From 4c67e48456a9071ddce569fc49b503b0ecf86a12 Mon Sep 17 00:00:00 2001
From: Gregory Heskett <gheskett@gmail.com>
Date: Mon, 6 Mar 2023 20:53:08 -0500
Subject: [PATCH] Add define for wiping save data if existing save data from
 vanilla or another hack exists (#579)

---
 include/config/config_rom.h |  7 +++++++
 src/game/save_file.c        | 23 +++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/config/config_rom.h b/include/config/config_rom.h
index 76e664a98..a5927c3d6 100644
--- a/include/config/config_rom.h
+++ b/include/config/config_rom.h
@@ -29,6 +29,13 @@
 #define BORDER_HEIGHT_CONSOLE  0
 #define BORDER_HEIGHT_EMULATOR 0
 
+/**
+ * Force the game to delete any existing save data originating from a different hack. This requires INTERNAL_ROM_NAME to be unique to work properly.
+ * It is recommended to enable this if any significant changes to the save file are made that could cause issues with this or other hacks.
+ * NOTE: Using save editors with this define will likely just end up wiping your save, since SM64 specific save editors most likely use hardcoded save magic.
+ */
+// #define UNIQUE_SAVE_DATA
+
 /**
  * Informs supported emulators to default to gamecube controller inputs.
  */
diff --git a/src/game/save_file.c b/src/game/save_file.c
index 4663adac8..1e95415f4 100644
--- a/src/game/save_file.c
+++ b/src/game/save_file.c
@@ -18,8 +18,13 @@
 #endif
 #include "puppycam2.h"
 
+#ifdef UNIQUE_SAVE_DATA
+u16 MENU_DATA_MAGIC = 0x4849;
+u16 SAVE_FILE_MAGIC = 0x4441;
+#else
 #define MENU_DATA_MAGIC 0x4849
 #define SAVE_FILE_MAGIC 0x4441
+#endif
 
 //STATIC_ASSERT(sizeof(struct SaveBuffer) == EEPROM_SIZE, "eeprom buffer size must match");
 
@@ -332,10 +337,28 @@ void save_file_copy(s32 srcFileIndex, s32 destFileIndex) {
     save_file_do_save(destFileIndex);
 }
 
+#ifdef UNIQUE_SAVE_DATA
+// This should only be called once on boot and never again.
+static void calculate_unique_save_magic(void) {
+    u16 checksum = 0;
+
+    for (s32 i = 0; i < 20; i++) {
+        checksum += (u16) INTERNAL_ROM_NAME[i] << (i & 0x07);
+    }
+
+    MENU_DATA_MAGIC += checksum;
+    SAVE_FILE_MAGIC += checksum;
+}
+#endif
+
 void save_file_load_all(void) {
     s32 file;
     s32 validSlots;
 
+#ifdef UNIQUE_SAVE_DATA
+    calculate_unique_save_magic(); // This should only be called once on boot and never again.
+#endif
+
     gMainMenuDataModified = FALSE;
     gSaveFileModified = FALSE;