#1209 requesting lz4 compression method id

[Chris Hecker]

Hi, the Methods.txt says to contact you to allocate compression method ids. I want to add lz4 support to 7-zip, and don't want to stomp any other IDs. I'll contribute the code back, of course. Would this work?

const UInt32 k_LZ4 = 0x040A01;

Basically, allocating 10 beyond NSIS's 09, and then 01 under that?

Thanks,
Chris

[Igor Pavlov]

There is also another id list in GUID.txt.

What exact thing do you want to implement?
It can be

• LZ4 block in 7z format
• LZ4 frame in 7z format
• LZ4 frame as archive file for 7-Zip (as format handler)
• or something else?

[Chris Hecker]

Ah, found guid.txt, it wasn't in the root directory of the lzma sdk, so I missed it on my first pass.

What exact thing do you want to implement?

I'm not sure which of the ones you listed is the name for what I want since I'm just starting to dig into this, but I'd like for files in the 7z archive to be compressed with lz4, so I can keep using the 7z format, but take advantage of lz4's decompression speed when I don't need the compression ratio and can make the speed/size tradeoff. Basically, if I was going to hack it in, I think I'd make another case in in SzFolder_Decode2 in 7zDec.c file I'd like to be able to have a k_LZ4 in the list of method ids.

Hopefully that makes sense?

Chris

[Igor Pavlov]

For test purposes you can generate 8-bytes ID as described in Methods.txt.
If you will have working code, I can assign short ID for that method.