libretro: Expose main RAM to frontend

src/duckstation-libretro/libretro_host_interface.cpp

@@ -5,6 +5,7 @@
 #include "common/log.h"
 #include "common/string_util.h"
 #include "core/analog_controller.h"
+#include "core/bus.h"
 #include "core/digital_controller.h"
 #include "core/game_list.h"
 #include "core/gpu.h"
@@ -299,6 +300,30 @@ bool LibretroHostInterface::retro_unserialize(const void* data, size_t size)
   return true;
 }
 
+void* LibretroHostInterface::retro_get_memory_data(unsigned id)
+{
+  switch (id)
+  {
+    case RETRO_MEMORY_SYSTEM_RAM:
+      return m_system ? m_system->GetBus()->GetRAM() : nullptr;
+
+    default:
+      return nullptr;
+  }
+}
+
+size_t LibretroHostInterface::retro_get_memory_size(unsigned id)
+{
+  switch (id)
+  {
+    case RETRO_MEMORY_SYSTEM_RAM:
+      return Bus::RAM_SIZE;
+
+    default:
+      return 0;
+  }
+}
+
 bool LibretroHostInterface::AcquireHostDisplay()
 {
   // start in software mode, switch to hardware later

src/duckstation-libretro/libretro_host_interface.h

@@ -37,6 +37,8 @@ public:
   size_t retro_serialize_size();
   bool retro_serialize(void* data, size_t size);
   bool retro_unserialize(const void* data, size_t size);
+  void* retro_get_memory_data(unsigned id);
+  size_t retro_get_memory_size(unsigned id);
 
 protected:
   bool AcquireHostDisplay() override;

src/duckstation-libretro/main.cpp

@@ -111,12 +111,12 @@ RETRO_API unsigned retro_get_region(void)
 
 RETRO_API void* retro_get_memory_data(unsigned id)
 {
-  return nullptr;
+  return g_libretro_host_interface.retro_get_memory_data(id);
 }
 
 RETRO_API size_t retro_get_memory_size(unsigned id)
 {
-  return 0;
+  return g_libretro_host_interface.retro_get_memory_size(id);
 }
 
 RETRO_API void retro_set_environment(retro_environment_t f)