Developer CD Series 1992 June: ROMin Holiday

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/ Developer CD Series 1992 June: ROMin Holiday / ADC Developer CD (1992-06) (''ROMin Holiday'')_iso / Developer Connection - 06-1992.iso / Development Platforms / Apple II / Essentials / Dynamo 4.2 for GSBug 1.5b10 / rt.a < prev next >

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Text File | 1990-09-21 | 22.7 KB | 1,664 lines | [TEXT/MPS ]

******************************************************* * * * DYNAMO * * * * Apple II 8-bit runtime library routines. * * Copyright (C) 1990 Apple Computer. * * Version 4.1 * * * * Written by Eric Soldan, Apple II DTS * * * ******************************************************* include ':dynamo.includes:sys.equ' import intspace ****************** export rtreset rtreset proc export numtocopy, chrhibiton, chrhibitoff export sign, readendchr, hexpadchr, padhex ldy #255 sty numtocopy sty chrhibitoff iny sty chrhibiton sty sign sty readendchr lda #'0' sta hexpadchr lsr padhex rts numtocopy dc.b 255 ;Will be set back to 255 after ;every string copy or append. chrhibitoff dc.b $FF chrhibiton dc.b 0 sign dc.b 0 readendchr dc.b 0 hexpadchr dc.b '0' padhex dc.b 0 endp *** export hibitchrs hibitchrs proc lda #$80 ;We don't need to set chrhibitoff sta chrhibiton ;because it will either be a $7F rts ;or $FF, and in either case endp ;chrhibiton will turn it on anyway. *** export lowbitchrs lowbitchrs proc asl chrhibiton ;Was a $00 or $80, so this makes it $00. lda #$7F sta chrhibitoff rts endp *** export regchrs regchrs proc asl chrhibiton lda #$FF sta chrhibitoff rts endp *** export rtcout rtcout proc stx @keepx and chrhibitoff ora chrhibiton jsr $FDED ldx @keepx rts @keepx dc.b 0 endp *** export write write proc pla sta @getchr+1 pla sta @getchr+2 txa pha @loop inc @getchr+1 bne @getchr inc @getchr+2 @getchr lda $2000 ;Address modified. beq @exit jsr rtcout jmp @loop @exit pla tax lda @getchr+2 pha lda @getchr+1 pha rts endp *** export writecr writecr proc txa pha lda #13 jsr rtcout pla tax rts endp *** export repeatsp repeatsp proc export repeat lda #' ' repeat sty @count @a jsr rtcout dec @count bne @a rts @count dc.b 0 endp *** export wrcstr wrcstr proc sta @getchr+1 sty @getchr+2 txa pha @getchr lda $2000 ;Address modified. beq @exit jsr rtcout inc @getchr+1 bne @getchr inc @getchr+2 bne @getchr ;Always. @exit pla tax rts endp *** *** *** export signed signed proc sec ror sign rts endp *** export unsigned unsigned proc lsr sign rts endp *** export chngsgn chngsgn proc lda intspace,x eor #$FF clc adc #1 sta intspace,x pha lda intspace+1,x eor #$FF adc #0 sta intspace+1,x tay pla rts endp *** export decoutl decoutl proc import decout ldy #0 jmp decout ;jmp, instead of beq so we can be a lib. endp *** export vdecout vdecout proc export decout lda intspace+1,x tay lda intspace,x decout sta @templ sty @temph lda #'0' sta @temp2 txa pha bit sign bpl @pos tya bpl @pos lda #'-' jsr rtcout lda @templ eor #$FF clc adc #1 sta @templ lda @temph eor #$FF adc #0 sta @temph @pos ldx #4 @a lda #'0' sta @temp @b lda @templ sec sbc @decl,x tay lda @temph sbc @dech,x bcc @c sta @temph sty @templ inc @temp bcs @b @c lda @temp dex bmi @e ;Last digit -- print no matter what. cmp @temp2 beq @a ;Don't print leading 0's. lsr @temp2 ;Inval leading 0 test. jsr rtcout jmp @a @e jsr rtcout pla tax rts @decl dc.b 1 dc.b 10 dc.b 100 dc.b 1000-768 dc.b 10000-9984 @dech dc.b 1>>8 dc.b 10>>8 dc.b 100>>8 dc.b 1000>>8 dc.b 10000>>8 @templ dc.b 0 @temph dc.b 0 @temp dc.b 0 @temp2 dc.b 0 endp *** export hexpad hexpad proc sta hexpadchr lsr padhex rts endp *** export hexnopad hexnopad proc sec ror padhex rts endp *** export hexoutl hexoutl proc import hexout ldy #0 clc jmp hexout+1 ;jmp, instead of beq so we can be a lib. endp *** export vhexout vhexout proc export hexout import hexpadchr lda intspace+1,x tay lda intspace,x hexout sec sta @templ txa pha ldx #3 bcs @aa ldx #1 ldy @templ @aa sty @temph lda padhex sta @padhex lda hexpadchr sta @hexpadchr @loop lda #0 ldy #4 @a asl @templ rol @temph rol a dey bne @a tay bne @b lda @padhex bmi @nopad lda @hexpadchr jsr rtcout jmp @nopad @b jsr @doone lsr @padhex lda #'0' sta @hexpadchr @nopad dex bne @loop lda @temph lsr a lsr a lsr a lsr a tay pla tax @doone lda @hexdigit,y jmp rtcout @hexdigit dc.b '0123456789ABCDEF' @padhex dc.b 0 @hexpadchr dc.b 0 @templ dc.b 0 @temph dc.b 0 endp *** export ldyvar ldyvar proc lda intspace,y pha lda intspace+1,y tay pla rts endp *** export mulconl mulconl proc import mulcon ldy #0 jmp mulcon ;jmp, instead of beq so we can be a lib. endp *** export mulvar mulvar proc export mulcon, mulvall, mulvalh import multiply, setcon jsr ldyvar mulcon pha lda intspace,x sta mulvall lda intspace+1,x sta mulvalh pla jsr multiply jmp setcon mulvall dc.b 0 mulvalh dc.b 0 endp export multiply multiply proc sta @templ sty @temph lda #0 tay @a lsr mulvalh ror mulvall bcc @b clc adc @templ pha tya adc @temph tay pla @b asl @templ rol @temph pha lda mulvalh ora mulvall cmp #1 pla bcs @a rts ;Must exit with carry clear. @templ dc.b 0 @temph dc.b 0 endp export divconl divconl proc import divcon ldy #0 jmp divcon ;jmp, instead of beq so we can be a lib. endp *** export divvar divvar proc export divcon import ldyvar jsr ldyvar divcon sta @templ sty @temph lda #16 sta @temp lda #0 sta @temp2 sta @temp3 @a asl intspace,x rol intspace+1,x rol @temp2 rol @temp3 lda @temp2 sec sbc @templ sta @temp4 lda @temp3 sbc @temph bcc @b sta @temp3 lda @temp4 sta @temp2 inc intspace,x @b dec @temp bne @a lda @temp2 ldy @temp3 rts @templ dc.b 0 @temph dc.b 0 @temp dc.b 0 @temp2 dc.b 0 @temp3 dc.b 0 @temp4 dc.b 0 endp *** export addvar addvar proc export addcon import ldyvar jsr ldyvar addcon pha clc adc intspace,x sta intspace,x tya adc intspace+1,x sta intspace+1,x pla rts endp *** export addconl addconl proc ldy #0 jmp addcon ;jmp, instead of beq so we can be a lib. endp *** export subvar subvar proc export subcon import ldyvar jsr ldyvar subcon pha sta @temp lda intspace,x sec sbc @temp sta intspace,x sty @temp lda intspace+1,x sbc @temp sta intspace+1,x pla rts @temp dc.b 0 endp *** export subconl subconl proc ldy #0 jmp subcon ;jmp, instead of beq so we can be a lib. endp *** export setconl setconl proc export setcon ldy #0 setcon sta intspace,x pha tya sta intspace+1,x pla rts endp *** export setzero setzero proc lda #0 sta intspace+1,x sta intspace,x rts endp *** export seteq seteq proc lda intspace+1,y sta intspace+1,x lda intspace,y sta intspace,x rts endp *** export setvars setvars proc pla sta @gv+1 pla sta @gv+2 txa pha @loop jsr @getval cmp #255 beq @exit tax jsr @getval sta intspace,x jsr @getval sta intspace+1,x bcc @loop ;Always. @exit pla tax lda @gv+2 pha lda @gv+1 pha rts @getval inc @gv+1 bne @gv inc @gv+2 @gv lda $2000 ;Address modified. rts endp *** export xgty xgty proc import vifequal, vifsgneq, xlty0 lda sign bpl @a jsr vifsgneq jmp @b @a jsr vifequal @b bcs @rts jmp xlty0 ;jmp, instead of bcc so we can be a lib. @rts rts endp *** export xlty xlty proc export xlty0 import vifequal, vifsgneq lda sign bpl @a jsr vifsgneq jmp @b @a jsr vifequal @b bcc xltyrts xlty0 lda intspace,x pha lda intspace,y sta intspace,x pla sta intspace,y lda intspace+1,x pha lda intspace+1,y sta intspace+1,x pla sta intspace+1,y xltyrts rts endp *** export ifequal ifequal proc sta @lo+1 sty @hi+1 lda intspace+1,x @hi cmp #0 ;Operand modified. bne @exit lda intspace,x @lo cmp #0 ;Operand modified. @exit php lda @lo+1 plp rts ;eq=eq, cs>=, cc< endp *** export vifequal vifequal proc sta @acc+1 lda intspace+1,x cmp intspace+1,y bne @exit lda intspace,x cmp intspace,y @exit php @acc lda #0 ;Operand modified. plp rts endp *** export ifsgneq ifsgneq proc sta @acc+1 ;Preserve acc. tya cmp #$80 ;Carry set if right side negative. eor intspace+1,x ;See if signs are the same. bmi @exit ;Signs are different -- done. bcs @a ;Variables are negative. lda @acc+1 jmp ifequal ;Variables are positive. @a jsr ifequal beq @rts ;xreg variable is equal. ror a eor #$80 sec ;not equal status. rol a @exit php @acc lda #0 ;Operand modified. plp @rts rts ;eq=eq, cs>=, cc< endp *** export vifsgneq vifsgneq proc sta @acc+1 sty @yreg+1 lda intspace,y ;Load up the variable value and go do it. pha lda intspace+1,y tay pla jsr ifsgneq php @acc lda #0 ;Operand modified. @yreg ldy #0 ;Operand modified. plp rts endp *** export seedrandom seedrandom proc export randomval adc $C02E ;Video counter. pha tya adc $C02E tay bne @a iny @a pla bne @b adc #1 @b sta randomval sty randomval+1 rts randomval dc.w 0 endp *** export calcrandom calcrandom proc stx @keepx ;Keep this so we can restore the xreg. tax ;Use 1 less than limit, so that we can bne @a ;compute the smallest mask possible. This dey ;way, if we are passed $100, we won't @a dex ;compute a mask of $1FF. stx @rndlimit ;The carry was set by cmp #0, so the sty @rndlimit+1 ;sbc #1 is okay. * Figure a mask that is larger than or equal to the rndlimit (minus 1). This will be * used against the calculated randomval before it is compared to the rndlimit. If the * randomval is still too large, then we will get another. ldx #0 lda @rndlimit+1 beq @c ;No hi-byte, so work on low-byte. txa inx @c sec rol a cmp @rndlimit,x bcc @c sta @maskl,x txa eor #1 tax sbc #1 ;Carry set. sta @maskl,x @recalc ldy #19 @d asl randomval rol randomval+1 bcc @e lda randomval eor #$87 sta randomval lda randomval+1 eor #$1D sta randomval+1 @e dey bne @d ldy randomval+1 ldx randomval bne @f dey @f dex tya and @maskh tay txa and @maskl cpy @rndlimit+1 bcc @g bne @recalc cmp @rndlimit bcc @g bne @recalc @g ldx @keepx rts @rndlimit dc.w 0 @keepx dc.b 0 @maskl dc.b 0 @maskh dc.b 0 endp *** *** *** export strval strval proc export midstrval import strinfo, strsign, strvalcount, strvaldigit, strlen, currentstr, nextchr ldy #0 midstrval jsr strinfo sta @getchr+1 stx @getchr+2 lda #0 sta strsign sta strvalcount sta strvaldigit sta @temp sta @temp2 @sign cpy strlen bcs @exit ;Indexed out of string at start. jsr @getchr ;Decimal or hex... cmp #'+' beq @a ;Ignore +'s when figuring sign. cmp #'-' ;Find out if there is an even or odd # of -'s. bne @pos inc strsign @a iny inc strvalcount bcs @sign ;Always. @pos cmp #'$' beq @hex @b cmp #'0' bcc @exit ;Not an int char, so we are done. cmp #'9'+1 bcs @exit ;Not an int char, so we are done. iny inc strvalcount inc strvaldigit sbc #47 ;cclear pha ldx @temp2 ;Multiply by 10. lda @temp asl a rol @temp2 asl a rol @temp2 adc @temp sta @temp txa adc @temp2 asl @temp rol a sta @temp2 pla adc @temp sta @temp bcc @c inc @temp2 @c cpy strlen ;See if we have more characters to look at. bcs @exit ;No more characters to look at. jsr @getchr ;Get the next character. bcc @b ;Always. @exit sty nextchr ;Save next character location. ldx currentstr lda @temp ;Return value in acc,yreg. ldy @temp2 ror strsign ;Should be negative. bcc @rts eor #$FF adc #0 ;cset pha tya eor #$FF adc #0 tay pla @rts rts @getchr lda $2000,y ;Address modified. rts @hex iny inc strvalcount cpy strlen bcs @exit jsr @getchr cmp #'0' bcc @exit cmp #'9'+1 bcc @hexdigit and #$5F cmp #'A' bcc @exit cmp #'Z'+1 bcs @exit sbc #6 ;Carry clear. @hexdigit inc strvaldigit asl @temp rol @temp2 asl @temp rol @temp2 asl @temp rol @temp2 asl @temp rol @temp2 and #$0F ora @temp sta @temp jmp @hex @temp dc.b 0 @temp2 dc.b 0 endp *** export strinfo strinfo proc export currentstr, strlen, maxstrlen, numchrs export strsign, strvalcount, strvaldigit, nextchr import strlens, maxstrlens, strlocs, numtocopy stx currentstr lda strlens,x ;String number in xreg. sta strlen lda maxstrlens,x sta maxstrlen txa asl a tax bcs @a lda strlocs,x pha lda strlocs+1,x tax pla rts @a lda strlocs+$100,x pha lda strlocs+$101,x tax pla rts currentstr dc.b 0 strlen dc.b 0 maxstrlen dc.b 0 numchrs dc.b 0 strsign dc.b 0 strvalcount dc.b 0 strvaldigit dc.b 0 nextchr dc.b 0 endp *** export strptr strptr proc import strlocs stx currentstr pha txa asl a tax pla bcs @a sta strlocs,x tya sta strlocs+1,x bcc @exit @a sta strlocs+$100,x tya sta strlocs+$101,x @exit ldx currentstr rts endp *** export nullstr nullstr proc import strlens lda #0 sta strlens,x rts endp *** export out2str out2str proc export out2stroff import strlens, maxstrlens stx @hook+1 lda cswl ;See what the old output hook is. ldy cswh cmp #<@hook bne @a ;It isn't the string-collection hook. cpy #>@hook beq @rts ;It already is the string-collection hook. @a sta out2stroff+1 sty o2soff+1 lda #<@hook ldy #>@hook sta cswl sty cswh @rts rts @hook ldx #0 ;Modified. (The collection string.) pha ;Keep character. jsr strinfo ;Get the string info and set up the hook. sta @savechr+1 stx @savechr+2 ldx @hook+1 ;The collection string. lda strlens,x cmp maxstrlens,x tay pla ;The character to append. bcs @rts ;String already max length. @savechr sta $2000,y ;Modified. inc strlens,x rts out2stroff lda #0 ;Modified. o2soff ldy #0 ;Modified. beq @rts ;Make sure that out2str was called at least once. sta cswl sty cswh @rts rts endp *** export prstr prstr proc lda #255 ;xreg=str -- write entire string. export prleftstr, prmidstr prleftstr ldy #0 ;xreg=str, acc=numChrs prmidstr cmp #0 beq @exit sta numchrs ;xreg=str, acc=numChrs, yreg=starting chr. jsr strinfo sta @getchr+1 stx @getchr+2 @loop cpy strlen bcs @exit tya pha @getchr lda $2000,y ;Address modified. jsr rtcout pla tay iny dec numchrs bne @loop @exit ldx currentstr rts endp *** export leftstrcpy leftstrcpy proc export strcpy, midstrcpy import numtocopy, copystr sta numtocopy ;Number to copy in acc. strcpy lda #0 ;Copy entire string. midstrcpy clc ;String offset in acc. jmp copystr ;jmp, instead of bcc so we can be a lib. endp *** export leftstrcat leftstrcat proc export strcat, midstrcat, copystr import strlens, strlocs sta numtocopy ;Number to append in acc. strcat lda #0 ;Append entire string. midstrcat sec ;String offset in acc. copystr pha ;Keep source offset. php ;Keep copy or append status. jsr strinfo sta @dst+1 stx @dst+2 lda strlens,y sta @srcstrlen tya asl a tay bcs @a lda strlocs,y sta @src+1 lda strlocs+1,y sta @src+2 bcc @b @a lda strlocs+$100,y sta @src+1 lda strlocs+$101,y sta @src+2 @b ldx #0 plp ;Get copy or append status. bcc @c ;Copy status. ldx strlen ;Append status. @c pla tay ;Source offset. @loop cpy @srcstrlen bcs @exit cpx maxstrlen bcs @exit @src lda $2000,y ;Address modified. @dst sta $2000,x ;Address modified. inx iny dec numtocopy bne @loop @exit lda #255 ;Set it back for next midstr operation. sta numtocopy ;The next one may only have 3 parameters. txa ;xreg has destination string length. ldx currentstr sta strlens,x rts @srcstrlen dc.b 0 endp *** export litstr litstr proc import strlens pla sta @getchr+1 pla sta @getchr+2 jsr strinfo sta @putchr+1 stx @putchr+2 ldy #0 @loop inc @getchr+1 bne @getchr inc @getchr+2 @getchr lda $2000 ;Address modified. beq @exit cpy maxstrlen bcs @loop @putchr sta $2000,y iny bne @loop @exit lda @getchr+2 pha lda @getchr+1 pha ldx currentstr tya sta strlens,x rts endp *** export strchr strchr proc tay jsr strinfo sta @getchr+1 stx @getchr+2 @getchr lda $2000,y ldx currentstr rts endp *** export strloc strloc proc jsr strinfo pha txa tay ldx currentstr pla rts endp *** *** *** export restore restore proc import getdatabyte sta getdatabyte+1 sty getdatabyte+2 rts endp *** export getdatabyte getdatabyte proc lda $2000 inc getdatabyte+1 bne @rts inc getdatabyte+2 @rts rts endp *** export readint readint proc jsr getdatabyte sta intspace,x pha jsr getdatabyte sta intspace+1,x tay pla rts endp *** export readstr readstr proc import strlens jsr strinfo sta @putchr+1 stx @putchr+2 ldy #0 @loop jsr getdatabyte cmp readendchr beq @exit cpy maxstrlen bcs @loop @putchr sta $2000,y iny bne @loop @exit ldx currentstr tya sta strlens,x rts endp *** export readend readend proc sta readendchr rts endp *** *** *** export arraybase arraybase proc export arrayloc1, arrayloc2, arrayloc3 export arrayloc0l, arrayloc0h export arrayloc1l, arrayloc1h export arrayloc2l, arrayloc2h export arrayloc3l, arrayloc3h export dim0sizel, dim0sizeh export dim1sizel, dim1sizeh export dim2sizel, dim2sizeh export dim3sizel, dim3sizeh sta arrayloc0l ;Save base address. sty arrayloc0h jsr arrayloc1 ;Set other addresses to base, as well. pla ;Use return address to access array dimensions. sta @gb+1 pla sta @gb+2 txa pha ldx #0 @loop jsr @getb ;Get lo-byte. sta dim0sizel,x ;This is safe, since we have an overflow byte below. php ;Save status of lo-byte. jsr @getb ;Get hi-byte. plp ;Status of lo-byte. bne @a ;This isn't the NULL word indicating the end. tay ;Get status of hi-byte. beq @loop2 ;This is the NULL word indicating the end. @a sta dim0sizeh,x ;This is safe, since we have an overflow word below. inx inx bne @loop ;Always. @loop2 lda dim0sizel-2,x ;Save the last size for the rest of the dimensions. sta dim0sizel,x inx cpx #8 bcc @loop2 pla tax lda @gb+2 pha lda @gb+1 pha rts @getb inc @gb+1 bne @gb inc @gb+2 @gb lda $2000 ;Address modified. rts arrayloc1 sta arrayloc1l sty arrayloc1h arrayloc2 sta arrayloc2l sty arrayloc2h arrayloc3 sta arrayloc3l sty arrayloc3h sta aptr sty aptr+1 rts arrayloc0l dc.b 0 arrayloc0h dc.b 0 arrayloc1l dc.b 0 arrayloc1h dc.b 0 arrayloc2l dc.b 0 arrayloc2h dc.b 0 arrayloc3l dc.b 0 arrayloc3h dc.b 0 dim0sizel dc.b 0 ;dim0 is the element size. dim0sizeh dc.b 0 dim1sizel dc.b 0 dim1sizeh dc.b 0 dim2sizel dc.b 0 dim2sizeh dc.b 0 dim3sizel dc.b 0 dim3sizeh dc.b 0 dc.b 0 ;Overflow -- simplifies loop save/test. endp *** export varyindx1 varyindx1 proc export arrayindx1, arraylindx1 lda intspace,y pha lda intspace+1,y tay pla arrayindx1 sta mulvall sty mulvalh lda dim1sizel ldy dim1sizeh jsr multiply clc adc arrayloc0l pha tya adc arrayloc0h tay pla jmp arrayloc1 arraylindx1 ldy #0 ;Low-byte-only index entry point. beq arrayindx1 endp *** export varyindx2 varyindx2 proc export arrayindx2, arraylindx2 lda intspace,y pha lda intspace+1,y tay pla arrayindx2 sta mulvall sty mulvalh lda dim2sizel ldy dim2sizeh jsr multiply clc adc arrayloc1l pha tya adc arrayloc1h tay pla jmp arrayloc2 arraylindx2 ldy #0 ;Low-byte-only index entry point. beq arrayindx2 endp *** export varyindx3 varyindx3 proc export arrayindx3, arraylindx3 lda intspace,y pha lda intspace+1,y tay pla arrayindx3 sta mulvall sty mulvalh lda dim3sizel ldy dim3sizeh jsr multiply clc adc arrayloc2l pha tya adc arrayloc2h tay pla jmp arrayloc3 arraylindx3 ldy #0 ;Low-byte-only index entry point. beq arrayindx3 endp *** export vgetele vgetele proc export getelel, getele, getele0 import floatspace lda intspace,y pha lda intspace+1,y tay pla dc.b $2C ;Skip the ldy #0 below. getelel ldy #0 getele sta mulvall sty mulvalh lda dim0sizel ldy dim0sizeh jsr multiply adc arrayloc3l ;multiply clears the carry. sta aptr tya adc arrayloc3h sta aptr+1 getele0 lda dim0sizel ;See which: byte,int,float. ldy #1 ;Efficient to set yreg here for byte,int. cmp #2 beq @int bcs @float @byte lda #0 beq @a @int lda (aptr),y @a sta intspace+1,x dey lda (aptr),y sta intspace,x rts @float txa pha dey @b lda (aptr),y iny sta floatspace,x inx cpy #5 bcc @b pla tax rts endp *** export getnextele getnextele proc lda aptr clc adc dim0sizel sta aptr bcc @a inc aptr+1 @a jmp getele0 endp *** export vputele vputele proc export putelel, putele, putele0 import floatspace lda intspace,y pha lda intspace+1,y tay pla dc.b $2C ;Skip the ldy #0 below. putelel ldy #0 putele sta mulvall sty mulvalh lda dim0sizel ldy dim0sizeh jsr multiply adc arrayloc3l ;multiply clears the carry. sta aptr tya adc arrayloc3h sta aptr+1 putele0 lda dim0sizel ;See which: byte,int,float. ldy #0 ;Efficient to set yreg here for byte,int. cmp #2 beq @int bcs @float @int lda intspace,x sta (aptr),y bcc @rts ;Element size is byte. lda intspace+1,x iny sta (aptr),y @rts rts @float txa pha @a lda floatspace,x inx sta (aptr),y iny cpy #5 bcc @a pla tax rts endp *** export putnextele putnextele proc lda aptr clc adc dim0sizel sta aptr bcc @a inc aptr+1 @a jmp putele0 endp *** export deref deref PROC sta @getbyte+1 sty @getbyte+2 jsr @getbyte ;Get low-byte. tya inc @getbyte+1 bne @getbyte inc @getbyte+2 @getbyte ldy $2000 ;Address modified. rts endp *** export aderefz aderefz PROC export aderef lda $2000 ;Address modified. inc aderefz+1 bne @rts inc aderefz+2 @rts rts aderef sta aderefz+1 jsr aderefz ;Get low-byte. pha jsr aderefz sta aderefz+2 pla rts endp *** export yderefz yderefz PROC export yderef ldy $2000 ;Address modified. inc yderefz+1 bne @rts inc yderefz+2 @rts rts yderef sty yderefz+1 jsr yderefz ;Get low-byte. sty @lo jsr yderefz sty yderefz+2 ldy @lo rts @lo dc.b 0 endp *** export vderef ;x-reg variable deref. vderef PROC pha lda intspace,x sta @getbyte+1 lda intspace+1,x sta @getbyte+2 jsr @getbyte ;Get low-byte. sta intspace,x inc @getbyte+1 bne @a inc @getbyte+2 @a jsr @getbyte sta intspace+1,x pla rts @getbyte lda $2000 ;Address modified. rts endp end