Merge branch 'better-concurrency' into next

src/core/receiver/concurrent_map.h

@@ -36,52 +36,48 @@ template <typename Data>
  */
 class Concurrent_Map
 {
-    typedef typename std::map<int, Data>::iterator Data_iterator;  // iterator is scope dependent
 public:
     void write(int key, Data const& data)
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        Data_iterator data_iter;
-        data_iter = the_map.find(key);
+        std::lock_guard<std::mutex> lock(the_mutex);
+        auto data_iter = the_map.find(key);
         if (data_iter != the_map.end())
             {
                 data_iter->second = data;  // update
             }
         else
             {
-                the_map.insert(std::pair<int, Data>(key, data));  // insert SILENTLY fails if the item already exists in the map!
+                the_map.insert(std::pair<int, Data>(key, data));  // insert does not overwrite if the item already exists in the map!
             }
-        lock.unlock();
     }
 
-    std::map<int, Data> get_map_copy()
+    std::map<int, Data> get_map_copy() const&
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        std::map<int, Data> map_aux = the_map;
-        lock.unlock();
-        return map_aux;
+        std::lock_guard<std::mutex> lock(the_mutex);
+        return the_map;  // This implicitly creates a copy
     }
 
-    size_t size()
+    std::map<int, Data> get_map_copy() &&
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        size_t size_ = the_map.size();
-        lock.unlock();
-        return size_;
+        std::lock_guard<std::mutex> lock(the_mutex);
+        return std::move(the_map);
     }
 
-    bool read(int key, Data& p_data)
+    size_t size() const
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        Data_iterator data_iter;
-        data_iter = the_map.find(key);
+        std::lock_guard<std::mutex> lock(the_mutex);
+        return the_map.size();
+    }
+
+    bool read(int key, Data& p_data) const
+    {
+        std::lock_guard<std::mutex> lock(the_mutex);
+        auto data_iter = the_map.find(key);
         if (data_iter != the_map.end())
             {
                 p_data = data_iter->second;
-                lock.unlock();
                 return true;
             }
-        lock.unlock();
         return false;
     }
 

src/core/receiver/concurrent_queue.h

@@ -19,9 +19,10 @@
 
 #include <chrono>
 #include <condition_variable>
+#include <cstddef>
 #include <mutex>
 #include <queue>
-#include <thread>
+#include <utility>
 
 /** \addtogroup Core
  * \{ */
@@ -33,48 +34,53 @@ template <typename Data>
 
 /*!
  * \brief This class implements a thread-safe std::queue
- *
- * Thread-safe object queue which uses the library
- * boost_thread to perform MUTEX based on the code available at
- * https://www.justsoftwaresolutions.co.uk/threading/implementing-a-thread-safe-queue-using-condition-variables.html
  */
 class Concurrent_Queue
 {
 public:
-    void push(Data const& data)
+    void push(const Data& data)
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
+        {
+            std::lock_guard<std::mutex> lock(the_mutex);
             the_queue.push(data);
-        lock.unlock();
+        }
         the_condition_variable.notify_one();
     }
 
-    bool empty() const
+    void push(Data&& data)
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        return the_queue.empty();
+        {
+            std::lock_guard<std::mutex> lock(the_mutex);
+            the_queue.push(std::move(data));
+        }
+        the_condition_variable.notify_one();
     }
 
-    size_t size() const
+    bool empty() const noexcept
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
+        return size() == 0;
+    }
+
+    size_t size() const noexcept
+    {
+        std::lock_guard<std::mutex> lock(the_mutex);
         return the_queue.size();
     }
 
     void clear()
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
-        the_queue = std::queue<Data>();
+        std::lock_guard<std::mutex> lock(the_mutex);
+        std::queue<Data>().swap(the_queue);
     }
 
     bool try_pop(Data& popped_value)
     {
-        std::unique_lock<std::mutex> lock(the_mutex);
+        std::lock_guard<std::mutex> lock(the_mutex);
         if (the_queue.empty())
             {
                 return false;
             }
-        popped_value = the_queue.front();
+        popped_value = std::move(the_queue.front());
         the_queue.pop();
         return true;
     }
@@ -82,26 +88,21 @@ public:
     void wait_and_pop(Data& popped_value)
     {
         std::unique_lock<std::mutex> lock(the_mutex);
-        while (the_queue.empty())
-            {
-                the_condition_variable.wait(lock);
-            }
-        popped_value = the_queue.front();
+        the_condition_variable.wait(lock, [this] { return !the_queue.empty(); });
+        popped_value = std::move(the_queue.front());
         the_queue.pop();
     }
 
     bool timed_wait_and_pop(Data& popped_value, int wait_ms)
     {
         std::unique_lock<std::mutex> lock(the_mutex);
-        if (the_queue.empty())
-            {
-                the_condition_variable.wait_for(lock, std::chrono::milliseconds(wait_ms));
-                if (the_queue.empty())
+        if (!the_condition_variable.wait_for(lock,
+                std::chrono::milliseconds(wait_ms),
+                [this] { return !the_queue.empty(); }))
             {
                 return false;
             }
-            }
-        popped_value = the_queue.front();
+        popped_value = std::move(the_queue.front());
         the_queue.pop();
         return true;
     }