Compute checksum for extended SRAM

Validate SRAM on file screen load and delete if checksum incorrect

hooks.asm

@@ -188,7 +188,7 @@ JSL.l AltBufferTable : NOP #8 ; Delete screen
 ;--------------------------------------------------------------------------------
 org $0CCCCC ;<- 64CCC - Bank0C.asm : 1628 (JSL Intro_ValidateSram) / Bank02.asm : 75 (REP #$30)
 ; Explanation: In JP 1.0 the code for Intro_ValidateSram was inline in Bank 0C
-JML.l Validate_SRAM ;(Return via RTL. Original code JML'd to Intro_LoadSpriteStats which returns with RTL, but we want to skip that)
+JML.l ValidateSRAM ;(Return via RTL. Original code JML'd to Intro_LoadSpriteStats which returns with RTL, but we want to skip that)
 org $0CCD57 ;<- 64D57 - Bank0C.asm :
 RTL ;Just in case anybody ever removes the previous hook
 ;--------------------------------------------------------------------------------
@@ -299,12 +299,17 @@ BRA +
 ;================================================================================
 ; Extended SRAM Save file
 ;--------------------------------------------------------------------------------
-org $0ccf08 ; <- Bank0C.asm : 2036 (LDA.w #$0007 : STA $7EC00D : STA $7EC013)
+org $0CCF08 ; <- Bank0C.asm : 2036 (LDA.w #$0007 : STA $7EC00D : STA $7EC013)
 JSL CopyExtendedSaveFileToWRAM
 ;--------------------------------------------------------------------------------
 org $008998 ; <- Bank00.asm : 1296 (LDX.w #$0000)
 JSL CopyExtendedWRAMSaveFileToSRAM
 ;--------------------------------------------------------------------------------
+org $00899C ; <- bank_00.asm : #_00899C (CLC)
+JSL WriteSaveChecksum
+LDA.w #$01F3 : TCS : SEP #$30 : PLB : RTL ; Get the stack and data bank correct
+padbyte $FF : pad $0089C2 ; Fill adjacent free rom forward. See bank_00.asm: #_0089C2
+;--------------------------------------------------------------------------------
 org $0CD7AB ; <- Bank0C.asm : 3342 (STA $700400, X)
 JSL.l ClearExtendedSaveFile
 ;--------------------------------------------------------------------------------
@@ -2807,4 +2812,4 @@ if !FEATURE_NEW_TEXT
         JSL RenderCharSetColorExtended_init
     org $0EF285
         JSL RenderCharSetColorExtended_close : NOP
-endif
+endif

save.asm

@@ -1,12 +1,40 @@
 ;--------------------------------------------------------------------------------
-Validate_SRAM:
+WriteSaveChecksum:
-	REP #$30 ; vanilla behavior from $0CCD45, includes prize pack reset after save and quit
+        LDX.w #$0000 : TXA : - ; Checksum first $04FE bytes
-		LDX #$00FE : -
+                CLC : ADC.l SaveDataWRAM, X
-			STZ $0D00, X
+                INX #2
-			STZ $0E00, X
+        CPX #$04FE : BNE -
-			STZ $0F00, X
+        LDX.w #$0000 : - ; Checksum extended save data
-			DEX #2
+                CLC : ADC.l ExtendedFileNameWRAM, X
-		BPL -
+                INX #2
+        CPX #$0FFE : BNE -
+        STA.b $00
+        LDA.w #$5A5A
+        SEC : SBC.b $00
+        STA.l $7004FE
+RTL
+;--------------------------------------------------------------------------------
+ValidateSRAM:
+        REP #$30
+        LDX.w #$0000 : TXA : - ; Checksum first $04FE bytes
+                CLC : ADC.l CartridgeSRAM,X
+                INX #2
+        CPX.w #$04FE : BNE -
+        LDX.w #$0000 : - ; Checksum extended save data
+                CLC : ADC.l ExtendedFileNameSRAM, X
+                INX #2
+        CPX #$0FFE : BNE -
+        STA.b $00
+        LDA.w #$5A5A
+        SEC : SBC.b $00
+        CMP.l InverseChecksumSRAM : BEQ +
+                TDC : STA.l FileValiditySRAM : + ; Delete save by way of zeroing validity marker
+	LDX.w #$00FE : - ; includes prize pack reset after save and quit
+		STZ $0D00, X
+		STZ $0E00, X
+		STZ $0F00, X
+		DEX #2
+	BPL -
 	SEP #$30
 RTL
 ;--------------------------------------------------------------------------------
@@ -23,6 +51,11 @@ ClearExtendedSaveFile:
 	STA $700D00, X
 	STA $700E00, X
 	STA $700F00, X
+	STA $701000, X
+	STA $701100, X
+	STA $701200, X
+	STA $701300, X
+	STA $701400, X
 RTL
 ;--------------------------------------------------------------------------------
 ClearExtendedWRAMSaveFile:
@@ -125,5 +158,4 @@ CopyExtendedWRAMSaveFileToSRAM:
 	REP #$30
 	PLB
 	PLA
-	LDX.w #$0000 : TXA ; what we wrote over
 RTL

sram.asm

@@ -10,6 +10,7 @@
 ;--------------------------------------------------------------------------------
 pushpc
 org 0 ; This module writes no bytes. Asar gives bank cross errors without this.
+SaveDataWRAM = $7EF000
 
 ;================================================================================
 ; Room Data ($7EF000 - $7EF27F
@@ -366,7 +367,7 @@ GTCollectedKeys: skip 1         ; /  Ganon's Tower
 skip 2                          ; Reserved for previous table
 FileMarker: skip 1              ; $FF = Active save file | $00 = Inactive save file
 skip 13                         ; Unused
-InverseChecksum: skip 2         ; Vanilla Inverse Checksum. Don't write unless computing checksum.
+InverseChecksumWRAM: skip 2     ; Vanilla Inverse Checksum. Don't write unless computing checksum.
 
 ;================================================================================
 ; Expanded SRAM ($7F6000 - $7F6FFF)
@@ -379,8 +380,7 @@ ExtendedFileNameWRAM: skip 24   ; File name, 12 word-length characters.
 RoomPotData: skip 592           ; Table for expanded pot shuffle. One word per room.
 SpritePotData: skip 592         ; Table for expanded pot shuffle. One word per room.
 PurchaseCounts: skip 96         ; Keeps track of shop purchases
-PrivateBlock: skip 512          ; Reserved for 3rd party developers
+PrivateBlock: skip 513          ; Reserved for 3rd party developers
-DummyValue: skip 1              ; $01 if you're a real dummy
 
 ;================================================================================
 ; Direct SRAM Assignments ($700000 - $7080000)
@@ -403,7 +403,8 @@ ProgressIndicatorSRAM: skip 1   ;
 skip 19                         ;
 FileNameVanillaSRAM: skip 8     ; First four characters of file name
 FileValiditySRAM: skip 2        ;
-skip 285                        ;
+skip 283                        ;
+InverseChecksumSRAM: skip 2     ;
 ExtendedFileNameSRAM: skip 24   ; We read and write the file name directly from and to SRAM (24 bytes)
 skip $1AE4                      ;
 RomVersionSRAM: skip 4          ; ALTTPR ROM version. Low byte is the version, high byte writes
@@ -515,7 +516,7 @@ endmacro
 %assertSRAM(FollowerDropped, $7EF3D3)
 %assertSRAM(FileNameVanillaWRAM, $7EF3D9)
 %assertSRAM(FileValidity, $7EF3E1)
-%assertSRAM(InverseChecksum, $7EF4FE)
+%assertSRAM(InverseChecksumWRAM, $7EF4FE)
 
 ;================================================================================
 ; Randomizer Assertions
@@ -640,7 +641,6 @@ endmacro
 %assertSRAM(SpritePotData, $7F6268)
 %assertSRAM(PurchaseCounts, $7F64B8)
 %assertSRAM(PrivateBlock, $7F6518)
-%assertSRAM(DummyValue, $7F6718)
 
 ;================================================================================
 ; Direct SRAM Assertions
@@ -654,6 +654,7 @@ endmacro
 %assertSRAM(ProgressIndicatorSRAM, $7003C5)
 %assertSRAM(FileNameVanillaSRAM, $7003D9)
 %assertSRAM(FileValiditySRAM, $7003E1)
+%assertSRAM(InverseChecksumSRAM, $7004FE)
 %assertSRAM(ExtendedFileNameSRAM, $700500)
 %assertSRAM(RomNameSRAM, $702000)
 %assertSRAM(RomVersionSRAM, $701FFC)