Add singleton class

Author: dhilst

include/cloysterhpc/functions.h

@@ -16,6 +16,36 @@
 #include <type_traits>
 
 namespace cloyster {
+
+template <typename T>
+class Singleton {
+    // Private constructor to prevent direct instantiation
+    Singleton() = default;
+
+    // Static members for singleton management
+    static std::unique_ptr<T> instance;
+    static std::once_flag initFlag;
+public:
+    Singleton(Singleton&&) = delete;
+    Singleton& operator=(Singleton&&) = delete;
+    Singleton(const Singleton&) = delete;
+    Singleton& operator=(const Singleton&) = delete;
+    ~Singleton() = delete;
+
+    static void init(std::unique_ptr<T> value) {
+        std::call_once(initFlag, [&](){
+            instance = std::move(value);
+        });
+    }
+
+    static T& get() {
+        std::call_once(initFlag, []() {
+            instance = std::make_unique<T>();
+        });
+        return *instance;
+    }
+};
+
 // Globals
 extern bool dryRun;
 

src/functions.cpp

@@ -30,6 +30,13 @@ using cloyster::services::BaseRunner;
 using cloyster::services::DryRunner;
 using cloyster::services::Runner;
 
+
+template <typename T>
+std::unique_ptr<T> Singleton<T>::instance = nullptr;
+
+template <typename T>
+std::once_flag Singleton<T>::initFlag;
+
 namespace {
     std::tuple<bool, std::optional<std::string>> retrieveLine(
         boost::process::ipstream& pipe_stream,
@@ -69,14 +76,12 @@ using cloyster::services::repos::RepoManager;
 static std::unique_ptr<Cluster> clusterSingleton;
 void initClusterSingleton(std::unique_ptr<Cluster> cluster)
 {
-    assert(!clusterSingleton);
-    clusterSingleton = std::move(cluster);
+    Singleton<Cluster>::init(std::move(cluster));
 }
 
 Cluster& getClusterSingleton()
 {
-    assert(clusterSingleton);
-    return *clusterSingleton;
+    return Singleton<Cluster>::get();
 }
 
 std::shared_ptr<RepoManager> getRepoManager(const OS& osinfo)