src: minor refactor of node_trace_events.cc

Avoid unnecessary copies/extra operations & align with our style guide, and add protection against throwing getters. PR-URL: #21867 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com> Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>

Author: addaleax

src/node_trace_events.cc

@@ -25,7 +25,7 @@ class NodeCategorySet : public BaseObject {
  static void Enable(const FunctionCallbackInfo<Value>& args);
  static void Disable(const FunctionCallbackInfo<Value>& args);
 
- const std::set<std::string>& GetCategories() { return categories_; }
+ const std::set<std::string>& GetCategories() const { return categories_; }
 
  void MemoryInfo(MemoryTracker* tracker) const override {
  tracker->TrackThis(this);
@@ -37,8 +37,8 @@ class NodeCategorySet : public BaseObject {
  private:
  NodeCategorySet(Environment* env,
  Local<Object> wrap,
- std::set<std::string> categories) :
- BaseObject(env, wrap), categories_(categories) {
+ std::set<std::string>&& categories) :
+ BaseObject(env, wrap), categories_(std::move(categories)) {
  MakeWeak();
  }
 
@@ -52,12 +52,14 @@ void NodeCategorySet::New(const FunctionCallbackInfo<Value>& args) {
  CHECK(args[0]->IsArray());
  Local<Array> cats = args[0].As<Array>();
  for (size_t n = 0; n < cats->Length(); n++) {
- Local<Value> category = cats->Get(env->context(), n).ToLocalChecked();
+ Local<Value> category;
+ if (!cats->Get(env->context(), n).ToLocal(&category)) return;
  Utf8Value val(env->isolate(), category);
+ if (!*val) return;
  categories.emplace(*val);
  }
  CHECK_NOT_NULL(env->tracing_agent());
- new NodeCategorySet(env, args.This(), categories);
+ new NodeCategorySet(env, args.This(), std::move(categories));
 }
 
 void NodeCategorySet::Enable(const FunctionCallbackInfo<Value>& args) {
@@ -91,13 +93,15 @@ void GetEnabledCategories(const FunctionCallbackInfo<Value>& args) {
  args.GetReturnValue().Set(
  String::NewFromUtf8(env->isolate(),
  categories.c_str(),
- v8::NewStringType::kNormal).ToLocalChecked());
+ v8::NewStringType::kNormal,
+ categories.size()).ToLocalChecked());
  }
 }
 
 // The tracing APIs require category groups to be pointers to long-lived
 // strings. Those strings are stored here.
-static std::unordered_set<std::string> categoryGroups;
+static std::unordered_set<std::string> category_groups;
+static Mutex category_groups_mutex;
 
 // Gets a pointer to the category-enabled flags for a tracing category group,
 // if tracing is enabled for it.
@@ -107,14 +111,15 @@ static const uint8_t* GetCategoryGroupEnabled(const char* category_group) {
 }
 
 static const char* GetCategoryGroup(Environment* env,
- const Local<Value> categoryValue) {
- CHECK(categoryValue->IsString());
+ const Local<Value> category_value) {
+ CHECK(category_value->IsString());
 
- Utf8Value category(env->isolate(), categoryValue);
+ Utf8Value category(env->isolate(), category_value);
+ Mutex::ScopedLock lock(category_groups_mutex);
  // If the value already exists in the set, insertion.first will point
  // to the existing value. Thus, this will maintain a long lived pointer
  // to the category c-string.
- auto insertion = categoryGroups.insert(category.out());
+ auto insertion = category_groups.insert(category.out());
 
  // The returned insertion is a pair whose first item is the object that was
  // inserted or that blocked the insertion and second item is a boolean
@@ -133,7 +138,7 @@ static void Emit(const FunctionCallbackInfo<Value>& args) {
  // enabled.
  const char* category_group = GetCategoryGroup(env, args[1]);
  const uint8_t* category_group_enabled =
- GetCategoryGroupEnabled(category_group);
+  GetCategoryGroupEnabled(category_group);
  if (*category_group_enabled == 0) return;
 
  // get trace_event phase
@@ -142,8 +147,8 @@ static void Emit(const FunctionCallbackInfo<Value>& args) {
 
  // get trace_event name
  CHECK(args[2]->IsString());
- Utf8Value nameValue(env->isolate(), args[2]);
- const char* name = nameValue.out();
+ Utf8Value name_value(env->isolate(), args[2]);
+ const char* name = name_value.out();
 
  // get trace_event id
  int64_t id = 0;
@@ -212,7 +217,7 @@ static void CategoryGroupEnabled(const FunctionCallbackInfo<Value>& args) {
 
  const char* category_group = GetCategoryGroup(env, args[0]);
  const uint8_t* category_group_enabled =
- GetCategoryGroupEnabled(category_group);
+  GetCategoryGroupEnabled(category_group);
  args.GetReturnValue().Set(*category_group_enabled > 0);
 }