Simplified memory management in class Json.

By making JsonImpl a friend class and providing a private constructor
that it can call to create new Json objects that initialize their impl_
member in the constructor, it becomes possible to store newly created
Json objects directly into dictionaries_ to simplify program flow.

R=rouslan@chromium.org
BUG=

Review URL: https://codereview.appspot.com/113480043

git-svn-id: http://libaddressinput.googlecode.com/svn/trunk@318 38ededc0-08b8-5190-f2ac-b31f878777ad

2 files changed, 13 insertions, 12 deletions

diff --git a/cpp/src/util/json.cc b/cpp/src/util/json.cc
index 14a9d11..ef3056b 100644
--- a/cpp/src/util/json.cc
+++ b/cpp/src/util/json.cc
@@ -90,17 +90,11 @@ class Json::JsonImpl {
       return false;
     }
 
-    Json* sub_dictionary = new Json;
-    sub_dictionary->impl_.reset(new JsonImpl(&member->value));
-    bool inserted =
-        dictionaries_.insert(std::make_pair(key, sub_dictionary)).second;
-    // Cannot do work inside of assert(), because the compiler can optimize it
-    // away.
-    assert(inserted);
-    // Avoid unused variable warning when assert() is optimized away.
-    (void)inserted;
-
-    *value = sub_dictionary;
+    std::pair<std::map<std::string, const Json*>::iterator, bool> result =
+        dictionaries_.insert(
+            std::make_pair(key, new Json(new JsonImpl(&member->value))));
+    assert(result.second);
+    *value = result.first->second;
     return true;
   }
 
@@ -143,7 +137,7 @@ class Json::JsonImpl {
   DISALLOW_COPY_AND_ASSIGN(JsonImpl);
 };
 
-Json::Json() {}
+Json::Json() : impl_() {}
 
 Json::~Json() {}
 
@@ -173,5 +167,7 @@ bool Json::GetDictionaryValueForKey(const std::string& key,
   return impl_->GetDictionaryValueForKey(key, value);
 }
 
+Json::Json(JsonImpl* impl) : impl_(impl) {}
+
 }  // namespace addressinput
 }  // namespace i18n
diff --git a/cpp/src/util/json.h b/cpp/src/util/json.h
index 1d66aeb..42cd331 100644
--- a/cpp/src/util/json.h
+++ b/cpp/src/util/json.h
@@ -58,6 +58,11 @@ class Json {
 
  private:
   class JsonImpl;
+  friend class JsonImpl;
+
+  // Constructor to be called by JsonImpl.
+  explicit Json(JsonImpl* impl);
+
   scoped_ptr<JsonImpl> impl_;
 
   DISALLOW_COPY_AND_ASSIGN(Json);