netWriteWindows

fn netWriteWindows(
    handle: net.Socket.Handle,
    header: []const u8,
    data: []const []const u8,
    splat: usize,
) net.Stream.Writer.Error!usize {
    if (!have_networking) return error.NetworkDown;

    var iovecs: [max_iovecs_len]windows.AFD.WSABUF(.@"const") = undefined;
    var len: u32 = 0;
    addAfdBuf(.@"const", &iovecs, &len, header);
    for (data[0 .. data.len - 1]) |bytes| addAfdBuf(.@"const", &iovecs, &len, bytes);
    const pattern = data[data.len - 1];
    var backup_buffer: [64]u8 = undefined;
    if (iovecs.len - len != 0) switch (splat) {
        0 => {},
        1 => addAfdBuf(.@"const", &iovecs, &len, pattern),
        else => switch (pattern.len) {
            0 => {},
            1 => {
                const splat_buffer = &backup_buffer;
                const memset_len = @min(splat_buffer.len, splat);
                const buf = splat_buffer[0..memset_len];
                @memset(buf, pattern[0]);
                addAfdBuf(.@"const", &iovecs, &len, buf);
                var remaining_splat = splat - buf.len;
                while (remaining_splat > splat_buffer.len and len < iovecs.len) {
                    addAfdBuf(.@"const", &iovecs, &len, splat_buffer);
                    remaining_splat -= splat_buffer.len;
                }
                addAfdBuf(.@"const", &iovecs, &len, splat_buffer[0..@min(remaining_splat, splat_buffer.len)]);
            },
            else => for (0..@min(splat, iovecs.len - len)) |_| {
                addAfdBuf(.@"const", &iovecs, &len, pattern);
            },
        },
    };

    const iosb = try deviceIoControl(&.{
        .file = .{ .handle = handle, .flags = .{ .nonblocking = true } },
        .code = windows.IOCTL.AFD.SEND,
        .in = @ptrCast(&windows.AFD.SEND_INFO{
            .BufferArray = &iovecs,
            .BufferCount = len,
            .AfdFlags = .{ .NO_FAST_IO = true, .OVERLAPPED = true },
            .TdiFlags = .{},
        }),
    });
    switch (iosb.u.Status) {
        .SUCCESS => return iosb.Information,
        .CANCELLED => unreachable,
        .INSUFFICIENT_RESOURCES => return error.SystemResources,
        .CONNECTION_RESET, .REMOTE_DISCONNECT => return error.ConnectionResetByPeer,
        .IO_TIMEOUT => return error.ConnectionTimedOut,
        else => |status| return windows.unexpectedStatus(status),
    }
}