Re: [B2-devel] [patch] Port SheepShaver's precise timer to OS X

[Alexei S. <ale...@gm...>]

Committed. Thanks.

-Alexei

On Mon, Aug 17, 2009 at 3:29 PM, Charles
Srstka<bas...@ch...> wrote:
> Attached is a set of patches to port the precise timer that is currently
> used in the Linux and BeOS builds of SheepShaver to Mac OS X (and any other
> Mach-based operating systems).
>
> Currently, the Linux build uses the clock_gettime() function to get
> nanosecond-precision time, and falls back on gettimeofday() if it is not
> present. Unfortunately, Mac OS X does not currently support clock_gettime(),
> and gettimeofday() has only microsecond granularity. The Mach kernel,
> however, has a clock_get_time() function that does very nearly the same
> thing as clock_gettime(). The patches to BasiliskII cause the timing
> functions such as timer_current_time() to use clock_get_time() instead of
> gettimeofday() on Mach-based systems that do not support clock_gettime().
>
> The changes to SheepShaver involve the precise timer. The existing code for
> Linux uses pthreads and real-time signals to handle the timing. Mac OS X
> unfortunately does not seem to support real-time signals, so Mach calls are
> again used to suspend and resume the timer thread in order to attempt to
> duplicate the Linux and BeOS versions of the timer. The code is somewhat
> ugly right now, as I decided to leave alone the pre-existing style of the
> source file, which unfortunately involves #ifdefs scattered throughout the
> file and some duplication of code. A future patch may want to clean this up
> to separate out the OS-specific code and put it all together at the top of
> the file. However, for the time being, this seems to work.
>
> This has not been extensively tested, because I have not been able to get my
> hands on a good test-case app for the classic Mac OS that would run inside
> the emulator and try out the timer. However, performance does seem to be
> better than with the pre-existing code, and nothing seems to have blown up
> as far as I can tell. I did find a game via a Google search -  Cap'n Magneto
> - that is known to have problems with Basilisk/SheepShaver's legacy 60 Hz
> timer, and the opening fade-to-color for this game appears to run much more
> smoothly with the precise timer code in place.
>
> I hope that you find these patches satisfactory.
>
>
>
>
> Charles
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