implemented CLALL routine, added support for LAT/SAT/FAT and LDTND variables

c64/kernal/close.s

@@ -1,3 +1,41 @@
 ; Function defined on pp272-273 of C64 Programmers Reference Guide
 close:
+
+	;; Implemented accorging to 'C64 Programmers Reference Guide', page 281
+
+	;; XXX this needs more testing (opening 10 files at once, closing in various orders, etc) once the code is more mature
+	
+	;; Find the LAT / SAT / FAT entry which LAT corresponds to A
+	
+	ldy LDTND
+	beq close_error_not_found ; table empty
+*
+	dey
+	bmi close_error_not_found ; no more entries
+	cmp LAT, y
+	bne - ; does not match, try the next one
+	
+	;; We have the entry index in Y
+	
+	;; XXX some devices (like IEC) needs special support here, to free their internal resources!
+	;; Just make sure the Y register value is kept, or redo ldy DFTLN
+*
+	iny
+	cpy #$0A
+	bpl +
+	lda LAT, y
+	sta LAT-1, y
+	lda FAT, y
+	sta FAT-1, y
+	lda SAT, y
+	sta SAT-1, y
+	jmp -
+*
+	;; Decrement the list size variable
+	dec LDTND
+	;; FALLTHROUGH (for now) - success
+	
+close_error_not_found:
+	
+	;; XXX it seems that this function can't report errors, am I right?
 	rts