Support POSIX MAP_FIXED

[ShaneEverittM]

Would it be possible to support this flag? Currently the much older crate mmap supports it, but it hasn't been updated in 6 years (!).

[RazrFalcon]

Why do you need it?

Anyway, patches are welcome.

[ShaneEverittM]

It's kind of an niche use case, I'm playing around with writing a ELF loader. I could submit a patch, but it would be just for me. Though as I work on it more I probably won't need to use MAP_FIXED it's kind of a hack.

[adamreichold]

I think the main point of this crate is providing a portable abstraction of the memory mapping facilities available on Unix- and Windows-like operating systems. I suspect that your ELF loader does not have those portability requirements? Maybe using a Unix-specific lower level crate like nix or libc would be a better choice due to this?

[norcalli]

There's already flagged things like mremap which are under #[cfg(linux)], so adding MAP_FIXED under a flag seems like not that big of a stretch.

[RazrFalcon]

@norcalli The are OS-specific stuff now, but not 2 years ago.

Either way, patches are welcome.