chapter 3 code

ch3/hierarchical.cpp

@@ -0,0 +1,57 @@
+#include <mutex>
+#include <stdexcept>
+#include <climits>
+
+class hierarchical_mutex
+{
+    std::mutex internal_mutex;
+    unsigned long const hierarchy_value;
+    unsigned long previous_hierarchy_value;
+    static thread_local unsigned long this_thread_hierarchy_value;
+
+    void check_for_hierarchy_violation()
+    {
+        if(this_thread_hierarchy_value <= hierarchy_value)
+        {
+            throw std::logic_error("mutex hierarchy violated");
+        }
+    }
+    void update_hierarchy_value()
+    {
+        previous_hierarchy_value=this_thread_hierarchy_value;
+        this_thread_hierarchy_value=hierarchy_value;
+    }
+public:
+    explicit hierarchical_mutex(unsigned long value):
+        hierarchy_value(value),
+        previous_hierarchy_value(0)
+    {}
+    void lock()
+    {
+        check_for_hierarchy_violation();
+        internal_mutex.lock();
+        update_hierarchy_value();
+    }
+    void unlock()
+    {
+        this_thread_hierarchy_value=previous_hierarchy_value;
+        internal_mutex.unlock();
+    }
+    bool try_lock()
+    {
+        check_for_hierarchy_violation();
+        if(!internal_mutex.try_lock())
+            return false;
+        update_hierarchy_value();
+        return true;
+    }
+};
+thread_local unsigned long
+    hierarchical_mutex::this_thread_hierarchy_value(ULONG_MAX);       
+
+int main()
+{
+    hierarchical_mutex m1(42);
+    hierarchical_mutex m2(2000);
+    
+}