file_sys: Resolve sign conversion warnings

Resolves a few trivial sign conversion/mismatch errors.

src/core/file_sys/romfs_factory.cpp

@@ -71,12 +71,12 @@ ResultVal<VirtualFile> RomFSFactory::Open(u64 title_id, StorageId storage,
 
     if (res == nullptr) {
         // TODO(DarkLordZach): Find the right error code to use here
-        return ResultCode(-1);
+        return RESULT_UNKNOWN;
     }
     const auto romfs = res->GetRomFS();
     if (romfs == nullptr) {
         // TODO(DarkLordZach): Find the right error code to use here
-        return ResultCode(-1);
+        return RESULT_UNKNOWN;
     }
     return MakeResult<VirtualFile>(romfs);
 }

src/core/file_sys/savedata_factory.cpp

@@ -90,7 +90,7 @@ ResultVal<VirtualDir> SaveDataFactory::Create(SaveDataSpaceId space,
     // Return an error if the save data doesn't actually exist.
     if (out == nullptr) {
         // TODO(DarkLordZach): Find out correct error code.
-        return ResultCode(-1);
+        return RESULT_UNKNOWN;
     }
 
     return MakeResult<VirtualDir>(std::move(out));
@@ -111,7 +111,7 @@ ResultVal<VirtualDir> SaveDataFactory::Open(SaveDataSpaceId space,
     // Return an error if the save data doesn't actually exist.
     if (out == nullptr) {
         // TODO(Subv): Find out correct error code.
-        return ResultCode(-1);
+        return RESULT_UNKNOWN;
     }
 
     return MakeResult<VirtualDir>(std::move(out));

src/core/file_sys/vfs_libzip.cpp

@@ -27,7 +27,7 @@ VirtualDir ExtractZIP(VirtualFile file) {
 
     std::shared_ptr<VectorVfsDirectory> out = std::make_shared<VectorVfsDirectory>();
 
-    const auto num_entries = zip_get_num_entries(zip.get(), 0);
+    const auto num_entries = static_cast<std::size_t>(zip_get_num_entries(zip.get(), 0));
 
     zip_stat_t stat{};
     zip_stat_init(&stat);

src/core/file_sys/xts_archive.cpp

@@ -7,12 +7,13 @@
 #include <cstring>
 #include <regex>
 #include <string>
+
 #include <mbedtls/md.h>
 #include <mbedtls/sha256.h>
-#include "common/assert.h"
+
 #include "common/file_util.h"
 #include "common/hex_util.h"
-#include "common/logging/log.h"
+#include "common/string_util.h"
 #include "core/crypto/aes_util.h"
 #include "core/crypto/xts_encryption_layer.h"
 #include "core/file_sys/partition_filesystem.h"
@@ -53,11 +54,8 @@ NAX::NAX(VirtualFile file_) : header(std::make_unique<NAXHeader>()), file(std::m
         return;
     }
 
-    std::string two_dir = match[1];
-    std::string nca_id = match[2];
-    std::transform(two_dir.begin(), two_dir.end(), two_dir.begin(), ::toupper);
-    std::transform(nca_id.begin(), nca_id.end(), nca_id.begin(), ::tolower);
-
+    const std::string two_dir = Common::ToUpper(match[1]);
+    const std::string nca_id = Common::ToLower(match[2]);
     status = Parse(fmt::format("/registered/{}/{}.nca", two_dir, nca_id));
 }