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|
;
; Christian Groessler, May-2000
;
; fd indirection table & helper functions
;
.include "atari.inc"
.include "fd.inc"
.importzp tmp1,tmp2,tmp3,ptr4,sp
.import fd_table,fd_index
.import fdt_to_fdi
.export clriocb
.export fdtoiocb_down
.export fddecusage
.export newfd
.code
; gets fd in ax, decrements usage counter
; return iocb index in X
; return N bit set for invalid fd
; return Z bit set if last user
; all registers destroyed
.proc fdtoiocb_down
cpx #0
bne inval
cmp #MAX_FD_INDEX
bcs inval
tax
lda fd_index,x ; get index
tay
lda #$ff
sta fd_index,x ; clear entry
tya
asl a ; create index into fd table
asl a
tax
lda #$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 ok_notlast ; 0? (shouldn't happen)
sec
sbc #1 ; decr usage counter
sta fd_table+ft_usa,x
retiocb:php
txa
tay
lda fd_table+ft_iocb,x ; get iocb
tax
plp
bne cont
lda #$ff
sta fd_table+ft_iocb,y ; clear table entry
lda fd_table+ft_flag,y
and #16 ; opened by app?
eor #16 ; return set Z if yes
cont: rts
ok_notlast:
lda #1 ; clears Z
jmp retiocb
.endproc ; fdtoiocb_down
inval: ldx #$ff ; sets N
rts
; clear iocb except for ICHID field
; expects X to be index to IOCB (0,$10,$20,etc.)
; all registers destroyed
.proc clriocb
inx ; don't clear ICHID
ldy #15
lda #0
loop: sta ICHID,x
inx
dey
bne loop
rts
.endproc
; decrements usage counter for fd
; if 0 reached, it's marked as unused
; get fd index in tmp2
; Y register preserved
.proc fddecusage
lda tmp2 ; get fd
cmp #MAX_FD_INDEX
bcs ret ; invalid index, do nothing
tax
lda fd_index,x
pha
lda #$ff
sta fd_index,x
pla
asl a ; create index into fd table
asl a
tax
lda #$ff
cmp fd_table+ft_iocb,x ; entry in use?
beq ret ; no, do nothing
lda fd_table+ft_usa,x ; get usage counter
beq ret ; 0? should not happen
sec
sbc #1 ; decrement by one
sta fd_table+ft_usa,x
bne ret ; not 0
lda #$ff ; 0, table entry unused now
sta fd_table+ft_iocb,x ; clear table entry
ret: rts
.endproc ; fddecusage
; newfd
;
; called from open() function
; finds a fd to use for an open request
; checks whether it's a device or file (file: characters follow the ':')
; files always get an exclusive slot
; for devices it is checked whether the device is already open, and if yes,
; a link to this open device is returned
;
; Calling parameters:
; tmp3 - length of filename + 1
; AX - points to filename
; Y - iocb to use (if we need a new open)
; Return parameters:
; tmp2 - fd num ($ff and C=0 in case of error - no free slot)
; C - 0/1 for no open needed/open should be performed
; all registers preserved!
.bss
; local variables:
loc_Y: .res 1
loc_ptr4_l: .res 1
loc_ptr4_h: .res 1
loc_tmp1: .res 1
loc_devnum: .res 1
loc_size: .res 1
.code
.proc newfd
pha
txa
pha
tya
pha
ldx #0
stx loc_devnum
lda tmp1
sta loc_tmp1
stx tmp1 ; init tmp1
stx tmp2 ; init tmp2
lda ptr4+1
sta loc_ptr4_h
lda ptr4
sta loc_ptr4_l
pla
sta loc_Y
pla
sta ptr4+1
pla
sta ptr4
; ptr4 points to filename
ldy #1
lda #':'
cmp (ptr4),y ; "X:"
beq colon1
iny
cmp (ptr4),y ; "Xn:"
beq colon2
; no colon there!? OK, then we use a fresh iocb....
; return error here? no, the subsequent open call should fail
do_open_nd: ; do open and don't remember device
lda #2
sta tmp1
do_open:lda tmp1
ora #1
sta tmp1 ; set flag to return 'open needed' : C = 1
ldx #ft_iocb
ldy #$ff
srchfree:
tya
cmp fd_table,x ; check ft_iocb field for $ff
beq freefnd ; found a free slot
txa
clc
adc #ft_entrylen
tax
cmp #(MAX_FD_VAL*4)+ft_iocb ; end of table reached?
bcc srchfree
; error: no free slot found
noslot: ldx #0
stx tmp1 ; return with C = 0
dex
stx tmp2 ; iocb: $ff marks error
jmp finish
; found a free slot
freefnd:txa
sec
sbc #ft_iocb ; normalize
tax
lsr a
lsr a
sta tmp2 ; return fd
lda #2
bit tmp1 ; remember device?
beq l1 ; yes
lda #0 ; no, put 0 in field
beq l2
l1: ldy #0
lda (sp),y ; get device
l2: sta fd_table+ft_dev,x ; set device
lda #1
sta fd_table+ft_usa,x ; set usage counter
lda loc_Y
sta fd_table+ft_iocb,x ; set iocb index
lda loc_devnum
and #7 ; device number is 3 bits
ora #16 ; indicated a fd actively opened by the app
sta fd_table+ft_flag,x
lda tmp2
jsr fdt_to_fdi ; get new index
noslot1:bcs noslot ; no one available (noslot1: helper label for branch out of range)
;cmp #$ff ; no one available
;beq noslot ;@@@ cleanup needed
sta tmp2 ; return index
jmp finish
; string in "Xn:xxx" format
colon2: dey
lda (ptr4),y ; get device number
sec
sbc #'0'
and #7
sta loc_devnum
sta tmp2 ; save it for speed later here also
lda #4 ; max. length if only device + number ("Xn:")
cmp tmp3
bcc do_open_nd ; string is longer -> contains filename
bcs check_dev ; handle device only string
; string in "X:xxx" format
colon1: lda #3 ; max. length if device only ("X:")
cmp tmp3
bcc do_open_nd ; string is longer -> contains filename
; get device and search it in fd table
check_dev:
ldy #0
lda (ptr4),y ; get device id
tay
ldx #(MAX_FD_VAL*4) - ft_entrylen
srchdev:lda #$ff
cmp fd_table+ft_iocb,x ; is entry valid?
beq srch2 ; no, skip this entry
tya
cmp fd_table+ft_dev,x
beq fnddev
srch2: txa
sec
sbc #ft_entrylen+1
tax
bpl srchdev
; not found, open new iocb
jmp do_open
; found device in table, check device number (e.g R0 - R3)
fnddev: lda fd_table+ft_flag,x
and #7
cmp tmp2 ; contains devnum
bne srch2 ; different device numbers
; found existing open iocb with same device
txa
lsr a
lsr a
sta tmp2
inc fd_table+ft_usa,x ; increment usage counter
jsr fdt_to_fdi ; get new index
bcs noslot1 ; no one available
sta tmp2 ; return index
; clean up and go home
finish: lda ptr4
pha
lda ptr4+1
pha
lda loc_Y
pha
lda tmp1
pha
lda loc_tmp1
sta tmp1
pla
lsr a ; set C as needed
pla
tay
pla
tax
pla
rts
.endproc ; newfd
|
