more work on string support

src/basic/basic_commands/cmd_let.s

@@ -9,9 +9,19 @@ cmd_let:
 	// Fetch variable name, should be followed by assign operator
 
 	jsr fetch_variable
+
+#if HAS_OPCODES_65CE02
 	bcs_16 do_SYNTAX_error
 	jsr injest_assign
 	bcs_16 do_SYNTAX_error
+#else
+	bcs !+
+	jsr injest_assign
+	bcc !++
+!:
+	jmp do_SYNTAX_error
+!:
+#endif
 
 	// Determine variable type and push it to the stack
 
@@ -149,12 +159,67 @@ cmd_let_assign_string:
 
 	// First special case - check if the new string has size 0
 
-	lda DSCPNT+0
+	lda __FAC1+0
 	bne cmd_let_assign_string_not_empty
 
-	// XXX free old string data
+	// Yes, it is empty - check if the old one is, free it if necessary
 
-	// Set the new variable as size 0
+	lda DSCPNT+0
+	bne !+
+	jsr varstr_free_DSCPNT_set
+!:
+	// Set the new variable as empty string
+
+	ldy #$00
+	lda #$00
+
+#if CONFIG_MEMORY_MODEL_60K
+	ldx #<VARPNT
+#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	sta (VARPNT), y
+#endif
+
+	rts
+
+cmd_let_assign_string_not_empty:
+
+	// Check if the source and destination strings are the same
+
+	lda DSCPNT+1
+	cmp __FAC1+1
+	bne cmd_let_assign_string_not_same
+	iny
+	lda DSCPNT+2
+	cmp __FAC1+2
+	bne cmd_let_assign_string_not_same
+
+	// If we are here, than both source and destination strings are the same - nothing more to be done
+
+	rts
+
+cmd_let_assign_string_not_same:
+.break
+	// XXX something is wrong with checks below
+
+	// Strings are not the same - check if the new one is located within the text area, between TXTTAB and VARTAB
+
+	lda TXTTAB+1
+	cmp __FAC1+2
+	bcc cmd_let_assign_string_not_text_area
+	bne !+
+	lda TXTTAB+0
+	cmp __FAC1+1
+	bcc cmd_let_assign_string_not_text_area
+!:
+	lda __FAC1+2
+	cmp VARTAB+1
+	bcc cmd_let_assign_string_not_text_area
+	bne !+
+	lda __FAC1+1
+	cmp VARTAB+0
+	bcc cmd_let_assign_string_not_text_area	
+!:
+	// String is located within text area - great, just copy the descriptor
 
 #if CONFIG_MEMORY_MODEL_60K
 	
@@ -164,30 +229,21 @@ cmd_let_assign_string:
 
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 
+	ldy #$00
+	lda __FAC1+0
+	sta (VARPNT), y
+	iny
+	lda __FAC1+1
+	sta (VARPNT), y
+	iny
+	lda __FAC1+2
+	sta (VARPNT), y
 
 #endif
 
 	rts
 
-cmd_let_assign_string_not_empty:
+cmd_let_assign_string_not_text_area:
-
-	// Check if the source and destination strings are the same (VARPNT should now point just after variable name)
-
-	lda VARPNT+0
-	cmp __FAC1+1
-	bne !+
-	iny
-	lda VARPNT+1
-	cmp __FAC1+2
-	bne !+
-
-	// If we are here, than both source and destination strings are the same - nothing more to be done
-
-	rts
-!:
-	// Strings are not the same - check if the new one is located within a text area, between TXTTAB and VARTAB
-
-	// XXX
 
 	// Check if size of both equals and the old on is above FRETOP
 

src/basic/engine/varstr_alloc.s

@@ -15,11 +15,10 @@
 // - https://sites.google.com/site/h2obsession/CBM/basic/variable-format
 //
 // Input:
-// - DSCPNT+0, DSCPNT+1 - pointer to string descriptor, first pointed byte should contain desired length
+// - DSCPNT+1, DSCPNT+2 - pointer to string descriptor, first pointed byte should contain desired length
 //
 
 // XXX test this routine
-// XXX change DSCPNT to use standard descriptor format
 
 varstr_alloc:
 
@@ -61,7 +60,7 @@ varstr_alloc_retry:
 	// Create the back-pointer to the string descriptor
 
 	ldy #$00
-	lda DSCPNT+0
+	lda DSCPNT+1
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<FRETOP
@@ -71,7 +70,7 @@ varstr_alloc_retry:
 #endif
 
 	iny
-	lda DSCPNT+1
+	lda DSCPNT+2
 
 #if CONFIG_MEMORY_MODEL_60K
 	jsr poke_under_roms
@@ -84,12 +83,12 @@ varstr_alloc_retry:
 	dey                                          // $01 -> $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
 
 	jsr varstr_FRETOP_down_A
@@ -101,7 +100,7 @@ varstr_alloc_retry:
 	lda FRETOP+0
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<DSCPNT
+	ldx #<FRETOP
 	jsr poke_under_roms
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 	sta (FRETOP), y
@@ -111,9 +110,10 @@ varstr_alloc_retry:
 	lda FRETOP+1
 
 #if CONFIG_MEMORY_MODEL_60K
+	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
 
 	// The end

src/basic/engine/varstr_alloc_fretop.s

@@ -6,15 +6,13 @@
 // Helper routines for 'varstr_alloc'
 //
 
-// XXX change DSCPNT to use standard descriptor format
+varstr_FRETOP_down_A:                  // .A - bytes to lower FRETOP, uses DSCPNT+0
 
-varstr_FRETOP_down_A:                  // .A - bytes to lower FRETOP, uses DSCPNT+2
+	sta DSCPNT+0 
-
-	sta DSCPNT+2 
 
 	sec
 	lda FRETOP+0
-	sbc DSCPNT+2 
+	sbc DSCPNT+0 
 	sta FRETOP+0
 	bcs !+
 	dec FRETOP+1

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 check if this entry point is needed
-// XXX handle strings located in program area
-
-// XXX change DSCPNT to use standard descriptor format
 
 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
+	lda DSCPNT+1
-	adc DSCPNT+2
+	adc DSCPNT+0
-	sta 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

src/basic/engine/varstr_free_fretop.s

@@ -8,11 +8,11 @@
 
 // XXX change DSCPNT to use standard descriptor format
 
-varstr_FRETOP_up:                    // DSCPNT+2 - bytes to increment FRETO, uses DSCPNT+2
+varstr_FRETOP_up:                    // DSCPNT+0 - bytes to increment FRETO
 
 	clc
 	lda FRETOP+0
-	adc DSCPNT+2
+	adc DSCPNT+0
 	sta FRETOP+0
 	bcc !+
 	inc FRETOP+1

src/basic/engine/varstr_garbage_collect.s

@@ -4,7 +4,6 @@
 
 // XXX test this routine
 
-// XXX change DSCPNT to use standard descriptor format
 
 varstr_garbage_collect:
 
@@ -323,13 +322,13 @@ varstr_garbage_collect_unused:
 
 	// XXX move these routines to separate files
 
-varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DSCPNT+2
+varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DSCPNT+0
 
-	sta DSCPNT+2 
+	sta DSCPNT+0
 
 	sec
 	lda TXTPTR+0
-	sbc DSCPNT+2 
+	sbc DSCPNT+0 
 	sta TXTPTR+0
 	bcs !+
 	dec TXTPTR+1
@@ -337,13 +336,13 @@ varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DS
 	rts
 
 
-varstr_INDEX_up_A:                     // .A - bytes to increase TXTPTR, uses DSCPNT+2
+varstr_INDEX_up_A:                     // .A - bytes to increase TXTPTR, uses DSCPNT+0
 
-	sta DSCPNT+2 
+	sta DSCPNT+0 
 
 	clc
 	lda INDEX+0
-	adc DSCPNT+2 
+	adc DSCPNT+0 
 	sta INDEX+0
 	bcc !+
 	dec INDEX+1

src/basic/memory/under_rom_peek_fetch_46k_50k.s

@@ -68,7 +68,7 @@ peek_under_roms_via_VARPNT:
 	jmp peek_under_roms_finalize
 #endif
 
-peek_under_roms_via_DSCPNT:
+peek_under_roms_via_DSCPNT_PLUS_1:
 
 	// Unmap BASIC lower ROM
 
@@ -77,7 +77,7 @@ peek_under_roms_via_DSCPNT:
 
 	// Retrieve value from under ROMs
 
-	lda (DSCPNT), y
+	lda (DSCPNT+1), y
 
 #if HAS_OPCODES_65C02
 	bra peek_under_roms_finalize