www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - d_time2FILETIME

reply Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
Hello,

I want to port the function setFileTimes available in Phobos/Posix to 
Windows. Does anyone know of a simple way to convert a d_time value to a 
FILETIME value? d_time is Ticks since 1-1-1970 and FILETIME contains 
quanta of 100-nanoseconds since 1-1-1601. So there's only some shifting 
and scaling involved, but the shifting constant is tricky :o).

Andrei
Apr 10 2009
next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Fri, 10 Apr 2009 18:07:20 +0400, Andrei Alexandrescu
<SeeWebsiteForEmail erdani.org> wrote:


 Hello,

 I want to port the function setFileTimes available in Phobos/Posix to  
 Windows. Does anyone know of a simple way to convert a d_time value to a  
 FILETIME value? d_time is Ticks since 1-1-1970 and FILETIME contains  
 quanta of 100-nanoseconds since 1-1-1601. So there's only some shifting  
 and scaling involved, but the shifting constant is tricky :o).

 Andrei


You may take a look at Boost Posix Time System:
http://www.boost.org/doc/libs/1_38_0/doc/html/date_time/posix_time.html

It has a plenty of functions that convert time to and from various formats,
including Posix time and Windows FILETIME.
Apr 10 2009
prev sibling parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Fri, 10 Apr 2009 10:07:20 -0400, Andrei Alexandrescu  
<SeeWebsiteForEmail erdani.org> wrote:


 Hello,

 I want to port the function setFileTimes available in Phobos/Posix to  
 Windows. Does anyone know of a simple way to convert a d_time value to a  
 FILETIME value? d_time is Ticks since 1-1-1970 and FILETIME contains  
 quanta of 100-nanoseconds since 1-1-1601. So there's only some shifting  
 and scaling involved, but the shifting constant is tricky :o).


What you need is the constant that is the number of Ticks (either 100ns  
ticks or whatever) from 1601 to 1970.

I redid most of the tango time stuff, but those constants were already  
there before my time (no pun intended).  The number of seconds between  
1/1/1601 and 1/1/1970 is 11644473600.  Scale that to whatever you wish.

Note that we do not take into account leap-seconds, not sure if that  
matters to you.

-Steve
Apr 10 2009
parent reply Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
Steven Schveighoffer wrote:

 On Fri, 10 Apr 2009 10:07:20 -0400, Andrei Alexandrescu 
 <SeeWebsiteForEmail erdani.org> wrote:
 

 Hello,

 I want to port the function setFileTimes available in Phobos/Posix to 
 Windows. Does anyone know of a simple way to convert a d_time value to 
 a FILETIME value? d_time is Ticks since 1-1-1970 and FILETIME contains 
 quanta of 100-nanoseconds since 1-1-1601. So there's only some 
 shifting and scaling involved, but the shifting constant is tricky :o).


 
 What you need is the constant that is the number of Ticks (either 100ns 
 ticks or whatever) from 1601 to 1970.
 
 I redid most of the tango time stuff, but those constants were already 
 there before my time (no pun intended).  The number of seconds between 
 1/1/1601 and 1/1/1970 is 11644473600.  Scale that to whatever you wish.
 
 Note that we do not take into account leap-seconds, not sure if that 
 matters to you.
 
 -Steve


Thanks a lot! However, something's amiss a bit. I have this code:

     static d_time FILETIME2d_time(const FILETIME *ft)
     {
         SYSTEMTIME st = void;
         if (!FileTimeToSystemTime(ft, &st))
             return d_time_nan;
         return SYSTEMTIME2d_time(&st, 0);
     }

     FILETIME d_time2FILETIME(d_time dt)
     {
         enum ulong ticksFrom1601To1970 = 11_644_473_600UL * TicksPerSecond;
         static assert(10_000_000 % TicksPerSecond == 0);
         ulong t = (dt - ticksFrom1601To1970) * (10_000_000 / 
TicksPerSecond);
         FILETIME result = void;
         result.dwLowDateTime = cast(uint) (t & uint.max);
         result.dwHighDateTime = cast(uint) (t >> 32);
         return result;
     }

     unittest
     {
         auto dt = getUTCtime;
         auto ft = d_time2FILETIME(dt);
         auto dt1 = FILETIME2d_time(&ft);
         assert(dt == dt1, text(dt, " != ", dt1));
     }

which fails with 1239379868629 != 156195960030165. Let me clarify that a 
little:

1_239_379_868_629 != 156_195_960_030_165

So it looks like I made a mistake somewhere because the difference is 
very large. A FILETIME has 100-ns increments, and there are 10_000_000 
of those in a second. So I get the ticks from 1601 to dt, then I divide 
by TicksPerSecond to get the seconds, and finally I multiply by 10M to 
get the 100-ns count. Where am I wrong?


Thanks,

Andrei
Apr 10 2009
parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
Andrei Alexandrescu wrote:

         ulong t = (dt - ticksFrom1601To1970) * (10_000_000 / 
 TicksPerSecond);


That must be addition, otherwise I go back in time to 1200 or so. Now 
everything works, thanks to all who answered. The upside of all this is 
that now setFileTimes works on both Windows and Posix. :o)

Andrei
Apr 10 2009