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96 lines
1.8 KiB
ArmAsm
96 lines
1.8 KiB
ArmAsm
;
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; Oliver Schmidt, 15.09.2009
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;
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; ProDOS 8 I/O buffer management for memory between
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; location $0800 and the cc65 program start address
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;
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.constructor initiobuf
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.export iobuf_alloc, iobuf_free
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.import __RAM_START__
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.import incsp2, popax
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.include "zeropage.inc"
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.include "errno.inc"
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.include "filedes.inc"
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.segment "INIT"
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initiobuf:
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; Convert end address highbyte to table index
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lda #>__RAM_START__
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sec
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sbc #>$0800
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lsr
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lsr
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; Mark all remaining table entries as used
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tax
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lda #$FF
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: cpx #MAX_FDS
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bcc :+
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rts
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: sta table,x
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inx
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bne :-- ; Branch always
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; ------------------------------------------------------------------------
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.code
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iobuf_alloc:
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; Get and save "memptr"
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jsr incsp2
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jsr popax
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sta ptr1
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stx ptr1+1
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; Search table for free entry
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ldx #$00
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: lda table,x
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beq :+
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inx
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cpx #MAX_FDS
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bcc :-
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lda #ENOMEM
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rts
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; Mark table entry as used
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: lda #$FF
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sta table,x
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; Convert table index to address hibyte
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txa
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asl
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asl
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clc
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adc #>$0800
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; Store address in "memptr"
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ldy #$01
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sta (ptr1),y
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dey
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lda #$00
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sta (ptr1),y
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rts
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iobuf_free:
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; Convert address hibyte to table index
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txa
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sec
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sbc #>$0800
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lsr
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lsr
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; Mark table entry as free
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tax
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lda #$00
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sta table,x
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rts
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; ------------------------------------------------------------------------
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.bss
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table: .res MAX_FDS
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