Initial commit

simpleble/dependencies/external/kvn/kvn_safe_callback.hpp

@@ -0,0 +1,66 @@
+/*
+ * SPDX-FileCopyrightText: 2022 Kevin Dewald <kevin@dewald.me>
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#ifndef KVN_SAFE_CALLBACK_HPP
+#define KVN_SAFE_CALLBACK_HPP
+
+#include <atomic>
+#include <functional>
+#include <memory>
+#include <mutex>
+
+namespace kvn {
+
+template <typename _Signature>
+class safe_callback;
+
+template <class _Res, class... _ArgTypes>
+class safe_callback<_Res(_ArgTypes...)> {
+  public:
+    safe_callback() = default;
+
+    // Remove copy constructor and copy assignment
+    safe_callback(const safe_callback&) = delete;
+    safe_callback& operator=(const safe_callback&) = delete;
+
+    virtual ~safe_callback() { unload(); };
+
+    void load(std::function<_Res(_ArgTypes...)> callback) {
+        if (callback == nullptr) return;
+
+        std::scoped_lock lock(_mutex);
+        _callback = std::move(callback);
+        _is_loaded = true;
+    }
+
+    void unload() {
+        std::scoped_lock lock(_mutex);
+        _callback = nullptr;
+        _is_loaded = false;
+    }
+
+    bool is_loaded() const { return _is_loaded; }
+
+    explicit operator bool() const { return is_loaded(); }
+
+    _Res operator()(_ArgTypes... arguments) {
+        std::scoped_lock lock(_mutex);
+        if (_is_loaded) {
+            return _callback(std::forward<_ArgTypes&&>(arguments)...);
+        } else {
+            return _Res();
+        }
+    }
+
+  protected:
+    std::atomic_bool _is_loaded{false};
+    std::function<_Res(_ArgTypes...)> _callback;
+    std::recursive_mutex _mutex;
+};
+
+}  // namespace kvn
+
+#endif  // KVN_SAFE_CALLBACK_HPP