I played a bit with deflateOutStream but it go to nowhere. I want to set level to 9 for example zip file myzip.zip, that all file added to this zip will be compressed with level 9. Please help.

I'm a bit confused by your question, as Zip.deflateOutStream() just compresses a stream of data - nothing to do with entries in a Zip file.

To compress a single file using deflate compression, try this:

out   := `output.df`.toFile.out
dfOut := Zip.deflateOutStream(out, ["level":9])

`myFile.txt`.toFile.in.pipe(dfOut)

dfOut.close

So how to set zip.write(...) compression level to 9? By default it compression level is very low. I read the api doc many time but found nothing regarding it, only about deflate out stream :(

Just curious. How to decompress deflate out stream above? What is the usage of it if not with zip file?

There is no means to set the compression level when managing .zip files - I've not noticed the default level being particularly low.

Compressing / decompressing streams is useful when performing compression yourself, for example, when sending or receiving data over HTTP.

To deflate files, use the Zip.deflateInStream() method, something like:

in   := `input.df`.toFile.in
dfIn := Zip.deflateInStream(in)
data := dfIn.readAllBuf


`myFile.txt`.toFile.out.writeBuf(data).close