Treat empty MKW save as missing rather than corrupt (#168)

* treat empty mkw save as missing

first-run format zero-fills rksys.dat before any real save; a quit before
the first save left an all-zero file that read back as corrupt and trapped
the user in a delete/recreate loop. read opens now treat an all-zero
rksys.dat as absent (a real save always begins with the RKSD0006 header),
so the game recreates it from scratch. also ignore native build output.

* shorten

* I dont really want to change this to be honest.

* extra safety

---------

Co-authored-by: patchzyy <64382339+patchzyy@users.noreply.github.com>

runtime/src/hle/storage/nand_api.cpp

@@ -93,6 +93,9 @@ extern "C" int32_t NANDOpen_HLE(uint32_t pathPtr, uint32_t fileInfoPtr, uint32_t
 
     const std::filesystem::path hostPath = TranslateNandPath(path);
 
+    if (const auto result = NandCheckSystemSaveRead("NANDOpen", hostPath, mode))
+        return *result;
+
     // Existing-file write opens go through a shadow copy seeded from the original, so a
     // crash between NANDWrite and NANDClose cannot leave a torn file (the game patches
     // sub-ranges, e.g. ghost saves at a non-zero offset). New files still create in place.

runtime/src/hle/storage/nand_async.cpp

@@ -411,6 +411,8 @@ extern "C" int32_t NANDSafeOpen_HLE(uint32_t pathPtr, uint32_t fileInfoPtr, uint
     if (mode == 1) {
         // Read-only safe open reads the original in place; the library builds no scratch
         // copy for this case.
+        if (const auto result = NandCheckSystemSaveRead("NANDSafeOpen", hostPath, mode))
+            return *result;
         FILE* file = NandFopen(hostPath, "rb");
         if (!file && IsFaceLibResourcePath(path) && SeedFaceLibResource(hostPath)) {
             file = NandFopen(hostPath, "rb");

runtime/src/hle/storage/nand_fs.cpp

@@ -411,6 +411,26 @@ bool IsFaceLibResourcePath(const char* path) {
     return std::strcmp(path, "/shared2/menu/FaceLib/RFL_Res.dat") == 0;
 }
 
+std::optional<int32_t> NandCheckSystemSaveRead(const char* who,
+    const std::filesystem::path& hostPath, int mode, bool ios) {
+    const auto action = RuntimeNandSave::CheckRead(hostPath, mode);
+    if (action == RuntimeNandSave::ReadAction::Proceed) return std::nullopt;
+    if (action == RuntimeNandSave::ReadAction::Missing) {
+        LogNandWarning(who, "treating empty or zero-filled system save '%s' as missing",
+                       HostPathText(hostPath).c_str());
+        return ios ? ISFS_ENOENT : NAND_RESULT_NOEXISTS;
+    }
+    if (action == RuntimeNandSave::ReadAction::RecoveryNeeded) {
+        LogNandError(who, "system save '%s' is missing or blank but its .nandsafe.tmp contains data; "
+                         "back up both files before attempting recovery",
+                     HostPathText(hostPath).c_str());
+    } else {
+        LogNandError(who, "could not inspect system save '%s' or its write shadow; leaving data untouched",
+                     HostPathText(hostPath).c_str());
+    }
+    return ios ? ISFS_EIO : NAND_RESULT_UNKNOWN;
+}
+
 // Create directories recursively
 bool CreateDirectoryPath(const std::filesystem::path& path) {
     if (path.empty()) {

runtime/src/hle/storage/nand_internal.h

@@ -9,6 +9,7 @@
 #include "hle/runtime_parse_helpers.h"
 #include "memory.h"
 #include "nand_path.h"
+#include "nand_save_probe.h"
 #include "hle/net/network.h"
 #include "recomp_mod_loader.h"
 #include "runtime_config.h"
@@ -26,6 +27,7 @@
 #include <deque>
 #include <map>
 #include <mutex>
+#include <optional>
 #include <vector>
 #include <filesystem>
 #include <string>
@@ -56,6 +58,11 @@ constexpr uint32_t kNandTitleIdLo = 0x524D4350; // "RMCP" fallback
 void LogNandError(const char* func, const char* fmt, ...);
 void LogNandWarning(const char* func, const char* fmt, ...);
 
+// An empty optional means continue opening normally; otherwise return the
+// supplied NAND/IOS error without exposing a failed scan as a missing save.
+std::optional<int32_t> NandCheckSystemSaveRead(const char* who,
+    const std::filesystem::path& hostPath, int mode, bool ios = false);
+
 // ============================================================================
 // File Descriptor Management
 // ============================================================================

runtime/src/hle/storage/nand_isfs.cpp

@@ -391,6 +391,9 @@ extern "C" int32_t NAND_IOS_Open_HLE(uint32_t pathPtr, uint32_t mode) {
     
     // It's a NAND file path
     const std::filesystem::path hostPath = TranslateNandPath(path);
+
+    if (const auto result = NandCheckSystemSaveRead("IOS_Open", hostPath, mode, true))
+        return *result;
     
     // Seed FaceLib resources before the existence check so every open mode can
     // still find them on a fresh managed NAND.