System: Use existing CD media when loading state where possible

src/core/cdrom.cpp

@@ -450,15 +450,15 @@ void CDROM::InsertMedia(std::unique_ptr<CDImage> media)
   m_reader.SetMedia(std::move(media));
 }
 
-void CDROM::RemoveMedia(bool force /* = false */)
+std::unique_ptr<CDImage> CDROM::RemoveMedia(bool force /* = false */)
 {
   if (!HasMedia() && !force)
-    return;
+    return nullptr;
 
   const TickCount stop_ticks = GetTicksForStop(true);
 
   Log_InfoPrintf("Removing CD...");
-  m_reader.RemoveMedia();
+  std::unique_ptr<CDImage> image = m_reader.RemoveMedia();
 
   m_last_sector_header_valid = false;
 
@@ -484,6 +484,8 @@ void CDROM::RemoveMedia(bool force /* = false */)
     m_drive_state = DriveState::ShellOpening;
     m_drive_event->SetIntervalAndSchedule(stop_ticks);
   }
+
+  return image;
 }
 
 void CDROM::SetUseReadThread(bool enabled)

src/core/cdrom.h

@@ -32,7 +32,7 @@ public:
   std::string GetMediaFileName() const { return m_reader.GetMediaFileName(); }
 
   void InsertMedia(std::unique_ptr<CDImage> media);
-  void RemoveMedia(bool force = false);
+  std::unique_ptr<CDImage> RemoveMedia(bool force = false);
 
   // I/O
   u8 ReadRegister(u32 offset);

src/core/cdrom_async_reader.cpp

@@ -43,10 +43,10 @@ void CDROMAsyncReader::SetMedia(std::unique_ptr<CDImage> media)
   m_media = std::move(media);
 }
 
-void CDROMAsyncReader::RemoveMedia()
+std::unique_ptr<CDImage> CDROMAsyncReader::RemoveMedia()
 {
   WaitForReadToComplete();
-  m_media.reset();
+  return std::move(m_media);
 }
 
 void CDROMAsyncReader::QueueReadSector(CDImage::LBA lba)

src/core/cdrom_async_reader.h

@@ -26,7 +26,7 @@ public:
   void StopThread();
 
   void SetMedia(std::unique_ptr<CDImage> media);
-  void RemoveMedia();
+  std::unique_ptr<CDImage> RemoveMedia();
 
   void QueueReadSector(CDImage::LBA lba);
   void QueueReadNextSector();

src/core/system.cpp

@@ -432,11 +432,17 @@ bool System::DoLoadState(ByteStream* state, bool init_components, bool force_sof
       return false;
     }
 
-    media = CDImage::Open(media_filename.c_str());
-    if (!media)
+    media = m_cdrom->RemoveMedia();
+    if (!media || media->GetFileName() != media_filename)
     {
-      m_host_interface->ReportFormattedError("Failed to open CD image from save state: '%s'.", media_filename.c_str());
-      return false;
+      media.reset();
+      media = CDImage::Open(media_filename.c_str());
+      if (!media)
+      {
+        m_host_interface->ReportFormattedError("Failed to open CD image from save state: '%s'.",
+                                               media_filename.c_str());
+        return false;
+      }
     }
   }