Made the 'data' member optional in node_ref - it's only created on-demand, so we…

Made the 'data' member optional in node_ref - it's only created on-demand, so we don't waste extra memory every time we do Value tmp = v;

include/yaml-cpp/value/detail/node_data.h

@@ -41,6 +41,9 @@ namespace YAML
 			node& get(node& key, shared_memory_holder pMemory);
 			bool remove(node& key, shared_memory_holder pMemory);
 			
+		public:
+			static std::string empty_scalar;
+			
 		private:
 			void convert_sequence_to_map(shared_memory_holder pMemory);
 			

include/yaml-cpp/value/detail/node_ref.h

@@ -19,27 +19,30 @@ namespace YAML
 		class node_ref: private boost::noncopyable
 		{
 		public:
-			node_ref(): m_pData(new node_data) {}
+			node_ref() {}
 			
-			ValueType::value type() const { return m_pData->type(); }
-			const std::string& scalar() const { return m_pData->scalar(); }
+			ValueType::value type() const { return m_pData ? m_pData->type() : ValueType::Undefined; }
+			const std::string& scalar() const { return m_pData ? m_pData->scalar() : node_data::empty_scalar; }
 			
 			void set_data(const node_ref& rhs) { m_pData = rhs.m_pData; }
 			
-			void set_type(ValueType::value type) { m_pData->set_type(type); }
-			void set_null() { m_pData->set_null(); }
-			void set_scalar(const std::string& scalar) { m_pData->set_scalar(scalar); }
+			void set_type(ValueType::value type) { ensure_data_exists(); m_pData->set_type(type); }
+			void set_null() { ensure_data_exists(); m_pData->set_null(); }
+			void set_scalar(const std::string& scalar) { ensure_data_exists(); m_pData->set_scalar(scalar); }
 			
-			void append(node& node, shared_memory_holder pMemory) { m_pData->append(node, pMemory); }
+			void append(node& node, shared_memory_holder pMemory) { ensure_data_exists(); m_pData->append(node, pMemory); }
 			
 			// indexing
-			template<typename Key> node& get(const Key& key, shared_memory_holder pMemory) const { return static_cast<const node_data&>(*m_pData).get(key, pMemory); }
-			template<typename Key> node& get(const Key& key, shared_memory_holder pMemory) { return m_pData->get(key, pMemory); }
-			template<typename Key> bool remove(const Key& key, shared_memory_holder pMemory) { return m_pData->remove(key, pMemory); }
+			template<typename Key> node& get(const Key& key, shared_memory_holder pMemory) const { return m_pData ? static_cast<const node_data&>(*m_pData).get(key, pMemory) : pMemory->create_node(); }
+			template<typename Key> node& get(const Key& key, shared_memory_holder pMemory) { ensure_data_exists(); return m_pData->get(key, pMemory); }
+			template<typename Key> bool remove(const Key& key, shared_memory_holder pMemory) { return m_pData ? m_pData->remove(key, pMemory) : false; }
 			
-			node& get(node& key, shared_memory_holder pMemory) const { return static_cast<const node_data&>(*m_pData).get(key, pMemory); }
-			node& get(node& key, shared_memory_holder pMemory) { return m_pData->get(key, pMemory); }
-			bool remove(node& key, shared_memory_holder pMemory) { return m_pData->remove(key, pMemory); }
+			node& get(node& key, shared_memory_holder pMemory) const { return m_pData ? static_cast<const node_data&>(*m_pData).get(key, pMemory) : pMemory->create_node(); }
+			node& get(node& key, shared_memory_holder pMemory) { ensure_data_exists(); return m_pData->get(key, pMemory); }
+			bool remove(node& key, shared_memory_holder pMemory) { return m_pData ? m_pData->remove(key, pMemory) : false; }
+			
+		private:
+			void ensure_data_exists() { if(!m_pData) m_pData.reset(new node_data); }
 			
 		private:
 			shared_node_data m_pData;

include/yaml-cpp/value/impl.h

@@ -15,7 +15,6 @@ namespace YAML
 {
 	inline Value::Value(): m_pMemory(new detail::memory_holder), m_pNode(&m_pMemory->create_node())
 	{
-		m_pNode->set_null();
 	}
 	
 	inline Value::Value(ValueType::value type): m_pMemory(new detail::memory_holder), m_pNode(&m_pMemory->create_node())

src/value/detail/node_data.cpp

@@ -8,6 +8,8 @@ namespace YAML
 {
 	namespace detail
 	{
+		std::string node_data::empty_scalar;
+
 		node_data::node_data(): m_isDefined(false), m_type(ValueType::Null)
 		{
 		}