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

[Lei Li <lilei@linux.vnet.ibm.com>]

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 <lilei@linux.vnet.ibm.com>
>> ---
>>   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