Lib.rs

As the README claims, this locks files using the fcntl libc method, and it provides locks for both read and write access. I've read the man pages for that thoroughly and compared it to the implementation of this crate, and at least the C part of it is nearly perfect. I would have named some things differently, but aside of that, this part is good as it stands. It always locks the whole file, uses the proper flags and in general looks good. As for the rust part.. well, that's where the problems begin. The Drop impl does unlock the file, but ignores the result of the unlocking (it calls .is_ok() on the Result and ignores the return value, which is an antipattern also present in all of the test cases). When aquiring an exclusive lock, it disables read access to the file, causing bad fd errors when trying to read anyway. Last but not least, this crate hasn't been updated for the 2018 edition, has tons of warning and is using the deprecated and unmaintained gcc crate. These problems are easily fixable, and where I'm using the crate, I'm using my fork which has all these problems fixed, but considering that the other 3 MRs of the last year haven't been fixed either, I have my doubts about this still being maintained. If upstream continues to not respond, I'll fork this and update my review with an alternative accordingly.