4 files changed, 84 insertions, 2 deletions
diff --git a/src/core/file_sys/common_funcs.h b/src/core/file_sys/common_funcs.h
new file mode 100644
index 000000000..7ed97aa50
--- /dev/null
+++ b/src/core/file_sys/common_funcs.h
@@ -0,0 +1,56 @@
+// Copyright 2020 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_types.h"
+
+namespace FileSys {
+
+constexpr u64 AOC_TITLE_ID_MASK = 0x7FF;
+constexpr u64 AOC_TITLE_ID_OFFSET = 0x1000;
+constexpr u64 BASE_TITLE_ID_MASK = 0xFFFFFFFFFFFFE000;
+
+/**
+ * Gets the base title ID from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @returns The base title ID.
+ */
+[[nodiscard]] constexpr u64 GetBaseTitleID(u64 title_id) {
+    return title_id & BASE_TITLE_ID_MASK;
+}
+
+/**
+ * Gets the base title ID with a program index offset from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @param program_index The program index.
+ * @returns The base title ID with a program index offset.
+ */
+[[nodiscard]] constexpr u64 GetBaseTitleIDWithProgramIndex(u64 title_id, u64 program_index) {
+    return GetBaseTitleID(title_id) + program_index;
+}
+
+/**
+ * Gets the AOC (Add-On Content) base title ID from a given title ID.
+ *
+ * @param title_id The title ID.
+ * @returns The AOC base title ID.
+ */
+[[nodiscard]] constexpr u64 GetAOCBaseTitleID(u64 title_id) {
+    return GetBaseTitleID(title_id) + AOC_TITLE_ID_OFFSET;
+}
+
+/**
+ * Gets the AOC (Add-On Content) ID from a given AOC title ID.
+ *
+ * @param aoc_title_id The AOC title ID.
+ * @returns The AOC ID.
+ */
+[[nodiscard]] constexpr u64 GetAOCID(u64 aoc_title_id) {
+    return aoc_title_id & AOC_TITLE_ID_MASK;
+}
+
+} // namespace FileSys
diff --git a/src/core/file_sys/patch_manager.cpp b/src/core/file_sys/patch_manager.cpp
index e9d1607d0..7c3284df8 100644
--- a/src/core/file_sys/patch_manager.cpp
+++ b/src/core/file_sys/patch_manager.cpp
@@ -12,6 +12,7 @@
 #include "common/logging/log.h"
 #include "common/string_util.h"
 #include "core/core.h"
+#include "core/file_sys/common_funcs.h"
 #include "core/file_sys/content_archive.h"
 #include "core/file_sys/control_metadata.h"
 #include "core/file_sys/ips_layer.h"
@@ -30,7 +31,6 @@ namespace FileSys {
 namespace {
 
 constexpr u32 SINGLE_BYTE_MODULUS = 0x100;
-constexpr u64 DLC_BASE_TITLE_ID_MASK = 0xFFFFFFFFFFFFE000;
 
 constexpr std::array<const char*, 14> EXEFS_FILE_NAMES{
     "main",    "main.npdm", "rtld",    "sdk",     "subsdk0", "subsdk1", "subsdk2",
@@ -532,7 +532,7 @@ PatchManager::PatchVersionNames PatchManager::GetPatchVersionNames(VirtualFile u
     dlc_match.reserve(dlc_entries.size());
     std::copy_if(dlc_entries.begin(), dlc_entries.end(), std::back_inserter(dlc_match),
                  [this](const ContentProviderEntry& entry) {
-                     return (entry.title_id & DLC_BASE_TITLE_ID_MASK) == title_id &&
+                     return GetBaseTitleID(entry.title_id) == title_id &&
                             content_provider.GetEntry(entry)->GetStatus() ==
                                 Loader::ResultStatus::Success;
                  });
diff --git a/src/core/file_sys/romfs_factory.cpp b/src/core/file_sys/romfs_factory.cpp
index 987199747..f4e16e4be 100644
--- a/src/core/file_sys/romfs_factory.cpp
+++ b/src/core/file_sys/romfs_factory.cpp
@@ -7,6 +7,7 @@
 #include "common/common_types.h"
 #include "common/logging/log.h"
 #include "core/file_sys/card_image.h"
+#include "core/file_sys/common_funcs.h"
 #include "core/file_sys/content_archive.h"
 #include "core/file_sys/nca_metadata.h"
 #include "core/file_sys/patch_manager.h"
@@ -47,6 +48,27 @@ ResultVal<VirtualFile> RomFSFactory::OpenCurrentProcess(u64 current_process_titl
         patch_manager.PatchRomFS(file, ivfc_offset, ContentRecordType::Program, update_raw));
 }
 
+ResultVal<VirtualFile> RomFSFactory::OpenPatchedRomFS(u64 title_id, ContentRecordType type) const {
+    auto nca = content_provider.GetEntry(title_id, type);
+
+    if (nca == nullptr) {
+        // TODO: Find the right error code to use here
+        return RESULT_UNKNOWN;
+    }
+
+    const PatchManager patch_manager{title_id, filesystem_controller, content_provider};
+
+    return MakeResult<VirtualFile>(
+        patch_manager.PatchRomFS(nca->GetRomFS(), nca->GetBaseIVFCOffset(), type));
+}
+
+ResultVal<VirtualFile> RomFSFactory::OpenPatchedRomFSWithProgramIndex(
+    u64 title_id, u8 program_index, ContentRecordType type) const {
+    const auto res_title_id = GetBaseTitleIDWithProgramIndex(title_id, program_index);
+
+    return OpenPatchedRomFS(res_title_id, type);
+}
+
 ResultVal<VirtualFile> RomFSFactory::Open(u64 title_id, StorageId storage,
                                           ContentRecordType type) const {
     const std::shared_ptr<NCA> res = GetEntry(title_id, storage, type);
diff --git a/src/core/file_sys/romfs_factory.h b/src/core/file_sys/romfs_factory.h
index ec704dfa8..96dd0d578 100644
--- a/src/core/file_sys/romfs_factory.h
+++ b/src/core/file_sys/romfs_factory.h
@@ -42,6 +42,10 @@ public:
 
     void SetPackedUpdate(VirtualFile update_raw);
     [[nodiscard]] ResultVal<VirtualFile> OpenCurrentProcess(u64 current_process_title_id) const;
+    [[nodiscard]] ResultVal<VirtualFile> OpenPatchedRomFS(u64 title_id,
+                                                          ContentRecordType type) const;
+    [[nodiscard]] ResultVal<VirtualFile> OpenPatchedRomFSWithProgramIndex(
+        u64 title_id, u8 program_index, ContentRecordType type) const;
     [[nodiscard]] ResultVal<VirtualFile> Open(u64 title_id, StorageId storage,
                                               ContentRecordType type) const;