Release Java FFST as separate library on Maven Central

[louwers]

This is a pain...

maplibre-tile-spec/java/mlt-core/src/main/java/org/maplibre/mlt/converter/encodings/fsst/FsstJni.java

Line 5 in 8c14c38

class FsstJni implements Fsst {

maplibre-tile-spec/java/resources/CMakeLists.txt

Line 42 in 8c14c38

ExternalProject_Add(FsstDownload

cc @TimSylvester

[mactrem]

@msbarry has implemented a pure Java FSST Encoder that performed well in my tests. Do we still need to maintain the JNI implementation?

[louwers]

Good question. @TimSylvester can probably better answer that. He mentioned there's some other differences between the two besides performance.

I have put up a Java package now. https://central.sonatype.com/artifact/nl.bartlouwers/fsst4j. It uses the new Foreign Function & Memory API instead of JNI. If it turns out that it works well cross-platform, I guess it doesn't really matter that it's not pure Java.

[msbarry]

The java FSST port should produce valid, but not byte-for-byte identical output to the native FSST library. In my testing the output was more compact than native FSST library. The main drawback is that encoding is quite a bit slower than native. I squeezed as much performance as I could get out of it while maintaining readability but to go further we'd probably want to use jni instead.

Decoding FSST is simple, we shouldn't need to use a native library for that.