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time_t to TDateTime

 
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tinyabs
Guest
PostPosted: Wed Oct 12, 2005 12:15 pm    Post subject: time_t to TDateTime Reply with quote


How do I convert a time_t to a TDateTime? I try
TDateTime::FileTimeToDateTime() but it fails.


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Steve Aletto
Guest
PostPosted: Wed Oct 12, 2005 2:44 pm    Post subject: Re: time_t to TDateTime Reply with quote


Quote:
How do I convert a time_t to a TDateTime? I try
TDateTime::FileTimeToDateTime() but it fails.

One way:

TDateTime timet2datetime(const time_t t)
{
TDateTime rv;
struct tm *stm = localtime(&t);
if (stm)
{
rv = TDateTime(stm->tm_year + 1900, stm->tm_mon + 1,
stm->tm_mday);
rv += TDateTime(stm->tm_hour, stm->tm_min, stm->tm_sec,
0);
}
return(rv);
}

I think this is not thread-safe. Furthermore, it introduces a
memory leak due to localtime(), but I don't know whether it can
be solved.

Steve.



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tinyabs
Guest
PostPosted: Wed Oct 12, 2005 3:00 pm    Post subject: Re: time_t to TDateTime Reply with quote


Is time_t is dosdatetime type? I got this type from Win32's IpHelper. If it
is, I can write a function to extract the date and time.


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Bob Gonder
Guest
PostPosted: Wed Oct 12, 2005 3:22 pm    Post subject: Re: time_t to TDateTime Reply with quote
Steve Aletto wrote:

Quote:
struct tm *stm = localtime(&t);
if (stm)
{..... }
return(rv);

I think this is not thread-safe. Furthermore, it introduces a
memory leak due to localtime(), but I don't know whether it can
be solved.

Not a leak...
"localtime returns a pointer to the structure containing the time
elements. This structure is a static that is overwritten with each
call."
One might assume that the multithread version of the libs store the
struct in thread local storage.

But you might want to give rv a default value if localtime fails.



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Steve Aletto
Guest
PostPosted: Wed Oct 12, 2005 3:29 pm    Post subject: Re: time_t to TDateTime Reply with quote
Quote:
Is time_t is dosdatetime type? I got this type from Win32's
IpHelper. If it is, I can write a function to extract the date
and time.

time_t is a long integer:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_CRT_Standard_Types.asp

Steve.



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Steve Aletto
Guest
PostPosted: Wed Oct 12, 2005 3:33 pm    Post subject: Re: time_t to TDateTime Reply with quote
Quote:
Not a leak...

That's what I thought as well, but CodeGuard signals it...

Quote:
But you might want to give rv a default value if localtime
fails.

The TDateTime's contructor already gives a default value to rv:
"when called with no arguments, the resulting TDateTime object
has a Val data member of zero. This date and time corresponds to
12/30/1899 12:00 am".

Steve.



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tinyabs
Guest
PostPosted: Wed Oct 12, 2005 4:09 pm    Post subject: Re: time_t to TDateTime Reply with quote
I did some findings and produced this code.
time_t is the number of seconds passed a fixed date/time.

TDateTime ToDateTime(time_t time)
{
TDateTime dt = IncSecond(EncodeDateTime(1970, 1, 1, 0, 0, 0, 0), time);
return dt;
}


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