As a rule Gazette type-ins weren't generally multiloads and Ultrafont+ as published was already in one file. However, I ran across a nice version (no idea who did this) with a BASIC stub that printed the keystroke commands, which I thought was a handy addition. My own Perl-based BASIC cross-linker can one-part a BASIC program and any number of additional modules, so I took the original BASIC loader and made the following changes and deletions:
10
120 print "{Sr} press a key for ultrafont+ "
255 poke198,.:wait198,1:geta$
260
300 sys49152
310 print"{Sq}'run' for help screen and ultrafont+"
320
Since my linker correctly resets the end-of-BASIC pointer (recall that LOADing any program file, even a non-BASIC program outside of the normal BASIC text range, will set this pointer), there's no need to NEW everything out like the old BASIC stub did to avoid hitting spurious out-of-memory errors. Plus, doing so keeps the instructions in memory so you can just re-RUN it.
The next step was to make it respect the default device number. Ultrafont+ supports both cassette and disk, but it only supports disk device 8. In both Power64 and VICE, I usually reserve device 8 for any mounted D64s and 9 for the development filesystem, and I'd prefer that files I save and load go directly to the filesystem for cross-manipulation, linking, etc.; ideally it should save and load from the device that was most recently accessed. That kind of patch is ordinarily trivial and usually you can find what needs to be changed by looking for any Kernel SETLFS calls to $ffba, the routine that sets the channel number, device and secondary address. This call occurs in exactly two places in Ultrafont+:
.C:ca32 A0 01 LDY #$01 .C:ca34 A9 01 LDA #$01 .C:ca36 20 BA FF JSR $FFBA .C:caf2 A9 00 LDA #$00 .C:caf4 20 BD FF JSR $FFBD .C:caf7 A9 0F LDA #$0F .C:caf9 A2 08 LDX #$08 .C:cafb A0 0F LDY #$0F .C:cafd 20 BA FF JSR $FFBA .C:cb00 20 C0 FF JSR $FFC0
The first call is curiously incomplete and doesn't seem to set a device number at all (it would be in the X register). The second one sets a null filename, then opens disk drive 8's command channel (the equivalent of OPEN 15,8,15 with no string). We definitely want to patch that too, but it's not what's being used to actually access any files.
Next I went looking for LOAD, reasoning that a binary font file would be LOADed using the Kernal file load call instead of byte-by-byte. That's at $ffd5, and this call appears exactly once:
.C:cb3c 20 0F CA JSR $CA0F .C:cb3f 20 52 CB JSR $CB52 .C:cb42 A9 00 LDA #$00 .C:cb44 20 D5 FF JSR $FFD5
LOAD still has to have the device number set somehow, so we look at the subroutines it calls first. It starts off with one at $ca0f.
.C:ca0f 20 E7 FF JSR $FFE7 .C:ca12 A9 36 LDA #$36 .C:ca14 A0 C4 LDY #$C4 .C:ca16 20 91 C4 JSR $C491 .C:ca19 20 E4 FF JSR $FFE4 .C:ca1c F0 FB BEQ $CA19 .C:ca1e A2 01 LDX #$01 .C:ca20 C9 54 CMP #$54 .C:ca22 F0 0B BEQ $CA2F .C:ca24 A2 08 LDX #$08 .C:ca26 C9 44 CMP #$44 .C:ca28 F0 05 BEQ $CA2F .C:ca2a 68 PLA .C:ca2b 68 PLA .C:ca2c 4C 8D C4 JMP $C48D .C:ca2f 8D 4D 02 STA $024D .C:ca32 A0 01 LDY #$01 .C:ca34 A9 01 LDA #$01 .C:ca36 20 BA FF JSR $FFBA
This routine closes all channels, then calls a utility routine to display a string at the bottom of the screen terminated by a Commodore backarrow character (ASCII 95). The string at $c436 is "{r}T{R}APE OR {r}D{R}ISK?" Hey, that looks familiar! It accepts a key and based on T or D sets the X register to 1 or 8 and falls through into $ca2f ... which completes our mysterious first SETLFS call.
What about for saves ($ffd8)?
.C:cab0 20 0F CA JSR $CA0F .C:cab3 20 52 CB JSR $CB52 .C:cab6 A9 00 LDA #$00 .C:cab8 85 FD STA $FD .C:caba 85 FB STA $FB .C:cabc A9 70 LDA #$70 .C:cabe 85 FC STA $FC .C:cac0 A2 FF LDX #$FF .C:cac2 A0 77 LDY #$77 .C:cac4 A9 FB LDA #$FB .C:cac6 20 D8 FF JSR $FFD8
It makes the same call to $ca0f and thus uses the same code to set the device. The last device number used by the system is stored in location 186, which is zero page, so we can replace a2 08 (LDX #8) with a6 ba (LDX 186) and not have to make any other adjustments. That means the following in-place changes to both the device prompt routine and the routine that opens the disk drive command channel (two bytes in each of two places; byte "address" is actually the offset within the main Ultrafont+ binary):
00000a00 99 00 02 20 d2 ff c8 4c ba c9 a9 5f 99 00 02 98 |... ...L..._....| 00000a10 60 20 e7 ff a9 36 a0 c4 20 91 c4 20 e4 ff f0 fb |` ...6.. .. ....| -00000a20 a2 01 c9 54 f0 0b a2 08 c9 44 f0 05 68 68 4c 8d |...T.....D..hhL.| +00000a20 a2 01 c9 54 f0 0b a6 ba c9 44 f0 05 68 68 4c 8d |...T.....D..hhL.| 00000a30 c4 8d 4d 02 a0 01 a9 01 20 ba ff a9 48 a0 c4 20 |..M..... ...H.. | 00000a40 c4 c4 20 b8 c9 d0 07 ad 4d 02 c9 54 d0 ed ad 4d |.. .....M..T...M| 00000ad0 d0 06 20 72 cb 4c 8d c4 20 72 cb 20 e7 ff ad 4d |.. r.L.. r. ...M| 00000ae0 02 c9 44 f0 0f a9 23 a0 c4 20 91 c4 20 e4 ff f0 |..D...#.. .. ...| -00000af0 fb 4c 8d c4 a9 00 20 bd ff a9 0f a2 08 a0 0f 20 |.L.... ........ | +00000af0 fb 4c 8d c4 a9 00 20 bd ff a9 0f a6 ba a0 0f 20 |.L.... ........ | 00000b00 ba ff 20 c0 ff a2 0f 20 c6 ff a0 00 20 cf ff c9 |.. .... .... ...| 00000b10 0d f0 07 99 00 02 c8 4c 0a cb a9 5f 99 00 02 20 |.......L..._... |
Save that, and we'll generate a nice compressed single-parter with the linker and pucrunch:
% linkb ufl.bas ufl9.bin Commodore 64 BASIC Linker for Perl (c)2006, 2022 Cameron Kaiser. Distributed under the Floodgap Free Software License; see documentation. Use /home/spectre/bin/linkb --version for version string and help information. Loaded 1068 bytes of BASIC text. BASIC text allocated from 2049 ($0801) to 3116 ($0c2c). Loaded ufl9.bin (3260 bytes) from 49152 ($c000) to 52411 ($ccbb). 4328 total bytes in raw binary data. Creating runnable relocator. Package successfully created. % pucrunch -fshort apkg.prg ultrafnt.prg Load address 0x0801=2049, Last byte 0x19a2=6562 Exec address 0x080d=2061 New load address 0x0801=2049 Interrupts enabled and memory config set to $37 after decompression Runnable on Commodore 64 Checked: 4514 Selecting the number of escape bits.. Selected 2-bit escapes Optimizing LZ77 and RLE lengths... Selecting LZPOS LO length.. Selected 8-bit LZPOS LO part Note: Using option -m6 you may get better results. In: 4514, out: 3516, ratio: 77.90% (6.24[5.76] b/B), gained: 22.11% Gained RLE: 119 (S+L:119+0), LZ: 1256, Esc: -90, Decompressor: -284 Times RLE: 35 (35+0), LZ: 690, Esc: 145 (normal: 1822), 2 escape bits Saving C64 short ultrafnt.prg uses the memory $2d-$30, $f7-$1d7, and $0801-$19aa. Compressed 4514 bytes in 0.00 seconds (2844.00 kB/sec)
For the record, -m6 saved me nothing and -m5 saved me a whole stinking byte. There wasn't much speed difference with -ffast either for this small of a program. Ah, it runs, who cares.
(C:$f13e) l "module03" 8 Loading module03 from 9000 to B55F (2560 bytes) (C:$f13e) l "module01" 8 Loading module01 from 5240 to 55BF (0380 bytes) (C:$f13e) l "module02" 8 Loading module02 from 8000 to 82BF (02C0 bytes)
At this point it doesn't load anything further (at least obligatorily) and the program is fully operational.
My first initial idea was to patch out the portions of the 75-block (!) booter that loaded these modules, link everything together, and use that as the one-part executable (the disk also contains printer drivers and sample images but we won't need those). With a little more work in VICE I was able to identify where the three modules loaded from (third module at $4ed5, then first module at $4ef7 and second at $4f14), but pre-loading the modules and turning those Kernal LOADs into no-ops caused the booter to abort with a "disk error" (despite the disk drive reporting 00, OK, 00, 00). Some additional disassembly, besides finding an odd routine at $2b47 that sends commands placed at $2b5c to the disk drive command channel and leaves it open, notes that it seems to frequently interrogate the disk drive for its status. This didn't look like copy protection or obfuscation and seemed more like paranoia on Mr. Rubin's part, but it was similarly unwelcome for this purpose.
I dithered over patching all of those calls out as well and seeing what was left, but it dawned on me I had already determined Doodle's entry point, so all I should need to do was drop a breakpoint when it got there and save memory from $0801 to $b55f (the very end of module03), then jump back in at $501a with the BASIC ROM banked out.
This almost worked. It turns out that Doodle also drops some data in low memory as well: when switching to the zoomed-in pixel editor, the sprite used for the cursor was garbled. Looking at the VIC-II registers I could see we were in the lowest 16K bank and the cursor's sprite pointer (as determined by location 53272, indicating the start of screen memory) was pointing to location 832 in the cassette buffer, which we didn't save. I noted what was there with Doodle loaded normally and searched for it in the dump, finding it at $5440. I also noticed that our background and foreground colours in the "colour mode" were a bit scrambled; disassembly around $47b1 shows Doodle keeps this value as two nybbles at $08 in zero page and this had been earlier initialized to 1 (black on white) prior to the main entry point. Since we're going to need a fixup trampoline to start Doodle from the memory dump anyway, I made a mental note to add that change as well. There are probably some other low memory variables that aren't getting initialized but I didn't notice any other problems either.
Now for the device number. Searching for SETLFS calls, I found multiple places where device 8 had been hardcoded (a2 08) and initially changed them to consult location 186 again (a6 ba), but Doodle went right on accessing device 8; location 186 somehow got reset somewhere, probably some non-obvious disk call I hadn't found yet. One solution might have been to watchpoint for where this happens and modify that, but doing so gets a lot of false hits in the Kernal and a simpler one is just to use another address in zero page Doodle isn't using and copy it there. 190 was free and didn't seem to get changed by anything, so patching the dump looked like this (remember that the "addresses" are file offsets):
00002320 01 d0 0b ad 78 08 c9 10 b0 03 ee 78 08 60 ce 77 |....x......x.`.w| 00002330 08 60 ad 78 08 c9 01 d0 0b ad 77 08 c9 10 b0 03 |.`.x......w.....| -00002340 ee 77 08 60 ce 78 08 60 48 a9 0f a2 08 a0 0f 20 |.w.`.x.`H...... | +00002340 ee 77 08 60 ce 78 08 60 48 a9 0f a6 be a0 0f 20 |.w.`.x.`H...... | 00002350 ba ff 68 a2 5c a0 2b 20 bd ff 4c c0 ff 49 10 05 |..h.\.+ ..L..I..| 00002360 29 7f 4c 6b 2b 48 a9 93 20 d2 ff 68 0a a8 b9 00 |).Lk+H.. ..h....| 00002490 08 a9 9b 20 5d 2b 4c 9d 2c a9 9c 20 5d 2b a9 99 |... ]+L.,.. ]+..| 000024a0 20 5d 2b a9 01 20 47 2b 20 cc 25 90 03 4c c4 30 | ]+.. G+ .%..L.0| -000024b0 a9 02 a2 08 a0 00 20 ba ff a9 01 a2 e8 a0 30 20 |...... .......0 | +000024b0 a9 02 a6 be a0 00 20 ba ff a9 01 a2 e8 a0 30 20 |...... .......0 | 000024c0 bd ff 20 c0 ff 20 34 26 90 03 4c c4 30 a2 02 20 |.. .. 4&..L.0.. | 000024d0 c6 ff a0 03 a2 0b 18 20 f0 ff a9 97 20 d2 ff 20 |....... .... .. | 00003b00 01 80 20 e4 ff d0 fb 4c d4 42 c9 56 d0 d4 4c eb |.. ....L.B.V..L.| 00003b10 43 a9 01 8d 52 08 20 77 2c ad a7 08 f0 b7 20 29 |C...R. w,..... )| -00003b20 44 20 10 0a a9 01 a2 08 a0 00 20 ba ff ad a7 08 |D ........ .....| +00003b20 44 20 10 0a a9 01 a6 be a0 00 20 ba ff ad a7 08 |D ........ .....| 00003b30 18 69 02 a2 aa a0 08 20 bd ff a9 00 a2 00 a0 5c |.i..... .......\| 00003b40 20 d5 ff a9 01 20 c3 ff 20 3f 44 a9 0f 20 c3 ff | .... .. ?D.. ..| 00003b50 20 a4 0a 4c d4 42 a9 00 8d 52 08 20 77 2c ad a7 | ..L.B...R. w,..| -00003b60 08 d0 03 4c d4 42 20 29 44 20 10 0a a9 01 a2 08 |...L.B )D ......| +00003b60 08 d0 03 4c d4 42 20 29 44 20 10 0a a9 01 a6 be |...L.B )D ......| 00003b70 a0 01 20 ba ff a9 40 8d a8 08 ad a7 08 18 69 04 |.. ...@.......i.| 00003b80 a2 a8 a0 08 20 bd ff a9 00 85 1b a9 5c 85 1c a9 |.... .......\...| 00003ba0 a9 0f 20 c3 ff 20 a4 0a 4c d4 42 a9 80 8d 52 08 |.. .. ..L.B...R.| 00003bb0 20 77 2c ad a7 08 d0 03 4c d4 42 20 29 44 a9 0f | w,.....L.B )D..| -00003bc0 20 c3 ff a9 0f a2 08 a0 0f 20 ba ff a9 53 8d a8 | ........ ...S..| +00003bc0 20 c3 ff a9 0f a6 be a0 0f 20 ba ff a9 53 8d a8 | ........ ...S..| 00003bd0 08 ad a7 08 18 69 04 a2 a8 a0 08 20 bd ff 20 c0 |.....i..... .. .| 00003be0 ff 20 3f 44 a9 0f 20 c3 ff 4c d4 42 a9 1f 20 5d |. ?D.. ..L.B.. ]| 00003bf0 2b 20 e4 ff f0 fb c9 59 f0 03 4c d4 42 20 29 44 |+ .....Y..L.B )D| -00003c00 a9 0f 20 c3 ff a9 0f a2 08 a0 0f 20 ba ff a9 56 |.. ........ ...V| +00003c00 a9 0f 20 c3 ff a9 0f a6 be a0 0f 20 ba ff a9 56 |.. ........ ...V| 00003c10 8d a8 08 a9 01 a2 45 a0 44 20 bd ff 20 c0 ff 20 |......E.D .. .. | 00003c20 3f 44 a9 0f 20 c3 ff 4c d4 42 a9 01 20 47 2b 20 |?D.. ..L.B.. G+ |
With that, we can now construct our trampoline. This assembles with xa and automatically links in the memory dump (stored as doodledump). I also added a "DECOMPRESSING DOODLE" message since we're in screen memory range anyway.
.word $0340
* = $0340
; sprite data for zoom mode
; copied from ($51 = 81 * 64 + 16384 = $5440)
.byt $00, $00, $00, $00, $00, $00, $0f, $ff, $f0, $0f, $ff, $f0, $0c, $00, $30, $0c
.byt $00, $30, $0c, $00, $30, $0c, $00, $30, $0c, $00, $30, $0c, $00, $30, $0c, $00
.byt $30, $0c, $00, $30, $0c, $00, $30, $0c, $00, $30, $0c, $00, $30, $0c, $00, $30
.byt $0f, $ff, $f0, $0f, $ff, $f0, $00, $00, $00, $00, $00, $00, $00, $00, $00, $00
; enter fixup code at $0380 = 896
; set up default screen
jsr $ff84 ; this resets $01
lda #$36
sta $01
lda #12
sta $d020
lda #1
sta $d021
; stash current device (186 gets overwritten)
lda 186
sta 190
; set ink to white background, black ink (see routine ~$47b1)
lda #$01
sta $08
; call the screen display routine $2b5d and enter main loop
jmp $501a
eot = *
; print helpful message
* = 1024+80+2
.dsb (*-eot),32
* = 1024+80+2
.asc "decompressing doodle ..."
eom = *
; account for starting address
* = $07ff
.dsb (*-eom),32
* = $07ff
.bin 0,0,"doodledump"
The screen portion requires the xa feature to transform ASCII into Commodore screen codes, so don't forget to add -O PETSCREEN to select the proper character set when assembling. We then pass a couple special options to pucrunch when generating the compressed single-parter.
% xa -O PETSCREEN -o dumple.o runner.xa % pucrunch +f -ffast -c64 -g54 -x896 dumple.o 1doodle Discarding execution address 0x080d=2061 Load address 0x0340=832, Last byte 0xb560=46432 Exec address 0x0380=896 New load address 0x0801=2049 Interrupts enabled and memory config set to $36 after decompression Runnable on Commodore 64 Checked: 45601 Selecting the number of escape bits.. Selected 2-bit escapes Optimizing LZ77 and RLE lengths... Selecting LZPOS LO length.. Selected 8-bit LZPOS LO part In: 45601, out: 18051, ratio: 39.59% (3.17[3.12] b/B), gained: 60.42% Gained RLE: 12424 (S+L:1119+11305), LZ: 15780, Esc: -320, Decompressor: -332 Times RLE: 187 (182+5), LZ: 4662, Esc: 512 (normal: 7920), 2 escape bits Saving C64 fast 1doodle uses the memory $2d/$2e, $f7-$1cd, $200-$234, and $0340-$b56a. Compressed 45601 bytes in 0.02 seconds (2113.24 kB/sec)
This makes the cruncher ignore the existing entry point and use our trampoline in low memory as the execution address, as well as setting banking correctly on exit. As part of the process, it will splash on our message as it decompresses it.
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