[fpc-pascal] CreateGUID() [was Re: GUID code]

Michael Van Canneyt michael at freepascal.org
Sat May 21 15:01:33 CEST 2005

On Sat, 21 May 2005, listmember wrote:

> Michael Van Canneyt wrote:
> > It's in SubVersion. 2 demo units are in packages/extra/uuid, with
> > testprograms.
> http://svn.freepascal.org/svn/fpc/trunk/packages/extra/uuid/
> It looks OK to me, except that it may be a little more optimized
> for speed since GUIDs are CPU-expensive to begin with.

Feel free to submit patches and a testprogram to prove that your 
implementation is significantly faster :-)

> A couple of questions, wrt FPC v2.x:
> -- Is Int64 supported in all platforms?


> -- Is there a Int128 or something like it?


> When Windows was 32bit, Delphi had Int64; it's only natural
> that now we should have Int128 :-)
> -- GUID unit being in extra/uuid/, does it mean it will not
> be available in, say, Windows since Windows has a native
> call for that.
> Personally, I'd like 'OnCreateGUID : TCreateGUIDFunc = Nil;
> to be available in all platforms.

It is, sysutils is cross-platform. 

On windows the default implementation calls CoCreateGUID, 
but with OnCreateGUID you can override this behaviour.

On Linux, the default behaviour is to use the kernel 
/proc/sys/kernel/random/uuid file, and fall back.

On BSD, /dev/urandom is used to generate a random GUID

on all other platforms, the system unit random() function 
is used. 

On all platforms, the default behaviour can be changed using
the OnCreateGUID event.


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