request: extension to NuFX file format

[peterferrie]

We would like to extend the data_thread type to include thread_format #6, to define compression using ZX0 format (https://github.com/einar-saukas/ZX0). That's the only change, the thread format is the same. We have examples if you want them for CiderPress support.

[fadden]

As noted in the NuFX Addendum and the NufxLib.h header, format 6 is Deflate, 7 is bzip. These were optionally supported by NuLib2 and the original CiderPress, though I don't think anybody used them, and it looks like I disabled Deflate in CiderPress at some point.

I'm totally fine with making ZX0 format 8. The ZX0 README notes a file format change in version 2; is that the version you would want to use?

Examples would be lovely.

[peterferrie]

Okay, I was looking at the https://nulib.com/library/FTN.e08002.htm. Here's one sample file (the "AE" entry at the end, but checksum is not correct yet), and some reference code that knows how to read it, using format 8. Yes, version 2 of ZX0. Thank you.

[fadden]

Doesn't look like the files got attached?

[peterferrie]

COMPANION#E08002.zip

shk.zip

[fadden]

I've added ZX0 support to CiderPress II v1.0.8-dev1 as an experimental feature. See fadden/CiderPress2#49 for information about how to use it. Basically you pass a magic option to the command-line tool to override the default compression algorithm.

CP2 gets upset by bad data checksums, but when the tests are disabled your sample file unpacks correctly.

Here's a sample: test.zip

One thing to note: the ZX0 format is incapable of representing a zero-length file. I handled this by generating zero bytes of output, and having the decompressor recognize the situation.

[peterferrie]

Super! Thank you! We will produce proper checksums for future files. I just hacked the example that I shared.

[fadden]

I've updated the thread format definitions in the NuFX Addendum and the NufxLib.h header file, and added code to display "ZX0" in file listings. I'm not planning to take it any further at this time, but that should be enough to avoid collisions and confusion.

[peterferrie]

Thank you, that sounds like all that we need, and this request can be closed now.