begin implementing memory copy routines for inserting and deleting BASIC lines.

c64/basic/under_rom_routines.s

@@ -20,6 +20,43 @@ install_ram_routines:
 	sta $FFFF
 
 	rts
+
+basic_shift_mem_up_and_relink:
+	;; Shift memory up from basic_current_line_ptr
+	;; X bytes.
+
+	;; Work out end point of destination
+	txa
+	clc
+	adc basic_end_of_text_ptr+0
+	sta memmove_dst+0
+	lda basic_end_of_text_ptr+1
+	adc #0
+	sta memmove_dst+1
+	;; End point of source is just current end of BASIC text
+	lda basic_end_of_text_ptr+0
+	sta memmove_src
+	lda basic_end_of_text_ptr+1
+	sta memmove_src+1
+
+	;; Work out size of region to copy
+	lda basic_end_of_text_ptr+1
+	sec
+	sbc basic_current_line_ptr+1
+	sta memmove_size+1
+	lda basic_end_of_text_ptr+0
+	sbc #0
+	sta memmove_size+0
+
+	;; To make life simple for the copy routine that lives in RAM,
+	;; we have to adjust the end pointers down one page and set Y to the low
+	;; byte of the copy size.
+	tay
+	dec memmove_src+1
+	dec memmove_dst+1
+
+	;; Do the copy
+	jmp shift_mem_up
 	
 ram_routines_start:	
 
@@ -27,6 +64,28 @@ tiny_nmi_handler_routine:
 	inc missed_nmi_flag
 	rti
 
+shift_mem_up_routine:
+	;; Move memmove_size bytes from memmove_src to memmove_dst,
+	;; where memmove_dst > memmove_src
+	;; This means we have to copy from the back end down.
+	;; This routine assumes the pointers are already pointed
+	;; to the end of the areas, and that Y is correctly initialised
+	;; to allow the copy to begin.
+	jsr memmap_allram
+smu1:	
+	lda (memmove_src),y
+	sta (memmove_dst),y
+	dey
+	cpy #$ff
+	bne smu1
+	dec memmove_src+1
+	dec memmove_dst+1
+	dec memmove_size+1
+	bne smu1
+	
+	jmp memmap_normal
+	
+	
 peek_under_roms_routine:
 	stx peek_under_roms+7 	;Offset of arg of lda ($00),y
 	jsr memmap_allram