Re: [Qemu-devel] [PATCH 1/2] qga: add windows implementation for guest-get-time

[Lei Li]

On 03/14/2013 08:32 PM, mdroth wrote:
> On Thu, Mar 14, 2013 at 03:07:50PM +0800, Lei Li wrote:
> > Signed-off-by: Lei Li <address@hidden>
> > ---
> >   qga/commands-win32.c | 33 +++++++++++++++++++++++++++++++++
> >   1 file changed, 33 insertions(+)
> >
> > diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> > index 7e8ecb3..e24fb4a 100644
> > --- a/qga/commands-win32.c
> > +++ b/qga/commands-win32.c
> > @@ -22,6 +22,12 @@
> >   #define SHTDN_REASON_FLAG_PLANNED 0x80000000
> >   #endif
> >
> > +/* multiple of 100 nanoseconds elapsed between windows baseline
> > +   (1/1/1601) and Unix Epoch (1/1/1970), accounting for leap years */
> > +#define W32_FT_OFFSET (10000000ULL * 60 * 60 * 24 * \
> > +                       (365 * (1970 - 1601) +       \
> > +                        (1970 - 1601) / 4 - 3))
> > +
> >   static void acquire_privilege(const char *name, Error **err)
> >   {
> >       HANDLE token;
> > @@ -108,6 +114,33 @@ void qmp_guest_shutdown(bool has_mode, const char *mode, 
> > Error **err)
> >       }
> >   }
> >
> > +int64_t qmp_guest_get_time(Error **errp)
> > +{
> > +    SYSTEMTIME *ts = g_malloc0(sizeof(SYSTEMTIME));
> I still don't understand why we do just do:
>
> SYSTEM ts = {0};
>
> > +    int64_t time_ns;
> > +    FILETIME tf;
> > +
> > +    GetSystemTime(ts);
> followed by:
>
> GetSystemTime(&ts);
>
> (and same for SystemTimeToFileTime() below)
>
> This would avoid the need to add common cleanup code for all the
> return paths.
>
> > +    if (!ts) {
> this is gonna always be false since we initialize it at the start of
> this function.
>
> also, GetSystemTime() does seem to provide any error indication
> whatsoever, which is strange. But it also doesn't seem to have any
> guarantee this it will always succeed...
>
> I think the best we could do is probably just some kind of sanity
> check, like making sure ts.wYear != 0, or maybe that
> 1601 <= ts.wYear <= 30827

I was trying to check it by ts.wYear != 0 this afternoon...
OK, I will send update later as you suggested.

Thanks!

> > +        error_setg(errp, "Failed to get time");
> > +        goto out;
> > +    }
> > +
> > +    if (!SystemTimeToFileTime(ts, &tf)) {
> > +        error_setg_errno(errp, errno, "Failed to convert system time");
> > +        goto out;
> > +    }
> > +
> > +    time_ns = ((((int64_t)tf.dwHighDateTime << 32) | tf.dwLowDateTime)
> > +                - W32_FT_OFFSET) * 100;
> > +
> > +    return time_ns;
> > +
> > +out:
> > +    g_free(ts);
> > +    return -1;
> > +}
> > +
> >   int64_t qmp_guest_file_open(const char *path, bool has_mode, const char 
> > *mode, Error **err)
> >   {
> >       error_set(err, QERR_UNSUPPORTED);
> > --
> > 1.7.11.7


--
Lei