You can grab the version from the solaris userland repo I linked and use it without me completing a homework assignment. Just grab the pigz-2.3.4 source then apply the patches from [1] in the proper order. Maybe some of them aren't needed for non-Solaris.
I thought I had opened a PR for that a long while ago, but it doesn't show up on github these days. In any case, I did ask Mark Adler to review it. It was never a priority, then the code changed in ways that I don't really want to deal with.
While looking through the PRs, I noticed a PR for Blocked GZip Format (BGZF) [2]. That's very interesting, and perhaps suggests that bgzip is a tool you would be interested in.
