53dd513176
which included commits to RCS files with non-trunk default branches. git-svn-id: svn://svn.cc65.org/cc65/trunk@3 b7a2c559-68d2-44c3-8de9-860c34a00d81
103 lines
1.7 KiB
ArmAsm
103 lines
1.7 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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.export fdtoiocb
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.export fdtoiocb_down
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.export fd_table
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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.), $ff for empty entry
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ft_dev = 2 ; device of open iocb
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ft_flag = 3 ; flags
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.code
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; gets fd in ax, decrements usage counter
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; return iocb index in X
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; return N bit set for invalid fd
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; return Z bit set if last user
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; all registers destroyed
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.proc fdtoiocb_down
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cpx #0
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bne inval
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cmp #MAX_FD_VAL
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bcs inval
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asl a ; create index into fd table
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asl a
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tax
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lda #$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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