Load extensions features file separately when needed

chrome/common/extensions/features/base_feature_provider.cc

 // Copyright (c) 2012 The Chromium 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 "chrome/common/extensions/features/base_feature_provider.h"
 
 #include "base/json/json_reader.h"
 #include "base/lazy_instance.h"
 #include "chrome/common/extensions/features/api_feature.h"
 #include "chrome/common/extensions/features/complex_feature.h"
 #include "chrome/common/extensions/features/manifest_feature.h"
 #include "chrome/common/extensions/features/permission_feature.h"
 #include "grit/common_resources.h"
 #include "ui/base/resource/resource_bundle.h"
 
 namespace extensions {
 
 namespace {
 
 template<class FeatureClass>
 SimpleFeature* CreateFeature() {
   return new FeatureClass();
 }
 
-struct Static {
-  Static()
-      : api_features(
-            LoadProvider("api",
-                         &CreateFeature<APIFeature>,
-                         IDR_EXTENSION_API_FEATURES)),
-        manifest_features(
-            LoadProvider("manifest",
-                         &CreateFeature<ManifestFeature>,
-                         IDR_EXTENSION_MANIFEST_FEATURES)),
-        permission_features(
-            LoadProvider("permissions",
-                         &CreateFeature<PermissionFeature>,
-                         IDR_EXTENSION_PERMISSION_FEATURES)) {
+struct LazyFeatureProvider : public FeatureProvider {

[not at google - send to devlin, 2013/04/10 02:06:22]

I don't think this needs to be a struct. The member variables should be private
(and be name_, factory_, etc too).

[cduvall, 2013/04/10 02:26:12]

Done.

+  LazyFeatureProvider(const std::string& name_,
+                      BaseFeatureProvider::FeatureFactory factory_,
+                      int resource_id_)
+      : name(name_),
+        factory(factory_),
+        resource_id(resource_id_) {
   }
 
-  scoped_ptr<BaseFeatureProvider> api_features;
-  scoped_ptr<BaseFeatureProvider> manifest_features;
-  scoped_ptr<BaseFeatureProvider> permission_features;
+  BaseFeatureProvider* GetBaseFeatureProvider() {
+    if (!features)
+      features.reset(LoadProvider(name, factory, resource_id).release());

[not at google - send to devlin, 2013/04/10 02:06:22]

shouldn't need the release/reset here. features = LoadProvider(...) should work.

[cduvall, 2013/04/10 02:26:12]

Done.

+    return features.get();
+  }
+
+  virtual Feature* GetFeature(const std::string& name) {
+    return GetBaseFeatureProvider()->GetFeature(name);
+  }
+
+  std::string name;
+  BaseFeatureProvider::FeatureFactory factory;
+  int resource_id;
+  scoped_ptr<BaseFeatureProvider> features;
 
  private:
   scoped_ptr<BaseFeatureProvider> LoadProvider(
       const std::string& debug_string,
       BaseFeatureProvider::FeatureFactory factory,
       int resource_id) {
     const std::string& features_file =
         ResourceBundle::GetSharedInstance().GetRawDataResource(
             resource_id).as_string();
     int error_code = 0;
     std::string error_message;
     scoped_ptr<Value> value(base::JSONReader::ReadAndReturnError(
         features_file, base::JSON_PARSE_RFC,
         &error_code, &error_message));
     DCHECK(value) << "Could not load features: " << debug_string << " "
                   << error_message;
     scoped_ptr<DictionaryValue> value_as_dict;
     if (value) {
       CHECK(value->IsType(Value::TYPE_DICTIONARY)) << debug_string;
       value_as_dict.reset(static_cast<DictionaryValue*>(value.release()));
     } else {
       // http://crbug.com/176381
       value_as_dict.reset(new DictionaryValue());
     }
     return make_scoped_ptr(new BaseFeatureProvider(*value_as_dict, factory));
   }
 };
 
+struct Static {
+  Static() {
+    lazy_feature_providers["api"] = linked_ptr<LazyFeatureProvider>(

[not at google - send to devlin, 2013/04/10 02:06:22]

make_linked_ptr?

[cduvall, 2013/04/10 02:26:12]

Done.

+        new LazyFeatureProvider("api",
+                                &CreateFeature<APIFeature>,
+                                IDR_EXTENSION_API_FEATURES));
+    lazy_feature_providers["permission"] = linked_ptr<LazyFeatureProvider>(
+        new LazyFeatureProvider("permission",
+                                &CreateFeature<PermissionFeature>,
+                                IDR_EXTENSION_PERMISSION_FEATURES));
+    lazy_feature_providers["manifest"] = linked_ptr<LazyFeatureProvider>(
+        new LazyFeatureProvider("manifest",
+                                &CreateFeature<ManifestFeature>,
+                                IDR_EXTENSION_MANIFEST_FEATURES));
+  }
+
+  LazyFeatureProvider* LazyGetFeatures(const std::string& name) {
+    CHECK(lazy_feature_providers.count(name) > 0);
+    return lazy_feature_providers[name].get();

[not at google - send to devlin, 2013/04/10 02:06:22]

use find, it = lazy_feature_providers.find(..); CHECK(it != end()); return
it->second;

[cduvall, 2013/04/10 02:26:12]

Done.

+  }
+
+  BaseFeatureProvider* GetFeatures(const std::string& name) {
+    return LazyGetFeatures(name)->GetBaseFeatureProvider();
+  }
+
+  typedef std::map<std::string, linked_ptr<LazyFeatureProvider> >
+      LazyFeatureProviderMap;
+  LazyFeatureProviderMap lazy_feature_providers;
+};
+
+base::LazyInstance<Static> g_static = LAZY_INSTANCE_INITIALIZER;
+
 bool ParseFeature(const DictionaryValue* value,
                   const std::string& name,
                   SimpleFeature* feature) {
   feature->set_name(name);
   std::string error = feature->Parse(value);
   if (!error.empty())
     LOG(ERROR) << error;
   return error.empty();
 }
 
-base::LazyInstance<Static> g_static = LAZY_INSTANCE_INITIALIZER;
-
 }  // namespace
 
 BaseFeatureProvider::BaseFeatureProvider(const DictionaryValue& root,
                                          FeatureFactory factory)
     : factory_(factory ? factory :
                static_cast<FeatureFactory>(&CreateFeature<SimpleFeature>)) {
   for (DictionaryValue::Iterator iter(root); iter.HasNext(); iter.Advance()) {
     if (iter.value().GetType() == Value::TYPE_DICTIONARY) {
       linked_ptr<SimpleFeature> feature((*factory_)());
 
@@ skipping 36 matching lines @@
       LOG(ERROR) << iter.key() << ": Feature description must be dictionary or"
                  << " list of dictionaries.";
     }
   }
 }
 
 BaseFeatureProvider::~BaseFeatureProvider() {
 }
 
 // static
-BaseFeatureProvider* BaseFeatureProvider::GetAPIFeatures() {
-  return g_static.Get().api_features.get();
+BaseFeatureProvider* BaseFeatureProvider::GetFeaturesByName(
+    const std::string& name) {
+  return g_static.Get().GetFeatures(name);
 }
 
 // static
-BaseFeatureProvider* BaseFeatureProvider::GetManifestFeatures() {
-  return g_static.Get().manifest_features.get();
-}
-
-// static
-BaseFeatureProvider* BaseFeatureProvider::GetPermissionFeatures() {
-  return g_static.Get().permission_features.get();
+FeatureProvider* BaseFeatureProvider::LazyGetFeaturesByName(
+    const std::string& name) {
+  return g_static.Get().LazyGetFeatures(name);
 }
 
 std::set<std::string> BaseFeatureProvider::GetAllFeatureNames() const {
   std::set<std::string> result;
   for (FeatureMap::const_iterator iter = features_.begin();
        iter != features_.end(); ++iter) {
     result.insert(iter->first);
   }
   return result;
 }
 
 Feature* BaseFeatureProvider::GetFeature(const std::string& name) {
   FeatureMap::iterator iter = features_.find(name);
   if (iter != features_.end())
     return iter->second.get();
   else
     return NULL;
 }
 
 }  // namespace