up

include/yaml-cpp/node/detail/memory.h

@@ -25,6 +25,7 @@ class YAML_CPP_API memory {
   memory() : m_nodes{} {}
   node& create_node();
   void merge(const memory& rhs);
+  size_t size() const;
 
  private:
   using Nodes = std::set<shared_node>;

src/memory.cpp

@@ -9,6 +9,10 @@ void memory_holder::merge(memory_holder& rhs) {
   if (m_pMemory == rhs.m_pMemory)
     return;
 
+  if (m_pMemory->size() < rhs.m_pMemory->size()) {
+    std::swap(m_pMemory, rhs.m_pMemory);
+  }
+
   m_pMemory->merge(*rhs.m_pMemory);
   rhs.m_pMemory = m_pMemory;
 }
@@ -22,5 +26,9 @@ node& memory::create_node() {
 void memory::merge(const memory& rhs) {
   m_nodes.insert(rhs.m_nodes.begin(), rhs.m_nodes.end());
 }
+
+size_t memory::size() const {
+    return m_nodes.size();
+}
 }  // namespace detail
 }  // namespace YAML