use predicate of conditional::wait instead of hand-crafted loop

Author: lonvia

db-copy.cpp

@@ -29,17 +29,12 @@ void db_copy_thread_t::add_buffer(std::unique_ptr<db_cmd_t> &&buffer)
 {
     assert(m_worker.joinable()); // thread must not have been finished
 
-    for (;;) {
-        std::unique_lock<std::mutex> lock(m_queue_mutex);
-        if (m_worker_queue.size() >= db_cmd_copy_t::Max_buffers) {
-            m_queue_full_cond.wait(lock);
-            continue;
-        }
+    std::unique_lock<std::mutex> lock(m_queue_mutex);
+    m_queue_full_cond.wait(lock,
+            [&]{ return m_worker_queue.size() < db_cmd_copy_t::Max_buffers; });
 
-        m_worker_queue.push_back(std::move(buffer));
-        m_queue_cond.notify_one();
-        break;
-    }
+    m_worker_queue.push_back(std::move(buffer));
+    m_queue_cond.notify_one();
 }
 
 void db_copy_thread_t::sync_and_wait()
@@ -69,10 +64,7 @@ void db_copy_thread_t::worker_thread()
         std::unique_ptr<db_cmd_t> item;
         {
             std::unique_lock<std::mutex> lock(m_queue_mutex);
-            if (m_worker_queue.empty()) {
-                m_queue_cond.wait(lock);
-                continue;
-            }
+            m_queue_cond.wait(lock, [&]{ return !m_worker_queue.empty(); });
 
             item = std::move(m_worker_queue.front());
             m_worker_queue.pop_front();