1 files changed, 138 insertions, 0 deletions
diff --git a/src/gpg/GpgFunctionObject.h b/src/gpg/GpgFunctionObject.h
new file mode 100644
index 00000000..6f1d60af
--- /dev/null
+++ b/src/gpg/GpgFunctionObject.h
@@ -0,0 +1,138 @@
+/**
+ * This file is part of GpgFrontend.
+ *
+ * GpgFrontend is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Foobar is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Foobar.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * The initial version of the source code is inherited from gpg4usb-team.
+ * Their source code version also complies with GNU General Public License.
+ *
+ * The source code version of this software was modified and released
+ * by Saturneric<[email protected]> starting on May 12, 2021.
+ *
+ */
+
+#ifndef GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H
+#define GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H
+
+#include <easyloggingpp/easylogging++.h>
+
+#include <map>
+#include <memory>
+#include <mutex>
+#include <shared_mutex>
+#include <stdexcept>
+#include <string>
+
+namespace GpgFrontend {
+
+template <typename T>
+class SingletonFunctionObject {
+ public:
+  static T& GetInstance(int channel = 0) {
+    if (!channel) {
+      std::lock_guard<std::mutex> guard(_instance_mutex);
+      if (_instance == nullptr) _instance = std::make_unique<T>();
+      return *_instance;
+    } else {
+      // read _instances_map
+      decltype(_instances_map.end()) _it;
+      {
+        std::shared_lock lock(_instances_mutex);
+        _it = _instances_map.find(channel);
+      }
+      if (_it != _instances_map.end())
+        return *_it->second;
+      else
+        return CreateInstance(channel);
+    }
+  }
+
+  static T& CreateInstance(int channel, std::unique_ptr<T> p_obj = nullptr) {
+    if (!channel) return *_instance;
+
+    // read _instances_map
+    decltype(_instances_map.end()) _it;
+    {
+      std::shared_lock lock(_instances_mutex);
+      _it = _instances_map.find(channel);
+    }
+    if (_it == _instances_map.end()) {
+      {
+        std::lock_guard<std::mutex> guard(_default_channel_mutex);
+        int tmp = channel;
+        std::swap(_default_channel, tmp);
+        if (p_obj == nullptr) p_obj = std::make_unique<T>();
+        std::swap(_default_channel, tmp);
+      }
+      T* obj = p_obj.get();
+
+      // change _instances_map
+      {
+        std::unique_lock lock(_instances_mutex);
+        _instances_map.insert({channel, std::move(p_obj)});
+      }
+      return *obj;
+    } else {
+      return *_it->second;
+    }
+  }
+
+  static int GetDefaultChannel() { return _default_channel; }
+
+  int GetChannel() const { return channel_; }
+
+  SingletonFunctionObject(T&&) = delete;
+
+  SingletonFunctionObject(const T&) = delete;
+
+  void operator=(const T&) = delete;
+
+ protected:
+  SingletonFunctionObject() {}
+
+  SingletonFunctionObject(int channel) : channel_(channel) {}
+
+  virtual ~SingletonFunctionObject() = default;
+
+ private:
+  int channel_ = _default_channel;
+  static int _default_channel;
+  static std::mutex _default_channel_mutex;
+  static std::mutex _instance_mutex;
+  static std::shared_mutex _instances_mutex;
+  static std::unique_ptr<T> _instance;
+  static std::map<int, std::unique_ptr<T>> _instances_map;
+};
+
+template <typename T>
+int SingletonFunctionObject<T>::_default_channel = 0;
+
+template <typename T>
+std::mutex SingletonFunctionObject<T>::_default_channel_mutex;
+
+template <typename T>
+std::mutex SingletonFunctionObject<T>::_instance_mutex;
+
+template <typename T>
+std::shared_mutex SingletonFunctionObject<T>::_instances_mutex;
+
+template <typename T>
+std::unique_ptr<T> SingletonFunctionObject<T>::_instance = nullptr;
+
+template <typename T>
+std::map<int, std::unique_ptr<T>> SingletonFunctionObject<T>::_instances_map;
+
+}  // namespace GpgFrontend
+
+#endif  // GPGFRONTEND_ZH_CN_TS_FUNCTIONOBJECT_H