blob: f01cc04b974dd5d1d1571d894c5a0a30a6901d96 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
|
; in C:
;; /* arg points to something like:
;; "part #channel I'm outta here\0"
;; after nextarg(), arg points to "part\0" only, and ret points
;; to "#channel I'm outta here\0". */
;; char *nextarg(char *arg) {
;; /* iterate over the first word */
;; while(*arg && *arg != ' ')
;; arg++;
;;
;; /* if we found a space, replace it with a null terminator */
;; if(*arg)
;; *arg++ = 0;
;; else
;; return 0; /* found no space, there's no next arg! */
;;
;; /* skip space(s) */
;; while(*arg && *arg == ' ')
;; arg++;
;;
;; if(*arg)
;; return arg;
;;
;; return 0;
;; }
; ...which compiles to ~175 bytes. we can do better in asm.
.export _nextarg
.importzp ptr1
incptr1:
inc ptr1
bne @ret
inc ptr1+1
@ret:
rts ; always returns with Z flag clear (unless we roll over $FFFF -> 0!)
_nextarg:
sta ptr1
stx ptr1+1
ldy #0 ; actually this stays 0 the while time
; skips over the first word (aka sequence of non-spaces)
@skipword:
lda (ptr1),y
beq @ret0 ; found a null byte, return null (there is no next arg).
cmp #' '
beq @foundspc
jsr incptr1
bne @skipword ; branch always
@foundspc:
; ptr1 now points to a space.
tya ; 0
sta (ptr1),y ; null out the space
jsr incptr1
@skipspc:
lda (ptr1),y
beq @ret0 ; found a null byte, return null (there is no next arg).
cmp #' '
bne @done
jsr incptr1
bne @skipspc
@done:
lda ptr1
ldx ptr1+1
rts
@ret0:
lda #0
tax
rts
|
