Interpreting timestamp value

[mbp]

I would like to ignore SpaceNavigator events if they are stale, however clock_get_uptime seems to be a kernel function with no userland equivalent. How do I interpret the timestamp value in a Cocoa app and compare it with the current time?

[flomotan]

You can use mach_absolute_time to get the current time. When comparing the two times, don't do an absolute equality check (i.e. time_now == event_time) as this will always fail since there will be some elapsed processing time between the event_time and time_now.

[neuronaut]

Hi all,

quick question in response to the previous posting: are you taking into account that mach_absolute_time is CPU dependent? This is not really a clock... so I am wondering if this wouldn't create problems on Intel vs. PPC Macs where mach_absolute_time behaves differently if you're relying on a constant threshold when discarding events...

Best wishes
--smb

[flomotan]

Yeah, you'd normally want to normalize the value you get back from mach_absolute_time before using it to measure elapsed time. Here's a note from apple http://developer.apple.com/qa/qa2004/qa1398.html

[davecotter]

see this thread for some actual code to answer this question:

viewtopic.php?t=3419