getAddressList

pub fn getAddressList(gpa: Allocator, name: []const u8, port: u16) GetAddressListError!*AddressList {
    const result = blk: {
        var arena = std.heap.ArenaAllocator.init(gpa);
        errdefer arena.deinit();

        const result = try arena.allocator().create(AddressList);
        result.* = AddressList{
            .arena = arena,
            .addrs = undefined,
            .canon_name = null,
        };
        break :blk result;
    };
    const arena = result.arena.allocator();
    errdefer result.deinit();

    if (native_os == .windows) {
        const name_c = try gpa.dupeZ(u8, name);
        defer gpa.free(name_c);

        const port_c = try std.fmt.allocPrintSentinel(gpa, "{d}", .{port}, 0);
        defer gpa.free(port_c);

        const ws2_32 = windows.ws2_32;
        const hints: posix.addrinfo = .{
            .flags = .{ .NUMERICSERV = true },
            .family = posix.AF.UNSPEC,
            .socktype = posix.SOCK.STREAM,
            .protocol = posix.IPPROTO.TCP,
            .canonname = null,
            .addr = null,
            .addrlen = 0,
            .next = null,
        };
        var res: ?*posix.addrinfo = null;
        var first = true;
        while (true) {
            const rc = ws2_32.getaddrinfo(name_c.ptr, port_c.ptr, &hints, &res);
            switch (@as(windows.ws2_32.WinsockError, @enumFromInt(@as(u16, @intCast(rc))))) {
                @as(windows.ws2_32.WinsockError, @enumFromInt(0)) => break,
                .WSATRY_AGAIN => return error.TemporaryNameServerFailure,
                .WSANO_RECOVERY => return error.NameServerFailure,
                .WSAEAFNOSUPPORT => return error.AddressFamilyNotSupported,
                .WSA_NOT_ENOUGH_MEMORY => return error.OutOfMemory,
                .WSAHOST_NOT_FOUND => return error.UnknownHostName,
                .WSATYPE_NOT_FOUND => return error.ServiceUnavailable,
                .WSAEINVAL => unreachable,
                .WSAESOCKTNOSUPPORT => unreachable,
                .WSANOTINITIALISED => {
                    if (!first) return error.Unexpected;
                    first = false;
                    try windows.callWSAStartup();
                    continue;
                },
                else => |err| return windows.unexpectedWSAError(err),
            }
        }
        defer ws2_32.freeaddrinfo(res);

        const addr_count = blk: {
            var count: usize = 0;
            var it = res;
            while (it) |info| : (it = info.next) {
                if (info.addr != null) {
                    count += 1;
                }
            }
            break :blk count;
        };
        result.addrs = try arena.alloc(Address, addr_count);

        var it = res;
        var i: usize = 0;
        while (it) |info| : (it = info.next) {
            const addr = info.addr orelse continue;
            result.addrs[i] = Address.initPosix(@alignCast(addr));

            if (info.canonname) |n| {
                if (result.canon_name == null) {
                    result.canon_name = try arena.dupe(u8, mem.sliceTo(n, 0));
                }
            }
            i += 1;
        }

        return result;
    }

    if (builtin.link_libc) {
        const name_c = try gpa.dupeZ(u8, name);
        defer gpa.free(name_c);

        const port_c = try std.fmt.allocPrintSentinel(gpa, "{d}", .{port}, 0);
        defer gpa.free(port_c);

        const hints: posix.addrinfo = .{
            .flags = .{ .NUMERICSERV = true },
            .family = posix.AF.UNSPEC,
            .socktype = posix.SOCK.STREAM,
            .protocol = posix.IPPROTO.TCP,
            .canonname = null,
            .addr = null,
            .addrlen = 0,
            .next = null,
        };
        var res: ?*posix.addrinfo = null;
        switch (posix.system.getaddrinfo(name_c.ptr, port_c.ptr, &hints, &res)) {
            @as(posix.system.EAI, @enumFromInt(0)) => {},
            .ADDRFAMILY => return error.HostLacksNetworkAddresses,
            .AGAIN => return error.TemporaryNameServerFailure,
            .BADFLAGS => unreachable, // Invalid hints
            .FAIL => return error.NameServerFailure,
            .FAMILY => return error.AddressFamilyNotSupported,
            .MEMORY => return error.OutOfMemory,
            .NODATA => return error.HostLacksNetworkAddresses,
            .NONAME => return error.UnknownHostName,
            .SERVICE => return error.ServiceUnavailable,
            .SOCKTYPE => unreachable, // Invalid socket type requested in hints
            .SYSTEM => switch (posix.errno(-1)) {
                else => |e| return posix.unexpectedErrno(e),
            },
            else => unreachable,
        }
        defer if (res) |some| posix.system.freeaddrinfo(some);

        const addr_count = blk: {
            var count: usize = 0;
            var it = res;
            while (it) |info| : (it = info.next) {
                if (info.addr != null) {
                    count += 1;
                }
            }
            break :blk count;
        };
        result.addrs = try arena.alloc(Address, addr_count);

        var it = res;
        var i: usize = 0;
        while (it) |info| : (it = info.next) {
            const addr = info.addr orelse continue;
            result.addrs[i] = Address.initPosix(@alignCast(addr));

            if (info.canonname) |n| {
                if (result.canon_name == null) {
                    result.canon_name = try arena.dupe(u8, mem.sliceTo(n, 0));
                }
            }
            i += 1;
        }

        return result;
    }

    if (native_os == .linux) {
        const family = posix.AF.UNSPEC;
        var lookup_addrs: ArrayList(LookupAddr) = .empty;
        defer lookup_addrs.deinit(gpa);

        var canon: ArrayList(u8) = .empty;
        defer canon.deinit(gpa);

        try linuxLookupName(gpa, &lookup_addrs, &canon, name, family, .{ .NUMERICSERV = true }, port);

        result.addrs = try arena.alloc(Address, lookup_addrs.items.len);
        if (canon.items.len != 0) {
            result.canon_name = try arena.dupe(u8, canon.items);
        }

        for (lookup_addrs.items, 0..) |lookup_addr, i| {
            result.addrs[i] = lookup_addr.addr;
            assert(result.addrs[i].getPort() == port);
        }

        return result;
    }
    @compileError("std.net.getAddressList unimplemented for this OS");
}