About the compression mechanism

[chainsawriot]

As there are many bugs (#395 #396 #399) after really testing this bunch of code (#354)

Other than the issues of compression detection, this

https://github.com/gesistsa/rio/blob/2fb1373a497f586dacce095300452ccc5a42cf37/R/compression.R#L25-L44

is super not robust (e.g. it won't return a file and o is still 0). Instead of using this, the plan is to use the battle-tested R.utils compression. Well, even data.table is using it and that's the reason for introducing R.utils in the first place #362 .

https://github.com/Rdatatable/data.table/blob/2487c61656335764980e478c323f7e6ce4e6d4ca/R/fread.R#L123

But the problem is that R.utils doesn't support xz. (But I think it should be okay to cut xz. No one complains about xz not functioning, although it is not functioning for so many years.)