add original source

source/listing_6.10.cpp

@@ -0,0 +1,44 @@
+template<typename T>
+class threadsafe_queue
+{
+private:
+    std::unique_ptr<node> try_pop_head()
+    {
+        std::lock_guard<std::mutex> head_lock(head_mutex);
+        if(head.get()==get_tail())
+        {
+            return std::unique_ptr<node>();
+        }
+        return pop_head();
+    }
+
+    std::unique_ptr<node> try_pop_head(T& value)
+    {
+        std::lock_guard<std::mutex> head_lock(head_mutex);
+        if(head.get()==get_tail())
+        {
+            return std::unique_ptr<node>();
+        }
+        value=std::move(*head->data);
+        return pop_head();
+    }
+
+public:
+    std::shared_ptr<T> try_pop()
+    {
+        std::unique_ptr<node> const old_head=try_pop_head();
+        return old_head?old_head->data:std::shared_ptr<T>();
+    }
+
+    bool try_pop(T& value)
+    {
+        std::unique_ptr<node> const old_head=try_pop_head(value);
+        return old_head;
+    }
+
+    void empty()
+    {
+        std::lock_guard<std::mutex> head_lock(head_mutex);
+        return (head==get_tail());
+    }
+};