BeyondDarkCastleTuneup: Add magtapes to BDC Prefs

Patch the new-saved-game code to route newly added 'MagT' resources into
BDC Prefs, which is user-modifiable, instead of BDC Data B, which isn't.

Author: jjuran

mac/hacks/BeyondDarkCastleTuneup/BeyondDarkCastleTuneup.cc

@@ -16,6 +16,8 @@
 
 #define IDENTIFYING_RESTYPE  'GDSK'
 
+#define SAVEGAME_CODE_RESID  12
+
 #define ENVCHECK_CODE_RESID  4
 #define SPINLOOP_CODE_RESID  3
 

mac/hacks/CastleTuneup-template/CastleTuneup.cc.hh

@@ -11,7 +11,48 @@
 	This is a set of application hot patches for Dark Castle
 	and Beyond Dark Castle.  The two games share a great deal
 	of code (with similar sets of compatibility issues with
-	Advanced Mac Substitute), but in different locations.
+	Advanced Mac Substitute), though in different locations.
+	
+	Beyond Dark Castle also introduces new logic that's not
+	present in Dark Castle, to support its new features like
+	saved games.  This is the subject of our first patch.
+	
+	Beyond Dark Castle shipped on two 800K disks.  The second
+	disk is required for all gameplay.  In order to support
+	single-drive systems, Beyond Dark Castle was designed to
+	require only the second disk until gameplay ended.  The
+	BDC Data B file contains 'CODE' and other resources for
+	this purpose, and the saved game resources (type 'MagT')
+	are added to BDC Data B, not BDC Prefs (on disk one).
+	
+	Advanced Mac Substitute maintains a distinction between
+	application files and user files.  The Castle Prefs INITs
+	already address the problem of Castle Prefs (and BDC Prefs)
+	being load-bearing game files (that must exist and aren't
+	created by the game) by copying them to the Preferences
+	folder if they don't already exist there.  Clearly, saved
+	games should also be stored in the user's BDC Prefs file.
+	
+	Normally we'd patch the relevant 'CODE' resource in our
+	startup patch (of _TEInit), but here, we can't do that --
+	the code to be patched lives in BDC Data B, which isn't
+	opened until gameplay starts.  Instead, we'll patch one
+	of the Toolbox routines, _CurResFile.  The game-saving
+	logic uses the usual Cur/Use/Add/Use pattern to add the
+	resource to a specific resource file.  Presumably, this
+	was originally intended to be the prefs file but had to
+	be changed to the Data B file to avoid requiring disk
+	switches.  In our _CurResFile patch, we try to load the
+	'CODE' id=12 resource.  If we're post-game saving a high
+	score, BDC Data B will be closed and the load will fail.
+	But if we're in-game saving the game state, the load is
+	guaranteed to succeed (because the very same resource is
+	the one currently executing).  All we need to do here is
+	to substitute the BDC Prefs refnum for the Data B refnum.
+	
+	Since we're patching _CurResFile in the application (and
+	not at system startup time), we have to remove the patch
+	as well, so we patch _ExitToShell and remove both there.
 	
 	The subsequent comments refer to "Dark Castle", but apply
 	equally to both Dark Castle and Beyond Dark Castle.
@@ -56,9 +97,90 @@
 #include "mac_sys/trap_address.hh"
 
 
+enum
+{
+	_CurResFile  = 0xA994,
+	_ExitToShell = 0xA9F4,
+	_TEInit      = 0xA9CC,
+};
+
+static UniversalProcPtr old_CurResFile;
+static UniversalProcPtr old_ExitToShell;
 static UniversalProcPtr old_TEInit;
 
 
+static
+void CurResFile_handler()
+{
+	using mac::glue::GetHandleSize_raw;
+	
+	enum
+	{
+		// These are offsets relative to the start of the 'CODE' resource.
+		
+		offset_to_CurResFile = 0x02d0,
+		offset_to_MOVE_pop   = 0x02d2,  // MOVE.W  (A7)+,D6
+		offset_to_MOVE_push  = 0x02d4,  // MOVE.W  (-746,A5),-(A7)
+		offset_to_A5_index   = offset_to_MOVE_push + 2,
+		offset_to_UseResFile = offset_to_A5_index + 2,
+		minimum_handle_size  = offset_to_UseResFile + 2,
+	};
+	
+	enum
+	{
+		A5_index_of_DataB_refnum = (UInt16) -746,
+		A5_index_of_Prefs_refnum = (UInt16) -744,
+	};
+	
+	if ( Handle h = GetResource( 'CODE', SAVEGAME_CODE_RESID ) )
+	{
+		Size size = GetHandleSize_raw( h );
+		
+		if ( size >= minimum_handle_size )
+		{
+			UInt16* p = (UInt16*) (*h + offset_to_CurResFile);
+			
+			if ( *p++ == _CurResFile  &&
+			     *p++ == 0x3C1F       &&
+			     *p++ == 0x3F2D       &&
+			     *p   == A5_index_of_DataB_refnum )
+			{
+				*p = A5_index_of_Prefs_refnum;
+			}
+		}
+	}
+}
+
+static
+asm
+pascal short CurResFile_patch()
+{
+	LINK     A6,#0
+	MOVEM.L  D1-D2/A1,-(SP)
+	
+	JSR      CurResFile_handler
+	
+	MOVEM.L  (SP)+,D1-D2/A1
+	UNLK     A6
+	
+	MOVEA.L  old_CurResFile,A0
+	JMP      (A0)
+}
+
+static
+void ExitToShell_patch()
+{
+	using mac::sys::set_trap_address;
+	
+	set_trap_address( old_CurResFile,  _CurResFile  );
+	set_trap_address( old_ExitToShell, _ExitToShell );
+	
+	asm
+	{
+		DC.W     _ExitToShell | 0x400  // autoPop
+	}
+}
+
 static inline
 void install_envcheck_patch( Handle h, Size handle_size )
 {
@@ -129,10 +251,23 @@ void TEInit_handler()
 {
 	using mac::glue::GetHandleSize_raw;
 
+	using mac::sys::get_trap_address;
+	using mac::sys::set_trap_address;
+	
 	if ( Handle h = GetResource( IDENTIFYING_RESTYPE, 0 ) )
 	{
 		ReleaseResource( h );
 
+	#ifdef SAVEGAME_CODE_RESID
+		
+		old_CurResFile  = get_trap_address( _CurResFile  );
+		old_ExitToShell = get_trap_address( _ExitToShell );
+		
+		set_trap_address( (ProcPtr) CurResFile_patch,  _CurResFile  );
+		set_trap_address( (ProcPtr) ExitToShell_patch, _ExitToShell );
+		
+	#endif
+		
 		if ( (h = GetResource( 'CODE', ENVCHECK_CODE_RESID )) )
 		{
 			install_envcheck_patch( h, GetHandleSize_raw( h ) );
@@ -158,11 +293,6 @@ pascal asm void TEInit_patch()
 
 int main()
 {
-	enum
-	{
-		_TEInit = 0xA9CC,
-	};
-	
 	Handle self = GetResource( 'INIT', 0 );
 
 	DetachResource( self );