more work on string support

src/basic/engine/varstr_free.s

@@ -6,14 +6,11 @@
 // Releases back memory used by string
 //
 // Input:
-// - DSCPNT+0, DSCPNT+1 - pointer to string descriptor
+// - DSCPNT+1, DSCPNT+2 - pointer to string descriptor
 //
 
 // XXX test this routine
-
-// XXX handle strings located in program area
-
-// XXX change DSCPNT to use standard descriptor format
+// XXX check if this entry point is needed
 
 varstr_free:
 
@@ -23,23 +20,23 @@ varstr_free:
 	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<DSCPNT
+	ldx #<DSCPNT+1
 	jsr peek_under_roms
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_DSCPNT
+	jsr peek_under_roms_via_DSCPNT_PLUS_1
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (DSCPNT),y
+	lda (DSCPNT+1),y
 #endif
 
-	sta DSCPNT+2                                 // length of the string
+	sta DSCPNT+0                                 // length of the string
 	iny
 
 #if CONFIG_MEMORY_MODEL_60K
 	jsr peek_under_roms
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_DSCPNT
+	jsr peek_under_roms_via_DSCPNT_PLUS_1
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (DSCPNT),y
+	lda (DSCPNT+1),y
 #endif
 
 	pha
@@ -48,20 +45,30 @@ varstr_free:
 #if CONFIG_MEMORY_MODEL_60K
 	jsr peek_under_roms
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_DSCPNT
+	jsr peek_under_roms_via_DSCPNT_PLUS_1
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (DSCPNT),y
+	lda (DSCPNT+1),y
 #endif
 
-	sta DSCPNT+1
+	sta DSCPNT+2
 	pla
-	sta DSCPNT+0
+	sta DSCPNT+1
+
+	// FALLTROUGH
+
+varstr_free_DSCPNT_set:
+
+	// consider moving size check (DSCPNT+0) here
+
+	// XXX
+	// XXX check if string is located above FRETOP, handle case if it is not
+	// XXX
 
 	// Quick check - is the string the lowest one?
 
 	cmp FRETOP+0
 	bne varstr_free_inside
-	lda DSCPNT+1
+	lda DSCPNT+2
 	cmp FRETOP+1
 	bne varstr_free_inside
 
@@ -73,7 +80,7 @@ varstr_free:
 #if !HAS_OPCODES_65CE02
 
 	lda #$02                                     // free the back-pointer
-	sta DSCPNT+2
+	sta DSCPNT+0
 	jmp varstr_FRETOP_up
 
 #else // HAS_OPCODES_65CE02
@@ -90,7 +97,7 @@ varstr_free_inside:
 	// This is not the lowest string; mark it as free
 	// First preserve the string size, it will make it easier for the garbage collector
 
-	lda DSCPNT+2
+	lda DSCPNT+0
 	tay
 	dey
 
@@ -101,14 +108,14 @@ varstr_free_inside:
 	sta (FRETOP), y
 #endif
 
-	// Now increase DSCPNT+0/+1 to point to the back-pointer
+	// Now increase DSCPNT+1/+2 to point to the back-pointer
 
 	clc
-	lda DSCPNT+0
-	adc DSCPNT+2
-	sta DSCPNT+0
+	lda DSCPNT+1
+	adc DSCPNT+0
+	sta DSCPNT+1
 	bcc !+
-	inc DSCPNT+1
+	inc DSCPNT+2
 !:
 	// Fill the back-pointer with 0
 
@@ -116,10 +123,10 @@ varstr_free_inside:
 	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<DSCPNT
+	ldx #<DSCPNT+1
 	jsr poke_under_roms
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	sta (DSCPNT), y
+	sta (DSCPNT+1), y
 #endif
 
 	iny                                          // $00 -> $01
@@ -127,6 +134,6 @@ varstr_free_inside:
 #if CONFIG_MEMORY_MODEL_60K
 	jmp poke_under_roms
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	sta (DSCPNT), y
+	sta (DSCPNT+1), y
 	rts
 #endif