Devine Lu LinvegaNov 16, 2023

So, for a little project I needed to compress a bit of data, and @cancel and I made up a spec that should be possible to implemented on small systems without too much headaches.

I wrote a bit of documentation for it, and I was wondering if anyone wanted to put the docs to the test and see if they could write a toy implementation in a language of their choice. It'd help me see if there's things missing in the docs.

http://wiki.xxiivv.com/site/ulz_format

So, think of it as a little puzzle.

XXIIVV — ulz format

Show threadRenaud BédardNov 16, 2023
@neauoire @cancel trying my hand at a C# version of this!
Show threadDevine Lu LinvegaNov 16, 2023
@renaudbedard @cancel Keep me posted :>
Show threadRenaud BédardNov 16, 2023
@neauoire @cancel A couple of things that are tripping me :
- CPY uses a "negative offset plus 1", but it's not clear if it's "-offset + 1" or "-(offset + 1)"
- It's implied that the dictionary pointer is always pointing to the end of the dictionary buffer after the last copy/append operation, right?
Show threadDevine Lu LinvegaNov 16, 2023

@renaudbedard @cancel

Example: an offset of 0 means go back by 1 bytes into the history.

And the pointer is the at the end of the dictionary buffer yep.

I'll add a bit about the negative increment to the offset to the docs! thanks for pointing it out

Show threadRenaud BédardNov 16, 2023
@neauoire @cancel also I know HTML tables are a nightmare, but if you could make the LIT length box appear to take all 7 bits instead of 6 like CPY1... 
Show threadRenaud BédardNov 16, 2023
@neauoire @cancel wait a minute... if the length of a CPY is greater than its negative offset, what's the expected behavior?
Show threadcancelNov 16, 2023
@renaudbedard @neauoire 
Show threadRenaud BédardNov 16, 2023
@cancel @neauoire that part was definitely unclear to me, but if I loop over the offset until length is hit, it does decode the test case! 🎉
Show threadcancel
@renaudbedard @neauoire nice :D here's my original version of the document from like 9 months ago https://gist.github.com/randrew/b43c011ccb44cb8cc6fa9d009ac58a7f the one you read was written by devine after reading mine, so the game of telephone appears to work
uxn lz explanation.md

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Nov 16, 2023 at 2:45amWeb