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|
;
; Christian Groessler, May 2002
;
; this file provides the lseek() function
;
; off_t __fastcall__ lseek(int fd, off_t offset, int whence);
;
.export _lseek
.import incsp6,__oserror
.import __inviocb,ldax0sp,ldaxysp,fdtoiocb
.import __dos_type
.import fd_table
.importzp sreg,ptr1,ptr2,ptr3,ptr4
.importzp tmp1,tmp2,tmp3
.include "atari.inc"
.include "errno.inc"
.include "fd.inc"
; seeking not supported, return -1 and ENOSYS errno value
no_supp:jsr incsp6
lda #<ENOSYS
jsr __directerrno ; returns with $FFFF in AX
sta sreg
sta sreg+1
rts
parmerr:
iocberr:jsr incsp6
ldx #255
stx sreg
stx sreg+1
jmp __inviocb
; lseek() entry point
.proc _lseek
cpx #0 ; sanity check whence parameter
bne parmerr
cmp #3 ; valid values are 0..2
bcs parmerr
sta tmp1 ; remember whence
ldy #5
jsr ldaxysp ; get fd
jsr fdtoiocb ; convert to iocb in A, fd_table index in X
bmi iocberr
sta tmp3 ; remember iocb
jsr chk_supp ; check, whether seeking is supported by DOS/Disk
bcc no_supp
ldx tmp1 ; whence
beq cur
dex
beq end
; SEEK_SET
dex
stx ptr3
stx ptr3+1
stx ptr4
stx ptr4+1
beq cont
; SEEK_CUR
cur: ldx tmp3
lda #NOTE
sta ICCOM,x
jsr CIOV ; read it
bmi xxerr
l01: lda ICAX3,x ; low byte of position
sta ptr3
lda ICAX4,x ; med byte of position
sta ptr3+1
lda ICAX5,x ; high byte of position
sta ptr4
lda #0
sta ptr4+1
beq cont
; SEEK_END
end: ldx tmp3
lda #GETFL
sta ICCOM,x
jsr CIOV
bpl l01
; error returned from CIO
xxerr: tya
pha
jsr incsp6
pla
jsr __mappederrno ; returns with $FFFF in AX
sta sreg
sta sreg+1
rts
; check for offset 0, SEEK_CUR (get current position)
cont: ldy #3
jsr ldaxysp ; get upper word
sta ptr1
stx ptr1+1
jsr ldax0sp ; get lower word
stx tmp2
ora tmp2
ora ptr1
ora ptr1+1
bne seek
lda tmp1 ; whence (0 = SEEK_CUR)
bne seek
; offset 0, SEEK_CUR: return current fp
ret: jsr incsp6
lda ptr4+1
sta sreg+1
lda ptr4
sta sreg
ldx ptr3+1
lda ptr3
.if 0
; return exactly the position DOS has
ldx tmp3
lda #NOTE
sta ICCOM,x
jsr CIOV ; read it
bmi xxerr
lda #0
sta sreg+1
lda ICAX5,x ; high byte of position
sta sreg
lda ICAX3,x ; low byte of position
pha
lda ICAX4,x ; med byte of position
tax
pla
.endif
rts
parmerr1: jmp parmerr
; we have to call POINT
seek: jsr ldax0sp ; get lower word of new offset
clc
adc ptr3
sta ptr3
txa
adc ptr3+1
sta ptr3+1
lda ptr1
adc ptr4
sta ptr4
lda ptr1+1
adc ptr4+1
sta ptr4+1
bne parmerr1 ; resulting value too large
ldx tmp3 ; IOCB
lda ptr3
sta ICAX3,x
lda ptr3+1
sta ICAX4,x
lda ptr4
sta ICAX5,x
lda #POINT
sta ICCOM,x
jsr CIOV
bpl ret
bmi xxerr
.endproc
; check whether seeking is supported
; tmp3: iocb
; X: index into fd_table
;
; On non-SpartaDOS, seeking is not supported.
; We check, whether CIO function 39 (get file size) returns OK.
; If yes, NOTE and POINT work with real file offset.
; If not, NOTE and POINT work with the standard ScNum/Offset values.
; We remember a successful check in fd_table.ft_flag, bit 3.
chk_supp:
lda fd_table+ft_flag,x
and #8
bne supp
; do the test
lda __dos_type
cmp #SPARTADOS
beq :+
cmp #BWDOS
beq :+
cmp #REALDOS
bne ns1
: txa
pha
lda DOS+1 ; get SpartaDOS version
cmp #$40
bcs supp1 ; SD-X (ver 4.xx) supports seeking on all disks
ldx tmp3 ; iocb to use
lda #GETFL
sta ICCOM,x
jsr CIOV
bmi notsupp ; error code ? should be 168 (invalid command)
; seeking is supported on this DOS/Disk combination
supp1: pla
tax
lda #8
ora fd_table+ft_flag,x
sta fd_table+ft_flag,x
supp: sec
rts
notsupp:pla
ns1: clc
rts
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