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From: dmitry@elros.cbb-automation.de (Dmitry A. Kazakov)
Newsgroups: comp.lang.ada
Subject: Re: FILETIME <-> Ada.Real_Time.Time conversions
Date: Wed, 19 Dec 2001 13:37:28 GMT
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Date: 2001-12-19T13:37:28+00:00
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On Wed, 19 Dec 2001 10:02:39 +0100, Alfred Hilscher
<Alfred.Hilscher@icn.siemens.de> wrote:

>On WinXX I would first convert FileTime to SystemTime (which is more
>appropriate).
>
>BOOL FileTimeToSystemTime(
>
>    CONST FILETIME *  lpFileTime,	// pointer to file time to convert 
>    LPSYSTEMTIME  lpSystemTime 	// pointer to structure to receive
>system time  
>   );	

Actually FILETIME [UTC] format is used in a communication protocol to
represent time-stamps. Win32 SYSTEMTIME is rougly same though with
great precision loss, because its resolution is 1ms.

It seems that under Win32 there is no way to convert FILETIME to the
high-resolution monotonic time (performance counters) . Therefore a
complicated statistical algorithm was implemented to convert FILETIME
to performance counters (in C++). This way is well possible, but time
consuming, unreliable and of course depends on Win32 API.

Presently parts of the system are under implementation in Ada 95 *not*
under Win32. There is no designated platform. It should be portable.
So the question reappears. It is relatively easy to convert FILETIME
to Ada.Calendar.Time provided that Ada.Calendar.Split and Time_Of are
dealing with UTC [??]. Yet there is a hint in Ada Rationale that
Ada.Calendar.Time might suffer jumps because of daylight savings
[shudder]. At the same time, it seems that Ada.Real_Time.Time was very
carefully designed to prevent any attempt to correlate it with any
external clock [??]. So the problem.

Regards,
Dmitry Kazakov