std.posix: adding getsockopt

[mrjbq7]

I noticed that std.posix.setsockopt exists but not std.posix.getsockopt.

I tried to add it, but I'm not sure if the anyopaque / optlen approach is a good one.

https://linux.die.net/man/3/getsockopt

[mrjbq7]

Hi @alexrp I made the changes you suggested above.

[mrjbq7]

Okay, so I made a patch moving from opaque pointers:

pub fn getsockopt(fd: socket_t, level: i32, optname: u32, noalias optval: ?*anyopaque, noalias optlen: *socklen_t) GetSockOptError!void {

to slices:

pub fn getsockopt(fd: socket_t, level: i32, optname: u32, opt: []u8) GetSockOptError!void {

And to use it, you do this

var bytes = std.mem.toBytes(@as(c_int, 0));
try std.posix.getsockopt(socket, std.posix.SOL.SOCKET, std.posix.SO.SNDBUF, &bytes);
std.debug.print("send buffer size: {}\n", .{std.mem.bytesToValue(c_int, &bytes)});

I dunno if I like it, although it is a safer interface maybe.

It almost feels like it would be nicer to do something like passing the type in, but probably doesn't work for all sockopts

const size = try std.posix.getsockopt(socket, std.posix.SOL.SOCKET, std.posix.SO.SNDBUF, c_int);

[alexrp]

There's definitely room for discussion around []u8 vs *anyopaque vs generics, but I think that should be a separate issue. For this initial implementation, it's best to just follow the existing precedent, I think.

[alexrp]

CI is failing due to formatting issues.

[mrjbq7]

@alexrp ok i pushed a zig fmt patch, CI is restarting, thank you.