2.5 KiB
shrinking with shinkler
In this example I try to integrate the amazing and generally super awsome Shrinkler exe shrinker.
- Source repository
- [Forum thread with discussion] (http://ada.untergrund.net/?p=boardthread&id=264&page=0)
This is a pretty cool bit of kit. I think you can just point an exe and this program and it will produce a compressed version of the exe that it runnable. Seeing as all my examples are based on a trackloaded setup, we use it slightly differently.
We shrink the "program" that our trackloaded loads as if it were data:
Shrinkler -d out/main.bin out/shrunk.bin
Shrinker does a very impressive job of shrinking data:
```
Crunching...
Original After 1st pass After 2nd pass 51752 27545.297 26682.832
For comparison:
```
# gzip out/main.bin
# ls -l out/main.bin.gz
-rwxr-xr-x 1 alpine staff 29811 Mar 16 06:04 main.bin.gz
So now we have compressed data we need the bootloader to decompress it after it has loaded it. See ../shared/shrinkler_bootblock.s for the modified bootblock. But in a nutshell it's as simple as:
```
; a0 = compressed data lea DECOMPRESS_ADDRESS,a0 ; Where we asked the trackloaded to load the compressed data ; a1 = decompressed data destination lea BASE_ADDRESS,a1 ; The location of the decompressed code. ; a2 = progress callback, can be zero if no callback is desired. lea Callback(pc),a2 bsr ShrinklerDecompress ; -> decompress!
With our progress callback as simple as:
```
Callback:
;; d0 = Number of bytes decompressed so far
;; a0 = Callback argument
move.l a6,-(sp)
lea CUSTOM,a6
move.w d0,COLOR00(a6) ; Set wild background colors as we decompress
move.l (sp)+,a6
rts
And then we just include the Shrinkler decompression code:
```
include "../tools/external/shrinkler/ShrinklerDecompress.S"
In the [Makefile](Makefile) we can enable or disable Shrinkler:
```
SHRINKLER=1
In this example I have also started to refactor the structure of the code base ready for slightly more complex examples going forward.