> You can find alot occurences of this problem in WinCE world. The problem is
> the "GetSystemTime()" call, which should fill the SYSTEMTIME struct, but it
> does not, at least not the milliseconds field (which is always 0). The
> solution I used:
>
> int gettimeofday(struct timeval* tp, int* /*tz*/) {
> #if defined(_WIN32_WCE)
> /* FILETIME of Jan 1 1970 00:00:00. */
> static const unsigned __int64 epoch = 116444736000000000LL;
> static Boolean isFirstCall = True;
> static LONGLONG unixStartTime = 0;
> static DWORD firstTickCount=0;
>
> if (isFirstCall) {
>
> FILETIME fileTime;
>
> GetSystemTimeAsFileTime(&fileTime);
>
> LARGE_INTEGER date;
> date.HighPart = fileTime.dwHighDateTime;
> date.LowPart = fileTime.dwLowDateTime;
>
> unixStartTime= (date.QuadPart - epoch) / 10000000L;
>
> firstTickCount = GetTickCount();
>
> tp->tv_sec=(long)unixStartTime;
> tp->tv_usec= 0L;
>
> isFirstCall = False; // for next time
>
> } else {
> // add elapsed seconds
> tp->tv_sec= (long)unixStartTime + (GetTickCount()-firstTickCount)/1000;
> tp->tv_usec=(GetTickCount()-firstTickCount)%1000 * 1000;
> }
>
> #else
Correction: On further thought, I don't want to make this change 'as is'. The
problem is that it's possible for the "gettimeofday()" function to be called
concurrently from multiple threads. (This is legal for LIVE555-based systems
that use different "UsageEnvironment" and "TaskScheduler" objects for each
thread.) So, the implementation needs to be 'thread safe'. If the "if" branch
of the "if (isFirstCall)" statement gets executed concurrently by more than one
thread, then "unixStartTime" and/or "firstTickCount" might get set to bad
values.
So, please rewrite your implementation to ensure that the "if" branch of the
code (i.e., the part of the code that sets static variables) is executed only
once, even if the code is called by multiple threads. (Because this code is
for WinCE only, it's OK to use some WinCE-specific locking mechanism, if
necessary.)
(However, I'll make the change to the timestamp conversion code in the next
release of the software.)
Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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