Re: Java's System.currentTimeMillis() to C++

"Victor Bazarov" <>
Fri, 28 Sep 2007 12:09:04 -0400
<fdj8uv$37u$> wrote:

On Sep 28, 9:33 am, "Victor Bazarov" <> wrote:

tak wrote:

I have a client / server application, which the client will send the
server a timestamp everytime when there is a transaction. The client
is using Java, and it sends the timestamp using java's
System.currentTimeMillis(), which returns, "the difference, measured
in milliseconds, between the current time and midnight, January 1,
1970 UTC."

On the server side - it is implemented in C++, so, with this number
of millis since 1/1/1970 - what C++ function can I use to get the
month, day, year, hour, minute, seconds, and milliseconds?

There is no standard function that would do that. You need to look
up time/date functions provided by your OS. It is possible that it
does not have it either and you're going to have to implement it
yourself using available functions.

What about gmtime(time(NULL))? That will return a pointer to a
structure with all the information you need except milliseconds. From
there, it'd be relatively easy to do some math to get one value like
Java does, just faking the milliseconds part or using some platform-
specific function to retrieve it.

I believe that's what I meant by "have to implement it yourself". The
OP didn't specify whether milliseconds were important. The available
functions are undoubtedly described in the manual, including 'gmtime'
and 'time'. So, with additional information OP decided not to share,
I am sure all this stuff is figure-out-able.

Consider, however, that since 'gmtime' returns a pointer to some
static struct somewhere, it's not thread-safe, and special precautions
have to be made when using it on the server side, which is most likely
be threaded.

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