diff --git a/graphics/dhgr_viewer/dhires_main.s b/graphics/dhgr_viewer/dhires_main.s new file mode 100644 index 00000000..ce73d848 --- /dev/null +++ b/graphics/dhgr_viewer/dhires_main.s @@ -0,0 +1,132 @@ +; VMW Productions DHIRES/ZX02 image viewer +; +; by deater (Vince Weaver) + +; todo help menu, timed slideshow mode +; move to being a bootsector + +.include "zp.inc" +.include "hardware.inc" + +WHICH = $E0 + +hires_start: + + ;=================== + ; Init RTS disk code + ;=================== + + jsr rts_init + + ;=================== + ; set graphics mode + ;=================== + jsr HOME + + bit SET_GR + bit HIRES + bit FULLGR + sta AN3 ; set double hires + sta EIGHTYCOLON ; 80 column + sta SET80COL ; 80 store + + bit PAGE1 ; start in page1 + + lda #0 + sta WHICH + + ;=================== + ; Load graphics + ;=================== +load_loop: + + ;============================= + + ldx WHICH + + lda bin_filenames_low,X + sta OUTL + lda bin_filenames_high,X + sta OUTH + + lda aux_filenames_low,X + sta INL + lda aux_filenames_high,X + sta INH + + jsr load_image + +wait_until_keypress: + lda KEYPRESS ; 4 + bpl wait_until_keypress ; 3 + bit KEYRESET ; clear the keyboard buffer + + cmp #$88 ; left button + bne inc_which + + dec WHICH + bpl which_ok + + ldx #(MAX_FILES-1) + bne store_which ; bra + +inc_which: + inc WHICH + ldx WHICH + cpx #MAX_FILES + bcc which_ok ; blt + + ldx #0 +store_which: + stx WHICH + +which_ok: + jmp load_loop + + + ;========================== + ; Load Image + ;=========================== + +load_image: + bit PAGE1 + + jsr opendir_filename ; open and read entire file into memory + + lda #<$A000 + sta zx_src_l+1 + + lda #>$A000 + sta zx_src_h+1 + + lda #$20 + + jsr zx02_full_decomp + + ; auxiliary part + + lda INL + sta OUTL + lda INH + sta OUTH + + jsr opendir_filename ; open and read entire file into memory + + bit PAGE2 + + lda #<$A000 + sta zx_src_l+1 + + lda #>$A000 + sta zx_src_h+1 + + lda #$20 + + jsr zx02_full_decomp + + rts + + .include "zx02_optim.s" + .include "rts.s" + +; diff --git a/graphics/dhgr_viewer/hardware.inc b/graphics/dhgr_viewer/hardware.inc new file mode 100644 index 00000000..5edffbe2 --- /dev/null +++ b/graphics/dhgr_viewer/hardware.inc @@ -0,0 +1,84 @@ +;; HARDWARE LOCATIONS + +KEYPRESS = $C000 +KEYRESET = $C010 + +;; SOFT SWITCHES +CLR80COL = $C000 ; PAGE1/PAGE2 normal +SET80COL = $C001 ; PAGE1/PAGE2 switches PAGE0 in Aux instead +EIGHTYCOLOFF = $C00C +EIGHTYCOLON = $C00D +SPEAKER = $C030 +SET_GR = $C050 +SET_TEXT = $C051 +FULLGR = $C052 +TEXTGR = $C053 +PAGE1 = $C054 +PAGE2 = $C055 +LORES = $C056 ; Enable LORES graphics +HIRES = $C057 ; Enable HIRES graphics +AN3 = $C05E ; Annunciator 3 + +PADDLE_BUTTON0 = $C061 +PADDL0 = $C064 +PTRIG = $C070 + +;; BASIC ROUTINES + +NORMAL = $F273 + +;; MONITOR ROUTINES + +HLINE = $F819 ;; HLINE Y,$2C at A +VLINE = $F828 ;; VLINE A,$2D at Y +CLRSCR = $F832 ;; Clear low-res screen +CLRTOP = $F836 ;; clear only top of low-res screen +SETCOL = $F864 ;; COLOR=A +TEXT = $FB36 +TABV = $FB5B ;; VTAB to A +BASCALC = $FBC1 ;; +VTAB = $FC22 ;; VTAB to CV +HOME = $FC58 ;; Clear the text screen +WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us +SETINV = $FE80 ;; INVERSE +SETNORM = $FE84 ;; NORMAL +COUT = $FDED ;; output A to screen +COUT1 = $FDF0 ;; output A to screen + + + + + + +COLOR_BLACK = 0 +COLOR_RED = 1 +COLOR_DARKBLUE = 2 +COLOR_PURPLE = 3 +COLOR_DARKGREEN = 4 +COLOR_GREY = 5 +COLOR_MEDIUMBLUE = 6 +COLOR_LIGHTBLUE = 7 +COLOR_BROWN = 8 +COLOR_ORANGE = 9 +COLOR_GREY2 = 10 +COLOR_PINK = 11 +COLOR_LIGHTGREEN = 12 +COLOR_YELLOW = 13 +COLOR_AQUA = 14 +COLOR_WHITE = 15 + +COLOR_BOTH_BLACK = $00 +COLOR_BOTH_RED = $11 +COLOR_BOTH_DARKBLUE = $22 +COLOR_BOTH_DARKGREEN = $44 +COLOR_BOTH_GREY = $55 +COLOR_BOTH_MEDIUMBLUE = $66 +COLOR_BOTH_LIGHTBLUE = $77 +COLOR_BOTH_BROWN = $88 +COLOR_BOTH_ORANGE = $99 +COLOR_BOTH_PINK = $BB +COLOR_BOTH_LIGHTGREEN = $CC +COLOR_BOTH_YELLOW = $DD +COLOR_BOTH_AQUA = $EE +COLOR_BOTH_WHITE = $FF + diff --git a/graphics/dhgr_viewer/hello.bas b/graphics/dhgr_viewer/hello.bas new file mode 100644 index 00000000..b124c96b --- /dev/null +++ b/graphics/dhgr_viewer/hello.bas @@ -0,0 +1,2 @@ + 5 HOME + 105 PRINT CHR$ (4)"BRUN DHIRES" diff --git a/graphics/dhgr_viewer/rts.s b/graphics/dhgr_viewer/rts.s new file mode 100644 index 00000000..4aa41375 --- /dev/null +++ b/graphics/dhgr_viewer/rts.s @@ -0,0 +1,557 @@ +; read any file slot 6 version +; based on FASTLD6 and RTS copyright (c) Peter Ferrie 2011-2013,2018 + +; modified to assembled with ca65 -- vmw +; added code to patch it to run from current disk slot -- vmw + +; USAGE: +; file to load in namlo:namhi +; Loads file contents to addr from filesystem +; also stores filesize in ldsizel:ldsizeh + + dirbuf = $900 + ; note, don't put this immediately below + ; the value being read as destaddr-4 + ; is temporarily overwritten during read + ; process + + ;====================== + + + +; filename to open is 30-character Apple text: +filename: + .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0 + .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0 + .byte $A0,$A0,$A0,$A0,$A0,$A0,$A0,$A0 + .byte $A0,$A0,$A0,$A0,$A0,$A0 + +;======================================================= +;======================================================= +;======================================================= + ;unhook DOS and build nibble table +rts_init: + ; patch to use current drive + + ; locate input paramater list + jsr $3E3 + ; result is in A:Y + sta $FF + sty $FE + ldy #1 + lda ($FE),y + + ; list+1 should have slot<<8 + + + ora #$80 ; add in $80 + + ; c0e0 + sta mlsmc06+1 + + ; c0e8 + clc + adc #8 + sta mlsmc02+1 + + ; c0e9 + clc + adc #1 + sta mlsmc01+1 + + ; c0ec + clc + adc #3 + sta mlsmc03+1 + sta mlsmc04+1 + sta mlsmc05+1 + + jsr $fe93 ; clear COUT + jsr $fe89 ; clear KEYIN + + ;======================== + ; Create nibble table + ; Note: the table starts 16 bytes in, and is sparse + ; so it doesn't entirely look like the DOS33 table at + + ldy #0 + ldx #3 +L1: stx $3c ; store tempx (3?) + txa ; a=x (a=3) + asl ; a*=2 (a=6) + bit $3c ; a&tempx, set N/V (a=6) + beq L3 ; if 0, skip to L3 + ora $3c ; a|=tempx (a=7) + eor #$ff ; a=~a (a=f8) + and #$7e ; a&=0x7e 0111 1110 (a=78) +L2: bcs L3 ; this set way back at asl?? + lsr ; a>>1 a=3c c=0 + ; a=1e c=0 + ; a=0f c=0 + ; a=07 c=1 + bne L2 ; if a!=0 goto l2 + tya ; if a==0, a=y + sta nibtbl, x ; write out to table + iny ; increment y +L3: inx ; increment x x=4, a=0f + bpl L1 ; loop while high bit not set + + rts + + +;======================================================= +;======================================================= +;======================================================= + + ; filename in OUTL:OUTH + +opendir_filename: + + ; clear out the filename with $A0 (space) + + lda #filename + sta namhi + + ldy #29 +wipe_filename_loop: + lda #$A0 + sta (namlo),Y + dey + bpl wipe_filename_loop + + ldy #0 +copy_filename_loop: + lda (OUTL),Y + beq copy_filename_done + sta (namlo),Y + iny + bne copy_filename_loop + +copy_filename_done: + + ; fallthrough + +;======================================================= +;======================================================= +;======================================================= + + ;=========================== + ; opendir + ;=========================== + + ; turn on drive and read volume table of contents +opendir: +mlsmc01:lda $c0e9 ; turn slot#6 drive on + ldx #0 + stx adrlo ; zero out adrlo + stx secsize ; zero out secsize + lda #$11 ; a=$11 (VTOC) + jsr readdirsec +firstent: + + lda dirbuf+1 + + ; lock if entry not found +entry_not_found: + beq entry_not_found + + ; read directory sector + + ldx dirbuf+2 + jsr seekread1 + ldy #7 ;number of directory entries in a sector + ldx #$2b ;offset of filename in directory entry +nextent: + tya + pha ; was **phy** + txa + pha ; was **phx** + ldy #$1d + + ; match name backwards (slower but smaller) + +L4: + lda (namlo), y + cmp dirbuf, x + beq foundname + pla + + ; move to next directory in this block, if possible + + clc + adc #$23 + tax + pla + tay ; was **ply** + dey + bne nextent + beq firstent ; was **bra** + +foundname: + dex + dey + bpl L4 + pla + tay ; was **ply** + pla + + ; read track/sector list + + lda dirbuf-32, y + ldx dirbuf-31, y + jsr seekread1 + + ; read load offset and length info only, initially + + lda #filbuf + jsr seekread + + ; reduce load offset by 4, to account for offset and length + + sec + lda filbuf + sbc #4 + sta adrlo + + lda filbuf+1 + sbc #0 + sta adrhi + + ; save on stack bytes that will be overwritten by extra read + + ldy #3 +L5: + lda (adrlo), y + pha + dey + bpl L5 + + lda adrhi + pha + lda adrlo + pha + + ; increase load size by 4, to account for offst and length + + lda filbuf+2 + sta ldsizel ; store out raw size + + adc #3 + sta sizelo + sta secsize + + lda filbuf+3 + sta ldsizeh ; store out raw size + + adc #0 + sta sizehi + sta ldsizeh + beq readfirst + lda #0 ; was **stz secsize** + sta secsize + +readfirst: + ldy #$0c + + ; read a file sector + +readnext: + tya + pha + lda dirbuf, y ; A = track + ldx dirbuf+1, y ; x = sector + jsr seekread1 + pla + tay + + ; if low count is non-zero then we are done + ; (can happen only for partial last block) + + lda secsize + bne readdone + + ; continue if more than $100 bytes left + + dec sizehi + bne L6 + + ; set read size to min(length, $100) + + lda sizelo + beq readdone + sta secsize +L6: + inc adrhi + iny + iny + bne readnext + + ; save current address for after t/s read + + lda adrhi + pha + lda adrlo + pha + lda #0 + sta adrlo ; was **stz adrlo** + + ; read next track/sector sector + + lda dirbuf+1 + ldx dirbuf+2 + jsr readdirsec + clc + + ; restore current address +readdone: + pla +; sta adrhi +; pla + sta adrlo ; code originally had this backwards + pla + sta adrhi + bcc readfirst + +mlsmc02:lda $c0e8 + + ; restore from stack bytes that were overwritten by extra read + + ldx #3 + ldy #0 +L7: + pla + sta (adrlo), y + iny + dex + bpl L7 + rts + + + ;====================== + ; readdirsec + ;====================== + ; a = track? + ; x = sector? +readdirsec: + ldy #>dirbuf +seekread: + sty adrhi +seekread1: + sta phase + lda sectbl, x + sta reqsec + jsr readadr + + ; if track does not match, then seek + + cpx phase + beq checksec + jsr seek + + + ;========================================= + ; re merge in with qkumba's recent changes + ; to fix seek problem? + ;========================================= + + ; [re-]read sector + +re_read_addr: + jsr readadr +checksec: + cmp reqsec + bne re_read_addr + + ;========================= + ; read sector data + ;========================= + +readdata: + jsr readd5aa + eor #$ad ; zero A if match + bne re_read_addr + +L12: +mlsmc03:ldx $c0ec ; read until valid data (high bit set) + bpl L12 + eor nibtbl-$80, x + sta bit2tbl-$aa, y + iny + bne L12 +L13: +mlsmc04:ldx $c0ec ; read until valid data (high bit set) + bpl L13 + eor nibtbl-$80, x + sta (adrlo), y ; the real address + iny + cpy secsize + bne L13 + ldy #0 +L14: + ldx #$a9 +L15: + inx + beq L14 + lda (adrlo), y + lsr bit2tbl-$aa, x + rol + lsr bit2tbl-$aa, x + rol + sta (adrlo), y + iny + cpy secsize + bne L15 + rts + + ; no tricks here, just the regular stuff + + ;======================= + ; readaddr -- read the address field + ;======================= + ; Find address field, put track in cutrk, sector in tmpsec + +readadr: + jsr readd5aa + cmp #$96 + bne readadr + ldy #3 ; three? + ; first read volume/volume + ; then track/track + ; then sector/sector? +adr_read_two_bytes: + tax + jsr readnib + rol + sta tmpsec + jsr readnib + and tmpsec + dey + bne adr_read_two_bytes + rts + + ;======================== + ; make sure we see the $D5 $AA pattern + +readd5aa: +L16: + jsr readnib +L17: + cmp #$d5 + bne L16 + jsr readnib + cmp #$aa + bne L17 + tay ; we need Y=#$AA later + +readnib: +mlsmc05:lda $c0ec ; read until valid (high bit set) + bpl readnib + +seekret: + rts + + ;===================== + ; SEEK + ;===================== + ; current track in X? + ; desired track in phase + +seek: + ldy #0 + sty step + asl phase ; multiply by two + txa ; current track? + asl ; mul by two +copy_cur: + tax + sta tmptrk + sec + sbc phase + beq L22 + bcs L18 + eor #$ff + inx + bcc L19 +L18: + sbc #1 + dex +L19: + cmp step + bcc L20 + lda step +L20: + cmp #8 + bcs L21 + tay + sec +L21: + txa + pha + ldx step1, y +L22: + php + bne L24 +L23: + clc + lda tmptrk + ldx step2, y +L24: + stx tmpsec + and #3 + rol + tax + lsr +mlsmc06:lda $c0e0, x +L25: + ldx #$12 +L26: + dex + bpl L26 + dec tmpsec + bne L25 + bcs L23 + plp + beq seekret + pla + inc step + bne copy_cur + + +step1: .byte $01, $30, $28, $24, $20, $1e, $1d, $1c +step2: .byte $70, $2c, $26, $22, $1f, $1e, $1d, $1c + +sectbl: .byte $00,$0d,$0b,$09,$07,$05,$03,$01,$0e,$0c,$0a,$08,$06,$04,$02,$0f + + +; From $BA96 of DOS33 +nibtbl: .res 128 ; = * +; .byte $00,$01,$98,$99,$02,$03,$9C,$04 ; $BA96 ; 00 +; .byte $05,$06,$A0,$A1,$A2,$A4,$A4,$A5 ; $BA9E ; 08 +; .byte $07,$08,$A8,$A9,$AA,$09,$0A,$0B ; $BAA6 ; 10 +; .byte $0C,$0D,$B0,$B1,$0E,$0F,$10,$11 ; $BAAE ; 18 +; .byte $12,$13,$B8,$14,$15,$16,$17,$18 ; $BAB6 ; 20 +; .byte $19,$1A,$C0,$C1,$C2,$C3,$C4,$C5 ; $BABE ; 28 +; .byte $C6,$C7,$C8,$C9,$CA,$1B,$CC,$1C ; $BAC6 ; 30 +; .byte $1D,$1E,$D0,$D1,$D2,$1E,$D4,$D5 ; $BACE ; 38 +; .byte $20,$21,$D8,$22,$23,$24,$25,$26 ; $BAD6 ; 40 +; .byte $27,$28,$E0,$E1,$E2,$E3,$E4,$29 ; $BADE ; 48 +; .byte $2A,$2B,$E8,$2C,$2D,$2E,$2F,$30 ; $BAE6 ; 50 +; .byte $31,$32,$F0,$F1,$33,$34,$35,$36 ; $BAEE ; 58 +; .byte $37,$38,$F8,$39,$3A,$3B,$3C,$3D ; $BAF6 ; 60 +; .byte $3E,$3F,$13,$00,$01,$02,$01,$00 ; $BAFE ; 68 +; .byte $00,$00,$00,$00,$00,$00,$00,$00 +; .byte $00,$00,$00,$00,$00,$00,$00,$00 + + +bit2tbl: .res 86 ; = nibtbl+128 +filbuf: .res 4 ; = bit2tbl+86 + ;dataend = filbuf+4 + diff --git a/graphics/dhgr_viewer/zp.inc b/graphics/dhgr_viewer/zp.inc new file mode 100644 index 00000000..7a059406 --- /dev/null +++ b/graphics/dhgr_viewer/zp.inc @@ -0,0 +1,182 @@ +;; Zero Page + + +;; ZX0 addresses + +ZX0_src = $00 +ZX0_dst = $02 +offset = $04 +bitr = $06 +pntr = $07 +WHICH_LOAD = $09 +CURRENT_DISK = $0A + +;; Zero page monitor routines addresses + +WNDLFT = $20 +WNDWDTH = $21 +WNDTOP = $22 +WNDBTM = $23 +CH = $24 +CV = $25 +GBASL = $26 +GBASH = $27 +BASL = $28 +BASH = $29 +H2 = $2C +V2 = $2D +MASK = $2E +COLOR = $30 + ;INVFLG = $32 + +; dos33 zero page = 26-2f, 35-38, 3e 3f 40-4d +; overlap applesoft 67-6a,6f,70,af,b0,ca-cd,d8 + + +; DOS33: Confirmed kills $68 + +RWTSL = $60 +RWTSH = $61 +DOSBUFL = $62 +DOSBUFH = $63 +FILEML = $64 +FILEMH = $65 + + +FRAME = $60 +FRAMEH = $61 +WAITING = $62 +LETTERL = $63 +LETTERH = $64 +LETTERX = $65 +LETTERY = $66 +LETTERD = $67 +LETTER = $68 +BLARGH = $69 + + ;FACTOR_I = $66 + ;FACTOR_F = $67 + ;DX_I = $68 + ;DX_F = $69 + ;SPACEX_I = $6A + ;SPACEX_F = $6B + ;CX_I = $6C + ;CX_F = $6D + ;DY_I = $6E + ;DY_F = $6F + + +ZPOS = $78 + +REGISTER_DUMP = $70 +A_FINE_TONE = $70 +A_COARSE_TONE = $71 +B_FINE_TONE = $72 +B_COARSE_TONE = $73 +C_FINE_TONE = $74 +C_COARSE_TONE = $75 +NOISE = $76 +ENABLE = $77 +A_VOLUME = $78 +B_VOLUME = $79 +C_VOLUME = $7A +ENVELOPE_FINE = $7B +ENVELOPE_COARSE = $7C +ENVELOPE_SHAPE = $7D + + +COPY_OFFSET = $7E +DECODER_STATE = $7F + + +REGISTER_DUMP2 = $80 +A_FINE_TONE2 = $80 +A_COARSE_TONE2 = $81 +B_FINE_TONE2 = $82 +B_COARSE_TONE2 = $83 +C_FINE_TONE2 = $84 +C_COARSE_TONE2 = $85 +NOISE2 = $86 +ENABLE2 = $87 +A_VOLUME2 = $88 +B_VOLUME2 = $89 +C_VOLUME2 = $8A +ENVELOPE_FINE2 = $8B +ENVELOPE_COARS2 = $8C +ENVELOPE_SHAPE2 = $8D +LYRICSL = $8E +LYRICSH = $8F + +FRAME_COUNT = $90 +MB_VALUE = $91 +MB_ADDRL = $91 +MB_ADDRH = $92 +DONE_PLAYING = $93 +MB_CHUNK_OFFSET = $94 +MB_FRAME = $94 +MB_PATTERN = $95 +CHUNKSIZE = $95 +LZ4_DONE = $96 +DECODE_ERROR = $97 +COPY_TIME = $98 +DECOMPRESS_TIME = $99 +TIME_TAKEN = $9A +LYRICS_ACTIVE = $9B +;FORTYCOL = $9C +CURSOR = $9D + +; More zero-page addresses +; we try not to conflict with anything DOS, MONITOR or BASIC related + + ;COLOR1 = $E0 + ;COLOR2 = $E1 + ;MATCH = $E2 +XX = $E3 +YY = $E4 +HGR_COLOR = $E4 + ;SHIPY = $E4 + ;YADD = $E5 + ;LOOP = $E6 + ;MEMPTRL = $E7 + ;MEMPTRH = $E8 + ;NAMEL = $E9 + ;NAMEH = $EA + ;NAMEX = $EB + ;CHAR = $EC + +INL = $EE +INH = $EF + + + +OUTL = $FE +OUTH = $FF + + + + + + +; read any file slot 6 version +; based on FASTLD6 and RTS copyright (c) Peter Ferrie 2011-2013,2018 + +; modified to assembled with ca64 -- vmw +; added code to patch it to run from current disk slot -- vmw + + + adrlo = $26 ; constant from boot prom + adrhi = $27 ; constant from boot prom + tmpsec = $3c ; constant from boot prom + reqsec = $3d ; constant from boot prom + sizelo = $44 + sizehi = $45 + secsize = $46 + + ldsizel = $f0 + ldsizeh = $f1 + namlo = $fb + namhi = $fc + step = $fd ; state for stepper motor + tmptrk = $fe ; temporary copy of current track + phase = $ff ; current phase for /seek + diff --git a/graphics/dhgr_viewer/zx02_optim.s b/graphics/dhgr_viewer/zx02_optim.s new file mode 100644 index 00000000..5eebc2e0 --- /dev/null +++ b/graphics/dhgr_viewer/zx02_optim.s @@ -0,0 +1,159 @@ +; De-compressor for ZX02 files +; ---------------------------- +; +; Decompress ZX02 data (6502 optimized format), optimized for speed and size +; 138 bytes code, 58.0 cycles/byte in test file. +; +; Compress with: +; zx02 input.bin output.zx0 +; +; (c) 2022 DMSC +; Code under MIT license, see LICENSE file. + + +;ZP=$80 + +;offset = ZP+0 +;ZX0_src = ZP+2 +;ZX0_dst = ZP+4 +;bitr = ZP+6 +;pntr = ZP+7 + + ; Initial values for offset, source, destination and bitr +;zx0_ini_block: +; .byte $00, $00, comp_data, out_addr, $80 + +;-------------------------------------------------- +; Decompress ZX0 data (6502 optimized format) + +zx02_full_decomp: +; ; Get initialization block +; ldy #7 +; +;copy_init: lda zx0_ini_block-1, y +; sta offset-1, y +; dey +; bne copy_init + + + sta ZX0_dst+1 ; page to output to in A +zx_src_l: + ldy #$dd + sty ZX0_src +zx_src_h: + ldy #$dd + sty ZX0_src+1 + ldy #$80 + sty bitr + ldy #0 + sty offset + sty offset+1 + sty ZX0_dst ; always on even page + +; Decode literal: Ccopy next N bytes from compressed file +; Elias(length) byte[1] byte[2] ... byte[N] +decode_literal: + jsr get_elias + +cop0: lda (ZX0_src), y + inc ZX0_src + bne plus1 + inc ZX0_src+1 +plus1: sta (ZX0_dst),y + inc ZX0_dst + bne plus2 + inc ZX0_dst+1 +plus2: dex + bne cop0 + + asl bitr + bcs dzx0s_new_offset + +; Copy from last offset (repeat N bytes from last offset) +; Elias(length) + jsr get_elias +dzx0s_copy: + lda ZX0_dst + sbc offset ; C=0 from get_elias + sta pntr + lda ZX0_dst+1 + sbc offset+1 + sta pntr+1 + +cop1: + lda (pntr), y + inc pntr + bne plus3 + inc pntr+1 +plus3: sta (ZX0_dst),y + inc ZX0_dst + bne plus4 + inc ZX0_dst+1 +plus4: dex + bne cop1 + + asl bitr + bcc decode_literal + +; Copy from new offset (repeat N bytes from new offset) +; Elias(MSB(offset)) LSB(offset) Elias(length-1) +dzx0s_new_offset: + ; Read elias code for high part of offset + jsr get_elias + beq exit ; Read a 0, signals the end + ; Decrease and divide by 2 + dex + txa + lsr ; @ + sta offset+1 + + ; Get low part of offset, a literal 7 bits + lda (ZX0_src), y + inc ZX0_src + bne plus5 + inc ZX0_src+1 +plus5: + ; Divide by 2 + ror ; @ + sta offset + + ; And get the copy length. + ; Start elias reading with the bit already in carry: + ldx #1 + jsr elias_skip1 + + inx + bcc dzx0s_copy + +; Read an elias-gamma interlaced code. +; ------------------------------------ +get_elias: + ; Initialize return value to #1 + ldx #1 + bne elias_start + +elias_get: ; Read next data bit to result + asl bitr + rol ; @ + tax + +elias_start: + ; Get one bit + asl bitr + bne elias_skip1 + + ; Read new bit from stream + lda (ZX0_src), y + inc ZX0_src + bne plus6 + inc ZX0_src+1 +plus6: ;sec ; not needed, C=1 guaranteed from last bit + rol ;@ + sta bitr + +elias_skip1: + txa + bcs elias_get + ; Got ending bit, stop reading +exit: + rts