Re: [B2-devel] Compressed NewWorld ROMs

[Gwenole B. <gb...@di...>]

Hi,

> The decoding routine should be somewhere in the ELF part. Maybe you can 
> get
> the parameters from there.

OK, the ROM Trampoline code is generally located at rom_tmp + 
elf_offset + 0x100; I then dumped trampoline code of both v1.6 and v3.8 
NewWorld ROMs. Searching for $0fee (dict_idx) is sucessful in both cases 
and the decompression routines are exactly the same. Besides, what you 
implemented in decode_lzss() turns out to exactly match that code in 
higher level language. ;-)

I came up to the same solution with crf0 - crf2 propagation and partial 
redundancy elimination for run_mask computations. So, I am pretty sure 
the implementation is correct.

There are some differences in the code preceding the call to the 
decompression routine betwen the above-mentioned ROMs. I have not looked 
at them in further details yet but I suspect some pattern is first 
applied to the uncompressed ROM area prior to decompressing it in the 
v3.8 ROM case? This would be weird or they probably compressed several 
hunks/resources independently ? That might explain why in newer ROMs 
(v3.x), strings|grep -i lzss yield more results than with v1.x ROMs.

Bye,
Gwenole