LookupDnsWindows

const LookupDnsWindows = struct {
    threaded: *Threaded,
    thread: Thread.Handle,
    resolved: *Io.Queue(HostName.LookupResult),
    options: HostName.LookupOptions,
    results: windows.DNS.QUERY.RESULT,
    done: bool,

    fn completed(
        pQueryContext: ?*anyopaque,
        pQueryResults: *windows.DNS.QUERY.RESULT,
    ) callconv(.winapi) void {
        _ = pQueryContext;
        const lookup_dns: *LookupDnsWindows = @fieldParentPtr("results", pQueryResults);
        lookup_dns.completedFallible() catch |err| switch (err) {
            error.Closed => unreachable, // `resolved` must not be closed until `netLookup` returns
            error.Canceled => unreachable, // called from an uncancelable thread
        };
        @atomicStore(bool, &lookup_dns.done, true, .release);
        _ = windows.ntdll.NtAlertThread(lookup_dns.thread);
    }
    fn completedFallible(lookup_dns: *LookupDnsWindows) (Io.QueueClosedError || Io.Cancelable)!void {
        assert(!lookup_dns.done);
        const t = lookup_dns.threaded;
        defer t.dl.DnsFree.raw.?(lookup_dns.results.pQueryRecords, .RecordList);
        if (lookup_dns.results.QueryStatus != .SUCCESS) return;
        const t_io = t.io();
        var record_it = lookup_dns.results.pQueryRecords;
        while (record_it) |record| : (record_it = record.pNext) switch (record.wType) {
            else => {},
            .A => try lookup_dns.resolved.putOne(t_io, .{
                .address = .{ .ip4 = .{ .bytes = record.Data.A, .port = lookup_dns.options.port } },
            }),
            .AAAA => {
                const ip6: net.Ip6Address = .{
                    .bytes = record.Data.AAAA,
                    .port = lookup_dns.options.port,
                };
                try lookup_dns.resolved.putOne(t_io, .{
                    .address = if (lookup_dns.options.family) |_| .{ .ip6 = ip6 } else .fromIp6(ip6),
                });
            },
        };
        if (lookup_dns.results.pQueryRecords) |record| {
            if (lookup_dns.options.canonical_name_buffer) |buf| {
                const name_wtf16 = std.mem.span(
                    @as([*:0]const windows.WCHAR, @ptrCast(@alignCast(record.pName))),
                );
                const len = std.unicode.wtf16LeToWtf8(buf, name_wtf16);
                try lookup_dns.resolved.putOne(t_io, .{
                    .canonical_name = .{ .bytes = buf[0..len] },
                });
            }
        }
    }
}