add original source

source/listing_7.18.cpp

@@ -0,0 +1,20 @@
+template<typename T>
+class lock_free_queue
+{
+private:
+    static void increase_external_count(
+        std::atomic<counted_node_ptr>& counter,
+        counted_node_ptr& old_counter)
+    {
+        counted_node_ptr new_counter;
+        do
+        {
+            new_counter=old_counter;
+            ++new_counter.external_count;
+        }
+        while(!counter.compare_exchange_strong(
+                  old_counter,new_counter,
+                  std::memory_order_acquire,std::memory_order_relaxed));
+        old_counter.external_count=new_counter.external_count;
+    }
+};