Added compatibility checking when loading a save game - based on hashing the global structure offset tables.

Platform/Apple/virtual/src/plasma/diskops.pla

@@ -232,13 +232,11 @@ def loadInternal()
     guaranteeMLI(MLI_CLOSE, @close_params)
   fin
 
-  // Init the heap with the correct size
+  // Copy the heap up, and init it with the correct size.
   p_loaded = $4000
+  copyHeap(1)  // main to aux
   initHeap(p_loaded=>w_heapSize)
   global = getGlobals()
-
-  // Now copy the data back up to the heap space, and we're done
-  copyHeap(1)  // main to aux
   return TRUE
 end
 

Platform/Apple/virtual/src/plasma/gameloop.pla

@@ -450,33 +450,27 @@ asm getXReg
 end
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
-// Calculate 16-bit hash of a string
-asm hashString
-  +asmPlasm 1
+// Calculate 16-bit hash of a buffer. arg1=pointer, arg2=length
+export asm hashBuffer
+  +asmPlasm 2
+  lda evalStkL+1,x  ; first arg is buffer pointer
   sta pTmp
-  sty pTmp+1
+  lda evalStkH+1,x
+  sta pTmp+1
+  lda evalStkL,x    ; second arg is length
+  tax
   ldy #0
   sty tmp+1
-  lda (pTmp),y
-  tax
+  tya
+  clc
+- adc (pTmp),y
+  ror
+  ror tmp+1
+  ror
+  ror tmp+1
+  ror
+  ror tmp+1
   iny
-- clc
-  adc (pTmp),y
-  bcc +
-  inc tmp+1
-+ asl
-  rol tmp+1
-  bcc +
-  ora #1
-+ asl
-  rol tmp+1
-  bcc +
-  ora #1
-+ asl
-  rol tmp+1
-  bcc +
-  ora #1
-+ iny
   dex
   bne -
   ldy tmp+1
@@ -1575,6 +1569,11 @@ def kbdLoop()
   loop
 end
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+def hashString(str)
+  return hashBuffer(str+1, ^str)
+end
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 export def showMapName(mapName)
   word newNameHash
@@ -2259,6 +2258,7 @@ end
 // Set up the small-object heap. Set loadedSize to zero on initial, or non-zero for loaded game.
 export def initHeap(loadedSize)
   byte i
+  word typeHash
 
   if !heapLocked
     mmgr(SET_MEM_TARGET, HEAP_BOTTOM)
@@ -2276,10 +2276,15 @@ export def initHeap(loadedSize)
     mmgr(HEAP_ADD_TYPE, typeTbls[i])
     i = i+1
   loop
+  typeHash = hashBuffer(@typeTbl_Global, @typeTbls - @typeTbl_Global)
   if loadedSize <> 0
     global = HEAP_BOTTOM
+    if global=>w_typeHash <> typeHash
+      fatal("Incompatible saved game")
+    fin
   else
     global = mmgr(HEAP_ALLOC, TYPE_GLOBAL)
+    global=>w_typeHash = typeHash
   fin
 end
 

Platform/Apple/virtual/src/plasma/playtype.plh

@@ -30,8 +30,9 @@ struc Global
   // Shared player gold amount
   word w_gold
 
-  // Heap size for restoring saved game
+  // Heap size for restoring saved game, and hash of type table to check compatibility of old saves.
   word w_heapSize
+  word w_typeHash
 
   // General flags maintained by scripts. Linked list of Modifiers.
   word p_gameFlags