Tools: Introduce semaphore

fairmq/tools/Semaphore.cxx

@@ -0,0 +1,50 @@
+/********************************************************************************
+ *    Copyright (C) 2019 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH    *
+ *                                                                              *
+ *              This software is distributed under the terms of the             *
+ *              GNU Lesser General Public Licence (LGPL) version 3,             *
+ *                  copied verbatim in the file "LICENSE"                       *
+ ********************************************************************************/
+
+#include "Semaphore.h"
+
+namespace fair {
+namespace mq {
+namespace tools {
+
+Semaphore::Semaphore()
+    : Semaphore(0)
+{}
+
+Semaphore::Semaphore(std::size_t initial_count)
+    : fCount(initial_count)
+{}
+
+auto Semaphore::Wait() -> void
+{
+    std::unique_lock<std::mutex> lk(fMutex);
+    if (fCount > 0) {
+        --fCount;
+    } else {
+        fCv.wait(lk, [this] { return fCount > 0; });
+        --fCount;
+    }
+}
+
+auto Semaphore::Signal() -> void
+{
+    std::unique_lock<std::mutex> lk(fMutex);
+    ++fCount;
+    lk.unlock();
+    fCv.notify_one();
+}
+
+auto Semaphore::GetCount() -> std::size_t
+{
+    std::unique_lock<std::mutex> lk(fMutex);
+    return fCount;
+}
+
+} /* namespace tools */
+} /* namespace mq */
+} /* namespace fair */