[fpc-pascal] os dependency with ifdef

[Marc Santhoff]

Am Freitag, den 17.03.2006, 11:11 +0100 schrieb Tomas Hajny:
> Marc Santhoff wrote:
> 
> 
> Hi,
> 
> > I' like to know how I should write code for different system. SInce I'm
> > no Linux user nor have any experience on MacOS I need to know how to
> > wrap platform dependant code.
> >
> > Since I'm still fiddling with reading the serial port I have the idea
> > that linux and even MacOS may be very similar to my main os FreeBSD.
> >
> > I do know Win32 is different, but how similar are the other os'ses?
> >
> > Is there any code in the FCL or the like I can study for getting my
> > ifdefs right?
> 
> If you really want to create it prepared for current and future platforms,
> don't do it via IFDEFs first of all. The procedural solution would be to
> design a logical layer for functionality you need (get permissions for
> accessing port, open port, set characteristics, read data, write data,
> close port) in common interface part of a unit created as an include file,
> possibly create (an)other include file(s) with shared parts of the
> implementation too and create standalone units for the different platforms
> you need to support.

This is what I'm beginning to do at the moment, after some information
retrieval about how serial ports on Win32 work I've come to the
conclusion that porting the unit rtl/unix/serial.pp would be the best
thing for my special task.

I'm only bothered by the design of that stuff, no result codes
(procedure not function) in some important areas. But I will not make
changes breaking old code, I hope some exception throwing will do ... 

> Alternative solution (slightly more OOP-like and, somewhat easier to
> implement and providing more flexibility) is to use create a "manager"
> record for your particular functionality - see e.g. the heap management
> and thread management routines, plus keyboard, mouse and video management
> provided in units of the same name.

Yes, if I had to design it from the start I would think about making it
a really universally usable and technically perfect solution. But for
now my goal is to get some very simple communication running on windows
(slow, no handshake).

Thanks,
Marc