; ; 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