.import fd_table,fd_index
.import fdt_to_fdi
.export clriocb
- .export fdtoiocb
.export fdtoiocb_down
.export findfreeiocb
.export fddecusage
cmp fd_table+ft_iocb,x ; entry in use?
beq inval ; no, return error
lda fd_table+ft_usa,x ; get usage counter
- beq ok_notlast ; 0?
+ beq ok_notlast ; 0? (shouldn't happen)
sec
sbc #1 ; decr usage counter
sta fd_table+ft_usa,x
tax
plp
bne cont
- php
lda #$ff
sta fd_table+ft_iocb,y ; clear table entry
- plp
+ lda fd_table+ft_flag,y
+ and #16 ; opened by app?
+ eor #16 ; return set Z if yes
cont: rts
ok_notlast:
.endproc
-; gets fd in ax
-; return iocb index in X
-; return N bit set for invalid fd
-; all registers destroyed
-.proc fdtoiocb
-
- cpx #0
- bne inval
- cmp #MAX_FD_INDEX
- bcs inval
- tax
- lda fd_index,x
- asl a ; create index into fd table
- asl a
- tax
- lda #$ff
- cmp fd_table+ft_iocb,x ; entry in use?
- beq inval ; no, return error
- lda fd_table+ft_usa,x ; get usage counter
- beq inval ; 0? should not happen
- lda fd_table+ft_iocb,x ; get iocb
- rts
-
-.endproc ; fdtoiocb
-
; find a free iocb
; no entry parameters
; return ZF = 0/1 for not found/found
.endproc ; findfreeiocb
+
; decrements usage counter for fd
; if 0 reached, it's marked as unused
; get fd index in tmp2
.endproc ; fddecusage
+
; newfd
;
; called from open() function
; C - 0/1 for no open needed/open should be performed
; all registers preserved!
-; local variables:
-; AX - 0 (A-0,X-1)
-; Y - 2
-; ptr4 - 3,4 (backup)
-; devnum - 5
-
.bss
+
+; local variables:
loc_Y: .res 1
loc_ptr4_l: .res 1
loc_ptr4_h: .res 1
ldy #$ff
srchfree:
tya
- cmp fd_table,x
+ cmp fd_table,x ; check ft_iocb field for $ff
beq freefnd ; found a free slot
txa
clc
lda loc_Y
sta fd_table+ft_iocb,x ; set iocb index
lda loc_devnum
- and #7 ; only 3 bits
+ and #7 ; device number is 3 bits
+ ora #16 ; indicated a fd actively opened by the app
sta fd_table+ft_flag,x
lda tmp2
jsr fdt_to_fdi ; get new index
- bcs noslot ; no one available
+noslot1:bcs noslot ; no one available (noslot1: helper label for branch out of range)
;cmp #$ff ; no one available
;beq noslot ;@@@ cleanup needed
sta tmp2 ; return index
; not found, open new iocb
jmp do_open
-; helper for branch out of range
-noslot1:jmp noslot
-
; found device in table, check device number (e.g R0 - R3)
fnddev: lda fd_table+ft_flag,x
and #7