beginning of dummy string memory management

c64/aliases/,aliases_ram_lowmem.s

@@ -28,9 +28,9 @@
 	.label TANSGN    = $12 //          -- NOT IMPLEMENTED --
 	.label CHANNL    = $13 //          -- NOT IMPLEMENTED --
 	.label LINNUM    = $14 // $14-$15  BASIC line number, [!] also used by DOS Wedge
-	.label TEMPPT    = $16 //          -- NOT IMPLEMENTED --
-	.label LASTPT    = $17 // $17-$18  -- NOT IMPLEMENTED --
-	.label TEMPST    = $19 // $19-$21  -- NOT IMPLEMENTED --
+	.label TEMPPT    = $16 //          pointer to the first available slot in the temporary string descriptor stack
+	.label LASTPT    = $17 // $17-$18  pointer to the last used slot in the temporary string descriptor
+	.label TEMPST    = $19 // $19-$21  temporary string stack descriptors
 	.label INDEX     = $22 // $22-$25  temporary variables, [!] our usage might be different
 	.label RESHO     = $26 // $26-$2A  -- NOT IMPLEMENTED --
 	.label TXTTAB    = $2B // $2B-$2C  start of BASIC code

c64/basic/basic_do_new.s

@@ -73,11 +73,14 @@ basic_do_clr:
 	sta MEMSIZ+0
 	sta FRETOP+0
 
-	// FALL THROUGH
+	// FALLTHROUGH
 
 basic_do_clr:
 
+	// XXX shouldnt FRETOP go here?
+
 	// Clear variables, arrays and strings
+
 	lda VARTAB+0
 	sta ARYTAB+0
 	sta STREND+0
@@ -87,4 +90,5 @@ basic_do_clr:
 
 	rts
 
+
 #endif // ROM layout

c64/basic/engine/ad9e.frmevl.s

@@ -11,7 +11,6 @@
 //
 // Output:
 // - VALTYP - $00 = floating number, $FF = string
-// - INTFLG (XXX float/integer, probably)
 // - for float: FAC1
 // - for string: __FAC1 + 0 = length, __FAC1 + 1 = pointer to string
 //
@@ -20,20 +19,11 @@
 //   in a correct order
 //
 
-// XXX finish the implementation
+// XXX finish the implementation: invoking functions, fetcching PI, fetching float, fetching variables
 
 
 FRMEVL:
 
-	// XXX we neeed FRETOP for string concatenation
-
-	// lda VARTAB+0
-	// sta FRETOP+0
-	// lda VARTAB+1
-	// sta FRETOP+1
-
-	// XXX we also need TEMMPPT, LASTPT and TEMPST
-
 	// Push the sentinel to the stack
 
 	lda #$00
@@ -72,7 +62,7 @@ FRMEVL_loop:
 	// Check for the PI
 
 	cmp #$FF                           // check for PI
-	beq_16 FRMEVL_fetch_PI             // XXX
+	beq_16 FRMEVL_fetch_PI
 
 	// If not a PI and not an unary operator, than everything above
 	// $7F has to be a function
@@ -256,16 +246,16 @@ FRMEVL_push_value_operator:
 
 FRMEVL_push_string:
 
-	// Push string - address, length, type
+	// Push string - length, address, type
+
+	lda __FAC1+0
+	pha
 
 	lda __FAC1+1
 	pha
 	lda __FAC1+2
 	pha
 
-	lda __FAC1+0
-	pha
-
 	txa
 	pha
 

c64/basic/engine/alloc_temp_string.s

@@ -0,0 +1,81 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Allocates area for a temporary string
+//
+// Input:
+// - .A - string length
+//
+
+
+// XXX - this is a dummy implementation, until proper string handling is implemented
+// XXX - addresses are probably wrong, debug it
+
+
+alloc_temp_string:
+
+	// Check if temporary descriptor stack has a free slot
+
+	ldx LASTPT
+	cpx #$1F
+	bcs_16 do_FORMULA_TOO_COMPLEX_error
+
+	// Prepare data in index registers
+
+	tay                                // store length, we will need .A in a moment
+
+	// Increment temporary descriptor stack pointers by 3
+
+	lda LASTPT
+	adc #$03                           // Carry is already clear here
+	sta LASTPT
+	adc #$03
+	sta TEMPPT
+
+	// Fill in the new entry
+
+	cmp #$1C
+	bne !+
+
+	// Fill in the address - first entry
+
+	ldx TEMPPT
+	lda STREND+0
+	sta $01, x                    // address - lo byte
+	lda STREND+1
+	sta $02, x                    // address - hi byte
+
+	jmp alloc_temp_string_space_check
+!:
+	// Fill in the adress - use previous entry
+
+	ldx LASTPT
+	lda $01, x                   // address - lo byte
+	ldx TEMPPT
+	sta $01, x
+
+	ldx LASTPT
+	lda $02, x                   // address - hi byte
+	ldx TEMPPT
+	sta $02, x
+	inc $02, x
+
+	// FALLTROUGH
+
+alloc_temp_string_space_check:
+
+	// Fill in the length of the new string
+
+	ldx TEMPPT
+	tya
+	sta $00, x                    // length
+
+	// Check if we have enough space
+
+	lda $02, x
+	cmp FRETOP+1
+	beq_16 do_OUT_OF_MEMORY_error
+
+	rts

c64/basic/engine/execute_line_statements.s

@@ -32,6 +32,14 @@ execute_statements:
 	cmp #$7F
 	bcc_16 do_SYNTAX_error             // branch if not a token    XXX here we should handle variable assignments
 
+	// Initialize temporary string stack - just about any statement might need it
+	// XXX original C64 ROM initializes this during the startup too - not sure where to put this
+
+	ldx #$16
+	stx LASTPT
+	ldx #$19
+	stx TEMPPT
+
 #if !HAS_OPCODES_65C02
 
 	// Get the jump table entry for it, push it on the stack, and then RTS to start it.

c64/basic/operators/oper_add.s

@@ -25,11 +25,6 @@ oper_add_floats:
 
 oper_add_strings:
 
-	// Pull string length
-
-	pla
-	sta __FAC2+0
-
 	// Retrieve string address
 
 	pla
@@ -37,6 +32,41 @@ oper_add_strings:
 	pla
 	sta __FAC2+1
 
-	// XXX merge strings here
+	// Pull string length
+
+	pla
+	sta __FAC2+0
+	beq oper_add_strings_end           // if string 2 is empty, we have nothing to do
+
+	// If string 1 is empty, just copy the metadata
+
+	lda __FAC1+0
+	bne !+
+
+	lda __FAC2+0
+	sta __FAC1+0
+	lda __FAC2+1
+	sta __FAC1+1
+	lda __FAC2+2
+	sta __FAC1+2
+
+	jmp FRMEVL_continue
+!:
+	// Allocate memory for concatenated string
+
+	clc
+	adc __FAC2+0
+	bcs_16 do_STRING_TOO_LONG_error
+
+	jsr alloc_temp_string
+
+.break
+
+
+
+	// XXX finish the implementation
+
+
+oper_add_strings_end:
 
 	jmp FRMEVL_continue