[Kernel] Added support for writing/reading GPD files

This breaks settings in games that are using them and savefiles in games that use settings to store progress

src/xenia/kernel/xam/user_property.h

@@ -0,0 +1,61 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2024 Xenia Canary. All rights reserved.                          *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef XENIA_KERNEL_XAM_USER_PROPERTY_H_
+#define XENIA_KERNEL_XAM_USER_PROPERTY_H_
+
+#include <variant>
+
+#include "xenia/kernel/xam/user_data.h"
+#include "xenia/memory.h"
+#include "xenia/xbox.h"
+
+namespace xe {
+namespace kernel {
+namespace xam {
+
+// This structure is here because context is a one type of property.
+struct XUSER_CONTEXT {
+  xe::be<uint32_t> context_id;
+  xe::be<uint32_t> value;
+};
+
+struct XUSER_PROPERTY {
+  xe::be<uint32_t> property_id;
+  X_USER_DATA data;
+};
+
+class Property : public UserData {
+ public:
+  Property();
+  Property(const Property& property);
+
+  Property(uint32_t property_id, UserDataTypes setting_data);
+  // Ctor used while guest is creating property.
+  Property(uint32_t property_id, uint32_t value_size, uint8_t* value_ptr);
+  // Ctor used for deserialization
+  Property(const uint8_t* serialized_data, size_t data_size);
+  ~Property();
+
+  const AttributeKey GetPropertyId() const { return property_id_; }
+
+  bool IsValid() const { return property_id_.value != 0; }
+  bool IsContext() const { return data_.type == X_USER_DATA_TYPE::CONTEXT; }
+  void WriteToGuest(XUSER_PROPERTY* property) const;
+  std::vector<uint8_t> Serialize() const;
+
+ private:
+  AttributeKey property_id_ = {};
+};
+
+}  // namespace xam
+}  // namespace kernel
+}  // namespace xe
+
+#endif