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68 lines
1.7 KiB
ArmAsm
68 lines
1.7 KiB
ArmAsm
;
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; 2012-09-04, Oliver Schmidt
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; 2019-11-08, Greg King
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;
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; unsigned char getfirstdevice (void);
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; unsigned char __fastcall__ getnextdevice (unsigned char device);
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;
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.export _getfirstdevice
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.export _getnextdevice
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.import isdisk
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.import opencmdchannel
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.import closecmdchannel
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.importzp tmp2
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.include "cx16.inc"
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;------------------------------------------------------------------------------
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; getfirstdevice()
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_getfirstdevice:
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lda #$FF
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; Fall through
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;------------------------------------------------------------------------------
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; getnextdevice()
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_getnextdevice:
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tax
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next: inx
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cpx #$FF
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beq done
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; [open|close]cmdchannel already call isdisk internally; but, they
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; interpret a non-disk as a no-op, while we need to interpret it
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; as an error here.
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jsr isdisk
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bcs next
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; [open|close]cmdchannel don't call into the Kernal, at all, if they
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; only [in|de]crement the reference count of the shared cmdchannel.
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; Therefore, we need to initiate STATUS explicitly here.
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lda #$00
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sta STATUS
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stx tmp2
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jsr opencmdchannel
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ldx tmp2
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jsr closecmdchannel
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ldx tmp2
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; As we had to reference STATUS above anyway, we can do so, as well,
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; here too (instead of calling READST).
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lda STATUS
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; Either the Kernal calls above were successfull, or there was
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; already a cmdchannel to the device open -- which is a pretty
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; good indication of its existence. ;-)
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bmi next
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done: txa
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ldx #$00
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rts
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