[fpc-pascal] Microsecond Delay Suggestions?

[Sven Barth]

On 26.07.2016 21:52, James Richters wrote:
>> An alternative would be NtDelayExecution from unit jwanative. Its interval
> argument is in multiples of 100ns
>> and is essentially what Windows' Sleep() uses internally.
>> Note: The first argument "Alertable" determines whether the function can be
> interrupted by NtAlertThread 
>> (and whatever Windows API functions use that internally).
> 
> This sounds like it would work, but I can't figure out how to use it.  Do
> you have an example?  
> I've tried just a quick test like this:
> 
> uses
>   windows,jwanative;
> Var
>   DelayInterval : PLarge_Integer;
>   Variable1:integer;
> begin
> DelayInterval:=1;
> Variable1:=NtDelayExecution(true,DelayInterval);
> end.
> 
> It won't let me set DelayInterval with a constant, I get "Incompatible
> Types: got "shortint" expected "Plarge_Integer"  
> I really don't undertand these variable types that it wants.  

You need to declare a LargeInteger and pass the pointer to it to
NtDelayExecution(). LargeInteger itself is declared as a case-record
consisting of two 32-bit values (LowPart and HighPart) and a 64-bit
value (QuadPart). Best is you assign your value to QuadPart, as that
sets the record in one go.
Oh and I forgot to mention that you need to use a negative value for
relative sleeps (otherwise you'll wait until that time from the system
start on has passed, so "1" would be a no-op basically ;) )

For an example see the implementation of Sleep in the SysUtils unit of
the NativeNT target: rtl/nativent/sysutils.pp (near the end of the file)

Regards,
Sven