begin implementing basic text manipulation routines.

c64/basic/basic_find_line.s

@@ -0,0 +1,46 @@
+	;; Find the BASIC line with number basic_line_number
+
+
+basic_find_line:
+	;; Get pointer to start of BASIC text
+	lda basic_start_of_text_ptr+0
+	sta basic_current_line_ptr+0
+	lda basic_start_of_text_ptr+1
+	sta basic_current_line_ptr+1
+
+basic_find_line_loop:	
+	;; Then search for line number
+	;; Line number 
+	ldy #2
+	ldx #<basic_current_line_ptr
+	jsr peek_under_roms
+	cmp basic_line_number+0
+	bne not_this_line
+	iny
+	jsr peek_under_roms
+	cmp basic_line_number+1
+	bne not_this_line
+
+	clc
+	rts
+not_this_line:
+	;; Not this line, so advance to next line
+	ldy #0
+	ldx #<basic_current_line_ptr
+	jsr peek_under_roms
+	bne more_lines_exist
+	iny
+	jsr peek_under_roms
+	bne more_lines_exist
+	;; no more lines exist, return failure
+	sec
+	rts
+more_lines_exist:	
+	;; A = high byte of line
+	pha
+	dey
+	jsr peek_under_roms
+	sta basic_current_line_ptr+0
+	pla
+	sta basic_current_line_ptr+1
+	jmp basic_find_line_loop