From 8f183a47dd3dca5247b893960afd09b6f603ae87 Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Thu, 1 Nov 2018 20:24:32 -0400
Subject: [PATCH] filesystem: Cache RegisteredCacheUnion instead of
 constructing on demand Prevents unnecessary re-reads of the metadata and
 unnecessary temporary objects.

---
 src/core/hle/service/filesystem/filesystem.cpp | 13 ++++++++++---
 src/core/hle/service/filesystem/filesystem.h   |  2 +-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/core/hle/service/filesystem/filesystem.cpp b/src/core/hle/service/filesystem/filesystem.cpp
index e32a7c48e..ad865751f 100644
--- a/src/core/hle/service/filesystem/filesystem.cpp
+++ b/src/core/hle/service/filesystem/filesystem.cpp
@@ -319,9 +319,16 @@ ResultVal<FileSys::VirtualDir> OpenSDMC() {
     return sdmc_factory->Open();
 }
 
-std::unique_ptr<FileSys::RegisteredCacheUnion> GetUnionContents() {
-    return std::make_unique<FileSys::RegisteredCacheUnion>(std::vector<FileSys::RegisteredCache*>{
-        GetSystemNANDContents(), GetUserNANDContents(), GetSDMCContents()});
+std::shared_ptr<FileSys::RegisteredCacheUnion> registered_cache_union;
+
+std::shared_ptr<FileSys::RegisteredCacheUnion> GetUnionContents() {
+    if (registered_cache_union == nullptr) {
+        registered_cache_union =
+            std::make_shared<FileSys::RegisteredCacheUnion>(std::vector<FileSys::RegisteredCache*>{
+                GetSystemNANDContents(), GetUserNANDContents(), GetSDMCContents()});
+    }
+
+    return registered_cache_union;
 }
 
 FileSys::RegisteredCache* GetSystemNANDContents() {
diff --git a/src/core/hle/service/filesystem/filesystem.h b/src/core/hle/service/filesystem/filesystem.h
index 6ca5c5636..6f3e0cd03 100644
--- a/src/core/hle/service/filesystem/filesystem.h
+++ b/src/core/hle/service/filesystem/filesystem.h
@@ -47,7 +47,7 @@ ResultVal<FileSys::VirtualDir> OpenSaveData(FileSys::SaveDataSpaceId space,
                                             FileSys::SaveDataDescriptor save_struct);
 ResultVal<FileSys::VirtualDir> OpenSDMC();
 
-std::unique_ptr<FileSys::RegisteredCacheUnion> GetUnionContents();
+std::shared_ptr<FileSys::RegisteredCacheUnion> GetUnionContents();
 
 FileSys::RegisteredCache* GetSystemNANDContents();
 FileSys::RegisteredCache* GetUserNANDContents();