John Maddock wrote:
Silex wrote:
I found out that there's already <boost/date_time/microsec_time_clock.hpp>, but on windows it uses GetSystemTimeAsFileTime().
This raises a potential issue: I don't know if GetSystemTimeAsFileTime() works at millisecond resolution like QueryPerformanceCounter() does, and I don't know if QueryPerformanceCounter() returns some kind of epoch.. the docs are rather lowly-documented on this.
Ah, I suspect there may be problems with the CPU clock changing speed with some of these timers, I'm not sure though...
The problem with GetSystemTimeAsFileTime is that it can jump an hour forward/backward as DST kicks in/out. The problem with QueryPerformanceCounter is that QueryPerformanceFrequency is not (AFAIK) required to return the same value every time. It may be CPU clock based, and a low power CPU can vary its frequency depending on load. We don't have a good TIME_MONOTONIC solution, and we really do need one for the threading library. FWIW, I have found timeGetTime pretty reliable on Windows as a monotonic time provider. It only has 1ms resolution, though.