Simplify accesses to Script::line_ends

src/api.cc

 // Copyright 2012 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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 8862 matching lines @@
 
 int DebugInterface::Script::LineOffset() const {
   return Utils::OpenHandle(this)->line_offset();
 }
 
 int DebugInterface::Script::ColumnOffset() const {
   return Utils::OpenHandle(this)->column_offset();
 }
 
 std::vector<int> DebugInterface::Script::LineEnds() const {
-  i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
+  i::Handle<i::Script> script = Utils::OpenHandle(this);
+  i::Isolate* isolate = script->GetIsolate();
   i::HandleScope scope(isolate);
-  i::Script::InitLineEnds(Utils::OpenHandle(this));
-  i::Handle<i::Object> line_ends_obj(Utils::OpenHandle(this)->line_ends(),
-                                     isolate);
+  i::Script::InitLineEnds(script);
+  CHECK(script->line_ends()->IsFixedArray());
   std::vector<int> result;
-  if (!line_ends_obj->IsFixedArray()) return result;
-  i::Handle<i::FixedArray> line_ends =
-      i::Handle<i::FixedArray>::cast(line_ends_obj);
+  i::Handle<i::FixedArray> line_ends(i::FixedArray::cast(script->line_ends()));
   for (int i = 0; i < line_ends->length(); ++i) {
-    i::Handle<i::Object> line_end = i::FixedArray::get(*line_ends, i, isolate);
-    if (line_end->IsSmi()) {
-      result.push_back(i::Handle<i::Smi>::cast(line_end)->value());
-    } else {
-      result.push_back(0);
-    }
+    i::Smi* line_end = i::Smi::cast(line_ends->get(i));
+    result.push_back(line_end->value());

[Yang, 2016/11/09 09:29:18]

since we already know the resulting size of the vector, wouldn't it make sense
to reserve the capacity upfront?

   }
   return result;
 }
 
 MaybeLocal<String> DebugInterface::Script::Name() const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   i::HandleScope handle_scope(isolate);
   i::Handle<i::Script> script = Utils::OpenHandle(this);
   i::Handle<i::Object> value(script->name(), isolate);
   if (!value->IsString()) return MaybeLocal<String>();
@@ skipping 861 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8