten(string);
+  Handle<JSStringIterator> iterator =
+      Handle<JSStringIterator>::cast(NewJSObjectFromMap(map));
+  iterator->set_string(*flat_string);
+  iterator->set_index(0);
+
+  return iterator;
+}
 
 Handle<Symbol> Factory::NewSymbol() {
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateSymbol(),
       Symbol);
 }
 
 
 Handle<Symbol> Factory::NewPrivateSymbol() {
@@ skipping 978 matching lines @@
 
 Handle<JSDataView> Factory::NewJSDataView() {
   Handle<JSFunction> data_view_fun(
       isolate()->native_context()->data_view_fun());
   CALL_HEAP_FUNCTION(
       isolate(),
       isolate()->heap()->AllocateJSObject(*data_view_fun),
       JSDataView);
 }
 
+Handle<JSIteratorResult> Factory::NewJSIteratorResult(Handle<Object> value,
+                                                      bool done) {
+  Handle<Map> map(isolate()->native_context()->iterator_result_map());
+  Handle<JSIteratorResult> js_iter_result =
+      Handle<JSIteratorResult>::cast(NewJSObjectFromMap(map));
+  js_iter_result->set_value(*value);
+  js_iter_result->set_done(*ToBoolean(done));
+  return js_iter_result;
+}
 
 Handle<JSMap> Factory::NewJSMap() {
   Handle<Map> map(isolate()->native_context()->js_map_map());
   Handle<JSMap> js_map = Handle<JSMap>::cast(NewJSObjectFromMap(map));
   JSMap::Initialize(js_map, isolate());
   return js_map;
 }
 
 
 Handle<JSSet> Factory::NewJSSet() {
@@ skipping 786 matching lines @@
     Handle<AccessorInfo> prototype =
         Accessors::FunctionPrototypeInfo(isolate(), attribs);
     AccessorConstantDescriptor d(Handle<Name>(Name::cast(prototype->name())),
                                  prototype, attribs);
     map->AppendDescriptor(&d);
   }
 }
 
 }  // namespace internal
 }  // namespace v8