timeoutToWindowsInterval

fn timeoutToWindowsInterval(timeout: Io.Timeout) ?windows.LARGE_INTEGER {
    // ntdll only supports two combinations:
    // * real-time (`.real`) sleeps with absolute deadlines
    // * monotonic (`.awake`/`.boot`) sleeps with relative durations
    const clock = switch (timeout) {
        .none => return null,
        .duration => |d| d.clock,
        .deadline => |d| d.clock,
    };
    switch (clock) {
        .cpu_process, .cpu_thread => unreachable, // cannot sleep for CPU time
        .real => {
            const deadline = switch (timeout) {
                .none => unreachable,
                .duration => |d| nowWindows(clock).addDuration(d.raw),
                .deadline => |d| d.raw,
            };
            const epoch_ns = std.time.epoch.windows * std.time.ns_per_s;
            return @intCast(@max(@divTrunc(deadline.nanoseconds - epoch_ns, 100), 0));
        },
        .awake, .boot => {
            const duration = switch (timeout) {
                .none => unreachable,
                .duration => |d| d.raw,
                .deadline => |d| nowWindows(clock).durationTo(d.raw),
            };
            return @intCast(@min(@divTrunc(-duration.nanoseconds, 100), -1));
        },
    }
}