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230 lines
3.8 KiB
ArmAsm
230 lines
3.8 KiB
ArmAsm
;
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; Christian Groessler, May-2000
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;
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; fd indirection table & helper functions
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;
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.include "atari.inc"
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.importzp tmp2,ptr4,sp
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.import subysp,addysp
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.export fdtoiocb
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.export fdtoiocb_down
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.export fd_table
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.export fddecusage
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.export newfd
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.data
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fd_table:
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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.byte 0,$ff,0,0
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MAX_FD_VAL = (* - fd_table) / 4
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ft_usa = 0 ; usage counter
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ft_iocb = 1 ; iocb index (0,$10,$20,etc.), $ff for empty entry
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ft_dev = 2 ; device of open iocb
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ft_flag = 3 ; flags
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; lower 3 bits: device number (for R: and D:)
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.code
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; gets fd in ax, decrements usage counter
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; return iocb index in X
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; return N bit set for invalid fd
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; return Z bit set if last user
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; all registers destroyed
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.proc fdtoiocb_down
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cpx #0
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bne inval
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cmp #MAX_FD_VAL
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bcs inval
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asl a ; create index into fd table
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asl a
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tax
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lda #$ff
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cmp fd_table+ft_iocb,x ; entry in use?
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beq inval ; no, return error
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lda fd_table+ft_usa,x ; get usage counter
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beq ok_notlast ; 0?
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sec
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sbc #1 ; decr usage counter
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sta fd_table+ft_usa,x
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retiocb:php
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txa
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tay
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lda fd_table+ft_iocb,x ; get iocb
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tax
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plp
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bne cont
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php
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lda #$ff
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sta fd_table+ft_iocb,y ; clear table entry
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plp
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cont: rts
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ok_notlast:
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lda #1 ; clears Z
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jmp retiocb
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.endproc
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inval: ldx #$ff ; sets N
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rts
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; gets fd in ax
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; return iocb index in X
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; return N bit set for invalid fd
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; all registers destroyed
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.proc fdtoiocb
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cpx #0
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bne inval
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cmp #MAX_FD_VAL
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bcs inval
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asl a ; create index into fd table
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asl a
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tax
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lda #$ff
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cmp fd_table+ft_iocb,x ; entry in use?
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beq inval ; no, return error
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lda fd_table+ft_usa,x ; get usage counter
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beq inval ; 0? should not happen
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lda fd_table+ft_iocb,x ; get iocb
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rts
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.endproc
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; decrements usage counter for fd
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; if 0 reached, it's marked as unused
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; get fd index in tmp2
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; Y register preserved
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.proc fddecusage
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lda tmp2 ; get fd
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cmp #MAX_FD_VAL
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bcs ret ; invalid index, do nothing
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asl a ; create index into fd table
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asl a
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tax
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lda #$ff
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cmp fd_table+ft_iocb,x ; entry in use?
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beq ret ; no, do nothing
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lda fd_table+ft_usa,x ; get usage counter
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beq ret ; 0? should not happen
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sec
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sbc #1 ; decrement by one
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sta fd_table+ft_usa,x
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bne ret ; not 0
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lda #$ff ; 0, table entry unused now
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sta fd_table+ft_iocb,x ; clear table entry
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ret: rts
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.endproc
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; newfd
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;
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; called from open() function
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; finds a fd to use for an open request
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; checks whether it's a device or file (file: characters following the ':')
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; files always get an exclusive slot
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; for devices it is checked whether the device is already open, and if yes,
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; a link to this open device is returned
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;
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; Calling paramteter:
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; AX - points to filename
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; Y - iocb to use (if we need a new open)
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; Return parameters:
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; tmp2 - fd num
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; C - 0/1 for no open needed/open should be performed
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; all registers preserved!
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; local variables:
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; AX - 0 (A-0,X-1)
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; Y - 2
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; ptr4 - 3,4 (backup)
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; devnum - 5
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loc_A = 0
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loc_X = 1
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loc_Y = 2
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loc_ptr4_l = 3
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loc_ptr4_h = 4
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loc_devnum = 5
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loc_size = 6
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.proc newfd
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pha
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txa
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pha
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tya
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pha
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ldy #loc_size
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jsr subysp
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ldy #loc_devnum
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lda #0
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sta (sp),y ; loc_devnum
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dey
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lda ptr4+1
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sta (sp),y ; loc_ptr4_h
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dey
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lda ptr4
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sta (sp),y ; loc_ptr4_l
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dey
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pla
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sta (sp),y ; loc_Y
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dey
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pla
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sta (sp),y ; loc_X
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sta ptr4+1
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dey
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pla
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sta (sp),y ; loc_A
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sta ptr4
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; ptr4 points to filename
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ldy #1
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lda #':'
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cmp (ptr4),y ; "X:"
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beq colon1
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iny
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cmp (ptr4),y ; "Xn:"
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beq colon2
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; no colon there!? OK, then we use a fresh iocb....
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do_open:nop ; @@@TODO
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ldy #loc_size
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jsr addysp
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rts
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colon2: dey
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tya
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pha
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lda (ptr4),y ; get device number
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sec
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sbc #'0'
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ldy #loc_devnum
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sta (sp),y ; save it
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pla
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tay
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colon1:
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.endproc
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