Add a maximum number of forward/backward time steps that can be queued

scwx-qt/source/scwx/qt/util/queue_counter.cpp

@@ -0,0 +1,49 @@
+#include <scwx/qt/util/queue_counter.hpp>
+
+#include <atomic>
+
+namespace scwx::qt::util
+{
+
+class QueueCounter::Impl
+{
+public:
+   explicit Impl(size_t maxCount) : maxCount_ {maxCount} {}
+
+   const size_t        maxCount_;
+   std::atomic<size_t> count_ {0};
+};
+
+QueueCounter::QueueCounter(size_t maxCount) :
+    p {std::make_unique<Impl>(maxCount)}
+{
+}
+
+QueueCounter::~QueueCounter() = default;
+
+bool QueueCounter::add()
+{
+   const size_t count = p->count_.fetch_add(1);
+   // Must be >= (not ==) to avoid race conditions
+   if (count >= p->maxCount_)
+   {
+      p->count_.fetch_sub(1);
+      return false;
+   }
+   else
+   {
+      return true;
+   }
+}
+
+void QueueCounter::remove()
+{
+   p->count_.fetch_sub(1);
+}
+
+bool QueueCounter::is_lock_free()
+{
+   return p->count_.is_lock_free();
+}
+
+} // namespace scwx::qt::util