Add BlockSize and BlocksCount fields for FileStatus

[guibou]

(This is a request for discussion, there is, at least, one point which must be handled before merging this code)

The system stat function returns blocksize and blocks count for the file, which are not handled by current implementation. I added the accessor for both fields.

Discussion

I think the new types aliases:

type BlockSize = CSsize
type BlocksCount = CSsize

Should be placed somewhere else (in base ?) and I'm not really sure that's the correct types.

[argiopetech]

Thanks for your work on this, guibou.

Regarding the aliases, those would go in System.Posix.Types. That will require a pull request against base. I'm honestly not sure what the historical context is for those definitions to be in base rather than unix, but I imagine there's a good reason for it. We'll need to bump the lower bound on the base version dependency in unix.cabal to match the upcoming base release in order to ensure those types are available.

[argiopetech]

Oh, and you are correct about the types needing to be changed. CSsize is equivalent to size_t, but the current POSIX spec specifies blkcount_t and blksize_t for st_blksize and st_blocks (respectively). Those will need to be added as new types using the INTEGRAL_TYPE or INTEGRAL_TYPE_WITH_CTYPE macros.

[DanielG]

I just created a trac ticked for this and patches to both base and unix are forthcoming: https://ghc.haskell.org/trac/ghc/ticket/12795

[guibou]

@argiopetech Thanks to @DanielG changes to base, I can now update this PR without the ugly type aliases.

(Yes, two years had passed ;)

[DanielG]

Probably should have mentioned this before but I also have a PR open for this: #78. It handles platforms where st_blksize doesn't exist which this PR doesn't.

[guibou]

@DanielG good point. I'm closing in favor of #78