Add Socket::new_nonblocking

[taiki-e]

Equivalent to:

#[cfg(any(
    target_os = "android",
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "fuchsia",
    target_os = "illumos",
    target_os = "linux",
    target_os = "netbsd",
    target_os = "openbsd"
))]
let ty = ty.nonblocking();

let socket = Socket::new(domain, ty, protocol)?;

#[cfg(not(any(
    target_os = "android",
    target_os = "dragonfly",
    target_os = "freebsd",
    target_os = "fuchsia",
    target_os = "illumos",
    target_os = "linux",
    target_os = "netbsd",
    target_os = "openbsd"
)))]
socket.set_nonblocking(true)?;

I've seen code like this several times and thought it would be useful to have a constructor that does the same thing.

[chansuke]

I appreciate your work. Seems good for me.

[Thomasdezeeuw]

I'm not sure about this. I understand you wanting to reduce the code duplication, but where do we draw the line when it comes to constructors? We already have two variants: "new" and "raw", do we also want raw_nonblocking? What about pair_nonblocking? etc.

[Darksonn]

Maybe there's a more general way to do this where we define a flags type which has a nonblocking flag, then use that?

[Thomasdezeeuw]

Maybe there's a more general way to do this where we define a flags type which has a nonblocking flag, then use that?

We could add our own bit to Type on the OSs that don't support Type::non_blocking (making it available on all OSs) and make the Socket::set_nonblocking call inside Socket::new. Only difficulty here is ensuring the bit is never used by an OS flag (like SOCK_NONBLOCK).

[hawkw]

I'm not sure about this. I understand you wanting to reduce the code duplication, but where do we draw the line when it comes to constructors? We already have two variants: "new" and "raw", do we also want raw_nonblocking? What about pair_nonblocking? etc.

This seems like a potential argument for a SocketBuilder or something?

let sock = SocketBuilder::new()
    .nonblocking(true)
    .finish(domain, ty, protocol);

let raw = SocketBuilder::new()
    .nonblocking(true)
    .finish_raw(domain, ty, protocol);

or similar?

[Thomasdezeeuw]

This seems like a potential argument for a SocketBuilder or something?

let sock = SocketBuilder::new()
    .nonblocking(true)
    .finish(domain, ty, protocol);

let raw = SocketBuilder::new()
    .nonblocking(true)
    .finish_raw(domain, ty, protocol);

or similar?

We already have that in the Domain, Type Protocol types. It just that currently socket2 is mostly just wraps around system calls where 1 function = 1 system call, thus if the OS doesn't support a flag, like SOCK_NONBLOCK here, socket2 currently leaves it up to the user to handle properly. We could break from 1 function = 1 system call though and implement these kind of niceties in Socket::new.

[taiki-e]

Closing in favor of the idea proposed in #293 (comment).