[Lazarus] Portable way to get accurate timestamps?

[Sven Barth]

On 27.02.2011 17:51, Graeme Geldenhuys wrote:
> On 26 February 2011 20:43, Marco van de Voort<marcov at stack.nl>  wrote:
>>
>> (1) this discussion is about a gettickcount implementation, but I'm not
>> entirely sure why this is needed so badly.
>
> I am by no means a libc expert, though I have tried myself to find a
> more fine-grained timing call under Linux. Windows (and I believe the
> GetTickCount implementation for Windows) uses the higher precision
> timing calls from the multimedia API. I can't confirmed this because
> I'm not at a computer with FPC source code - but from memory I think
> that is how it was done. The current linux version of GetTickCount is
> very rudimentary. As a few Google searches will show, many other
> developers are saying that using clock_gettime() under linux gives you
> the equivalent timing as the multimedia API under Windows.

I don't know whether you stuff the GetTickCount API call under 
"Multimedia API", but the GetTickCount implementation for Windows uses 
just that.

See this snippet from lcl/lclintf.pas:

=== source begin ===
{$IFDEF WINDOWS}

{$IFDEF MSWindows}
function GetTickCount:DWORD; stdcall; external 'kernel32.dll' name 
'GetTickCount';
{$ELSE}
function GetTickCount:DWORD; stdcall; external KernelDLL name 
'GetTickCount';
{$ENDIF}

{$ELSE}
function GetTickCount: DWord;
{$ENDIF}
=== source end ===

And GetTickCount uses the data provided by the Kernel for that (I don't 
know yet how the kernel calculates that data though...)

Regards,
Sven