Misc: Make struct member functions file-local

src/util/cd_image_memory.cpp

@@ -1,16 +1,21 @@
-// SPDX-FileCopyrightText: 2019-2022 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
 // SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
 
 #include "cd_image.h"
 #include "cd_subchannel_replacement.h"
+
 #include "common/assert.h"
 #include "common/file_system.h"
 #include "common/log.h"
 #include "common/path.h"
+
 #include <algorithm>
 #include <cerrno>
+
 Log_SetChannel(CDImageMemory);
 
+namespace {
+
 class CDImageMemory : public CDImage
 {
 public:
@@ -33,6 +38,8 @@ private:
   CDSubChannelReplacement m_sbi;
 };
 
+} // namespace
+
 CDImageMemory::CDImageMemory() = default;
 
 CDImageMemory::~CDImageMemory()