LZH decompression of disk images?

[jpoikela]

some archives have files available as LZH compressed disk images, e.g beamride.lzh. on-demand decompression of these disc images would make use of these files a lot more user friendly.

would it be feasible to try to uncompress given LZH image and proceed similar to what is done with ZIP disk images?
I have not tested compatibility with MSX files, but at least npm has lzh package available. I have used lhasa to decompress the files and then load the directory as disk to run that kind of images, which is doable, but cumbersome.

[jpoikela]

tried to use npm package "lzh" but it does not compile 😒

[ppeccin]

Hi! Yes, I plan to add it, but I have not yet found a good way to do it in javascript. What you mean it does not compile? Can you direct me to this project? Are you sure it is a complete implementation of the decompression algorithm? Paulo

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On Wed, Jul 11, 2018 at 8:57 AM Jani Poikela ***@***.***> wrote: tried to use npm package "lzh" but it does not compile 😒 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#36 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AArloCHWFODzH0aAGp_VXVE4wTjx32baks5uFegsgaJpZM4VFgol> .

[jpoikela]

I tried to make a simple node command line with lzh package ( https://www.npmjs.com/package/lzh), to try if it can decompress MSX lzh files.. it has a C-implementation, that does not compile.. didn't have time to look deeper, though. rewriting lzh in JS could make sense if it was a good implementation (it's very small), but so far I don't know if it is a good one. lhasa is more complete implementation, maybe it should be used for JS rewrite, then.. ke 11. heinäk. 2018 klo 18.29 ppeccin <notifications@github.com> kirjoitti:

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Hi! Yes, I plan to add it, but I have not yet found a good way to do it in javascript. What you mean it does not compile? Can you direct me to this project? Are you sure it is a complete implementation of the decompression algorithm? Paulo On Wed, Jul 11, 2018 at 8:57 AM Jani Poikela ***@***.***> wrote: > tried to use npm package "lzh" but it does not compile 😒 > > — > You are receiving this because you are subscribed to this thread. > Reply to this email directly, view it on GitHub > <#36 (comment)>, or mute > the thread > < https://github.com/notifications/unsubscribe-auth/AArloCHWFODzH0aAGp_VXVE4wTjx32baks5uFegsgaJpZM4VFgol > > . > — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#36 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAF5crGcC47vVHZdnM2VpwBtBTUaJuYGks5uFhnKgaJpZM4VFgol> .

[jpoikela]

well, the lhasa implementation is not too complex either.. starting at: https://github.com/fragglet/lhasa/blob/master/src/extract.c#L575

[jpoikela]

in a search for an easy solution I made a Kaitai struct
https://gist.github.com/jpoikela/f4be749de62bb9716856835829f9a03f
that can be tried with https://ide.kaitai.io/# and some lzh file.. seems to get the file parts correctly for my one sample file beamride.lzh, but I only added logic for level 0 and level 1 headers.. level 2 header seemed to be a bit more complex with that tool... and still would need code to decompress the byte arrays...

[jpoikela]

btw, I followed this information about the level 0 and level 1 headers:
https://ist.uwaterloo.ca/~schepers/formats/LHA.TXT

[jpoikela]

I try to make a POC with Kaitai, it can be dropped if we get to write stand-alone file parsing..

[jpoikela]

also, running lhasa through emscripten could be worth a POC..

[jpoikela]

well, both seems too cumbersome.. I'll be writing a lhasa-inspired LHZ decoder in JS.

[ppeccin]

Nice! If you can keep it as simple and as light as possible, we can integrate it into WebMSX. If you allow, of course! Paulo

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On Tue, Jul 17, 2018 at 1:13 PM Jani Poikela ***@***.***> wrote: well, both seems too cumbersome.. I'll be writing a lhasa-inspired LHZ decoder in JS. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#36 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AArloPnjoDP8nFWwh0n6cKb1HTdauQjQks5uHg0rgaJpZM4VFgol> .

[jpoikela]

it's definitely my goal to make it usable for your great WebMSX 🙂

I already wrote some parts, but it may take a week or two to have anything usable - I have not written that much JS.. I might need some help, too.
I write it as old-style prototype classes for now. I might modernize it later.

[ppeccin]

Remember, WebMSX is not ES6 yet. So, if possible, try to keep it ES5, or maybe we won't be able to use it. Also, you should have a look at the ZIP implementation of WebMSX, and how it is used, so you can make your interface as close as possible. You know, the way we must pass the compressed bytes, the way we take the uncompressed files out, etc. Have fun!

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On Thu, Jul 19, 2018 at 6:36 AM Jani Poikela ***@***.***> wrote: it's definitely my goal to make it usable for your great WebMSX 🙂 I already wrote some parts, but it may take a week or two to have anything usable - I have not written that much JS.. I might need some help, too. I write it as old-style prototype classes for now. I might modernize it later. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#36 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AArloBxheKJnh9X5lWkAj9-rlCgB7-Gfks5uIFMjgaJpZM4VFgol> .

[jpoikela]

hi!
I just got first decompression hacked and run in webMSX 😅
the biggest struggle was with the bit buffer.
now, I only have lh0 and lh5 decoders, but I have the impression that I will get some decoders with quite little additional work. the code is a little bit of a hack still, especially the Zip API and integration..

I am a little bit uncomfortable with publishing my code just yet.. I try to make it cleaner first, publish it and the add more decoders.

[jpoikela]

I made a PR, but it's still a work in progress.. still only the lh0 and lh5 decoders.. and not clean code, but a something to try out, if interested..
#37

[ppeccin]

Ok! Thank you very much!!! I need to look at this carefully before moving on. I will let you know... Meanwhile, feel free to make improvements and newer versions while I find the time to look at the code. Paulo

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On Mon, Aug 6, 2018 at 11:16 AM Jani Poikela ***@***.***> wrote: I made a PR, but it's still a work in progress.. still only the lh0 and lh5 decoders.. and not clean code, but a something to try out, if interested.. #37 <#37> — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#36 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AArloBAVtgTRUxBCPGulzUlpeKf9fOsqks5uOE-8gaJpZM4VFgol> .