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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 12:34:54 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-28 12:34:54 +0000
commit0915b3ef56dfac3113cce55a59a5765dc94976be (patch)
treea8fea11d50b4f083e1bf0f90025ece7f0824784a /lib/base/lazy-init.hpp
parentInitial commit. (diff)
downloadicinga2-0915b3ef56dfac3113cce55a59a5765dc94976be.tar.xz
icinga2-0915b3ef56dfac3113cce55a59a5765dc94976be.zip
Adding upstream version 2.13.6.upstream/2.13.6upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--lib/base/lazy-init.hpp72
1 files changed, 72 insertions, 0 deletions
diff --git a/lib/base/lazy-init.hpp b/lib/base/lazy-init.hpp
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+/* Icinga 2 | (c) 2012 Icinga GmbH | GPLv2+ */
+
+#ifndef LAZY_INIT
+#define LAZY_INIT
+
+#include <atomic>
+#include <functional>
+#include <mutex>
+#include <utility>
+
+namespace icinga
+{
+
+/**
+ * Lazy object initialization abstraction inspired from
+ * <https://docs.microsoft.com/en-us/dotnet/api/system.lazy-1?view=netframework-4.7.2>.
+ *
+ * @ingroup base
+ */
+template<class T>
+class LazyInit
+{
+public:
+ inline
+ LazyInit(std::function<T()> initializer = []() { return T(); }) : m_Initializer(std::move(initializer))
+ {
+ m_Underlying.store(nullptr, std::memory_order_release);
+ }
+
+ LazyInit(const LazyInit&) = delete;
+ LazyInit(LazyInit&&) = delete;
+ LazyInit& operator=(const LazyInit&) = delete;
+ LazyInit& operator=(LazyInit&&) = delete;
+
+ inline
+ ~LazyInit()
+ {
+ auto ptr (m_Underlying.load(std::memory_order_acquire));
+
+ if (ptr != nullptr) {
+ delete ptr;
+ }
+ }
+
+ inline
+ T& Get()
+ {
+ auto ptr (m_Underlying.load(std::memory_order_acquire));
+
+ if (ptr == nullptr) {
+ std::unique_lock<std::mutex> lock (m_Mutex);
+
+ ptr = m_Underlying.load(std::memory_order_acquire);
+
+ if (ptr == nullptr) {
+ ptr = new T(m_Initializer());
+ m_Underlying.store(ptr, std::memory_order_release);
+ }
+ }
+
+ return *ptr;
+ }
+
+private:
+ std::function<T()> m_Initializer;
+ std::mutex m_Mutex;
+ std::atomic<T*> m_Underlying;
+};
+
+}
+
+#endif /* LAZY_INIT */