more work on inserting and deleting BASIC lines.

c64/basic/basic_shift_mem_up.s

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+
+
+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
+	jsr shift_mem_up
+	
+	;; Now fix the pointer for the BASIC lines
+
+	;; First, we need to point the current BASIC line
+	;; pointer to the previously present lines
+	stx tokenise_work3
+relink_up_next_line:	
+	ldx tokenise_work3
+	clc
+	adc basic_current_line_ptr+0
+	sta memmove_src+0
+	lda basic_current_line_ptr+1
+	adc #0
+	sta memmove_src+1
+	ldx #0
+	ldy #<basic_current_line_ptr
+	lda memmove_src+0
+	jsr poke_under_roms
+	inx
+	lda memmove_src+1
+	jsr poke_under_roms
+
+relink_up_loop:	
+	;; Now advance pointer to the next line,
+	lda memmove_src+0
+	sta basic_current_line_ptr+0
+	lda memmove_src+1
+	sta basic_current_line_ptr+1
+
+	;; Have we run out of lines to patch?
+	ldx #<basic_current_line_ptr
+	jsr peek_pointer_null_check
+	bcs relink_up_next_line
+
+	rts