PSP: save through the real sceUtilitySavedata API, not raw file I/O

Rewrote savepsp.c/savestreampsp.c to use sceUtilitySavedataInitStart/
Update/GetStatus/ShutdownStart instead of sceIoOpen/Read/Write, so PSP
saves get a proper OS-generated PARAM.SFO (title/savedataTitle/detail) and
show up correctly in the native save browser.

This dialog spans multiple frames and, per this project's prior experience
with the network config dialog, must be pumped non-blocking one step per
real engine frame rather than blocked on synchronously - a raw-sceGu
blocking loop already froze the app on real hardware for that dialog,
since pspGL owns the GU context. So save.h's saveWrite()/saveLoad() are
now callback-based (savecallback_t onComplete) instead of returning a
result directly, mirroring networkRequestConnection()'s shape, with a new
saveUpdate() (wired into engineUpdate()) pumping the active op each frame.
Linux/Dolphin behavior is unchanged - their fallback path in save.c still
completes synchronously, just via an immediate callback call instead of a
direct return.

Two real bugs found via PPSSPP testing (not just code review): SAVE/LOAD
modes show a confirm screen even for brand-new data, which blocks forever
headlessly - switched to AUTOSAVE/AUTOLOAD, which write/read silently and
generate the identical PARAM.SFO. And PPSSPP's dialog status goes straight
from QUIT to NONE without a separately observable FINISHED in between,
which the first version misread as "disappeared without a result" even on
a successful save - fixed by tracking whether QUIT was already seen.

Confirmed end-to-end in PPSSPP: write, dialog completes, PARAM.SFO +
encrypted save.bin appear on the virtual memory stick, and a subsequent
load decrypts/deserializes back to the exact original data. Not tested on
real PSP hardware.

src/duskpsp/save/savepsp.h

@@ -9,29 +9,50 @@
 #include "error/error.h"
 #include "save/savefile.h"
 #include <pspiofilemgr.h>
+#include <psputility.h>
 
 #define SAVE_PSP_PATH_MAX 256
 #define SAVE_PSP_ROOT "ms0:/"
-#define SAVE_PSP_BASE_DIR "ms0:/PSP"
-#define SAVE_PSP_SAVEDATA_DIR "ms0:/PSP/SAVEDATA"
-#define SAVE_PSP_FILE_FORMAT "ms0:/PSP/SAVEDATA/%s%02u/save.dat"
-#define SAVE_PSP_DIR_FORMAT "ms0:/PSP/SAVEDATA/%s%02u"
+#define SAVE_PSP_FILE_NAME "save.bin"
+#define SAVE_PSP_FILE_FORMAT "ms0:/PSP/SAVEDATA/%s%02u/" SAVE_PSP_FILE_NAME
+#define SAVE_PSP_DATA_BUFFER_SIZE 4096
 
-#ifndef SAVE_PSP_TITLE_ID
-  #define SAVE_PSP_TITLE_ID "DUSK00001"
+#ifndef SAVE_PSP_GAME_NAME
+  #define SAVE_PSP_GAME_NAME "DUSK00001"
 #endif
 
+typedef enum {
+  SAVE_PSP_OP_NONE,
+  SAVE_PSP_OP_SAVE,
+  SAVE_PSP_OP_LOAD
+} savepspop_t;
+
 typedef struct {
-  uint8_t unused;
+  SceUtilitySavedataParam param;
+  // Raw buffer sceUtilitySavedata reads/writes the whole save into/from -
+  // populated by our own savestream_t serialization (see savestreampsp.h)
+  // before a save starts, and deserialized from after a load finishes.
+  uint8_t dataBuffer[SAVE_PSP_DATA_BUFFER_SIZE] __attribute__((aligned(64)));
+  size_t dataLength;
+
+  savepspop_t op;
+  // True once sceUtilitySavedataShutdownStart() has been requested (dialog
+  // status PSP_UTILITY_DIALOG_QUIT seen) - distinguishes a normal "torn
+  // down after finishing" NONE/FINISHED from a genuinely unexpected one
+  // seen before ever reaching QUIT. Some implementations (confirmed on
+  // PPSSPP) settle straight to NONE after shutdown without a separately
+  // observable FINISHED step in between.
+  bool_t shuttingDown;
+  uint8_t slot;
+  savecallback_t onComplete;
+  void *onCompleteUser;
 } savepsp_t;
 
 /**
  * Initializes the save system on PSP. Confirms the memory stick is
  * actually reachable (sceIoGetstat on SAVE_PSP_ROOT) rather than assuming
- * so, since raw sceIo calls otherwise only fail once something tries to
- * touch the filesystem - and ensures the PSP/SAVEDATA directory tree
- * exists (SAVE_PSP_BASE_DIR then SAVE_PSP_SAVEDATA_DIR, since sceIoMkdir
- * only creates one level at a time).
+ * so, since the savedata dialog otherwise only reports failure once a
+ * save/load is actually attempted.
  *
  * @return An error code if no memory stick is reachable.
  */
@@ -45,25 +66,7 @@ errorret_t saveInitPSP(void);
 errorret_t saveDisposePSP(void);
 
 /**
- * Loads a save file from PSP save data for the given slot.
- *
- * @param slot The save slot index.
- * @param file Output save file data.
- * @return An error code if the load fails.
- */
-errorret_t saveLoadPSP(const uint8_t slot, savefile_t *file);
-
-/**
- * Writes a save file to PSP save data for the given slot.
- *
- * @param slot The save slot index.
- * @param file Save file data to write.
- * @return An error code if the write fails.
- */
-errorret_t saveWritePSP(const uint8_t slot, const savefile_t *file);
-
-/**
- * Deletes the save file for the given slot from PSP save data.
+ * Deletes the save data folder for the given slot from the memory stick.
  *
  * @param slot The save slot index.
  * @return An error code if the delete fails.
@@ -71,10 +74,54 @@ errorret_t saveWritePSP(const uint8_t slot, const savefile_t *file);
 errorret_t saveDeletePSP(const uint8_t slot);
 
 /**
- * Ensures SAVE_PSP_BASE_DIR and SAVE_PSP_SAVEDATA_DIR both exist, creating
- * whichever are missing. sceIoMkdir only creates one directory level at a
- * time, so this must run before creating any per-slot save directory
- * beneath SAVE_PSP_SAVEDATA_DIR. Safe to call repeatedly - an
- * already-exists result is not an error.
+ * Starts a save via the native sceUtilitySavedata dialog (mode AUTOSAVE -
+ * writes silently with just a brief icon flash, no confirm screen, since
+ * SAVE mode shows one even for a slot with no existing data - but
+ * PARAM.SFO/title/description are generated identically regardless of
+ * mode, and the OS handles the save browser entry either way) for the
+ * given slot. Serializes SAVE.files[slot] into SAVE.platform.dataBuffer
+ * first, synchronously, then kicks off the dialog and returns - completion
+ * is reported later via onComplete, driven by savePSPUpdate() each frame.
+ * If no save data exists yet for this slot, sceUtilitySavedataInitStart()
+ * creates it.
+ *
+ * @param slot The save slot index.
+ * @param onComplete Callback invoked once the dialog finishes.
+ * @param user User data passed through to onComplete.
  */
-void savePSPEnsureBaseDirs(void);
+void savePSPBeginSave(
+  const uint8_t slot, savecallback_t onComplete, void *user
+);
+
+/**
+ * Starts a load via the native sceUtilitySavedata dialog (mode AUTOLOAD -
+ * see savePSPBeginSave() for why not the plain LOAD mode) for the given
+ * slot, unless a quick sceIoGetstat check finds no save data for this slot
+ * yet - in which case onComplete is invoked immediately with
+ * SAVE.files[slot].exists left false, matching the other platforms'
+ * "no file yet" semantics, and no dialog is shown at all.
+ *
+ * @param slot The save slot index.
+ * @param onComplete Callback invoked once the dialog (or immediate
+ *   not-found short-circuit) finishes.
+ * @param user User data passed through to onComplete.
+ */
+void savePSPBeginLoad(
+  const uint8_t slot, savecallback_t onComplete, void *user
+);
+
+/**
+ * Pumps the in-progress save/load dialog one step, if any - must be called
+ * every engine frame (see saveUpdate()). No-op if no dialog is active.
+ *
+ * @return An error code indicating success or failure.
+ */
+errorret_t savePSPUpdate(void);
+
+/**
+ * True while a save/load dialog is in progress (see savePSPBeginSave()/
+ * savePSPBeginLoad()).
+ *
+ * @return True if a save/load dialog is currently open.
+ */
+bool_t savePSPIsBusy(void);