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Forums > C64 Coding > Pack chunks and depack anywhere EXOMIZER

2018-02-18 21:16

Golara
Account closed

Registered: Jan 2018
Posts: 212

Pack chunks and depack anywhere EXOMIZER

I have a question about the exomizer. In my demo part there's a lot of empty bytes between specific parts. For example, my code starts at $0801 and ends at about 2500, my music is at 2700, then i put stuff in the vic bank $4000, inside the bank i skip forward to $5000 to load bitmap etc...

Of course exomizer is quite good at packing this anyway, since it's just zeros, but I'm sure it can be better. I could put all my data back to back, compress that, extract and then copy it where I want it, but I'm sure there's an option to pack the stuff separatelly and just extract it to a specific address. The question is, how do you do it ? I can't find any exomizer tutorials or documentation except on how to do a basic sfx program.

This is what I'm looking for more or less

*=0801
; the addres of packed stuff
; and destination on some ZP addr
lda #<packed_for_0x1000
sta $10
lda #>packed_for_0x1000
sta $11
lda #$00
sta $12
lda #$10
sta $13
jsr depacker
; depack next stuff
lda #<packed_for_0x4000
sta $10
lda #>packed_for_0x4000
sta $11
lda #$00
sta $12
lda #$40
sta $13
jsr depacker
; depack next stuff
lda #<packed_for_0x6000
sta $10
lda #>packed_for_0x6000
sta $11
lda #$00
sta $12
lda #$60
sta $13
jsr depacker
depacker:
!binary depacker.bin
;-------
packed_for_0x1000:
!binary some_stuff_for_0x1000.bin
packed_for_0x4000:
!binary some_stuff_for_0x4000.bin
packed_for_0x6000:
!binary some_stuff_for_0x6000.bin
....

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2018-02-22 11:32

Krill

Registered: Apr 2002
Posts: 2850

Quoting Zirias

Krill, this was about zero-filling as a side effect of decrunching vs. calling the decruncher multiple times for individual chunks (and **not** zero-filling at all between them).

Alright, sorry then. But yes, calling a decruncher multiple times for several chunks adds not only table-building overhead, but also decreases overall pack ratio. The zero-filled areas themselves might not be filled that much slower than with a dedicated zero-fill routine, and in the multiple decrunch scenario, the decruncher would have to fetch more literals than copy sequences, with the former seeming a tad slower than the latter.

2018-02-22 12:08

Zirias

Registered: Jan 2014
Posts: 48

Indeed, that's why I suggested to measure the individual case in order to be sure ;) That is, *if* you want to optimize the total decrunching time.

Another option might be to use a stream decruncher and implement the logic for skipping areas yourself, but that's probably just over the top.

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