OpenEuphoria

Re: Euphoria on DOSbox

• Posted by CChris <christian.cuvier at agriculture.?o?v.fr> Oct 30, 2007
• 834 views

Robert Craig wrote:
> 
> CChris wrote:
> > Really?
> > The code in be_machine.c has some interrupt #31 calls which are specific to
> > Causeway according to RBIL v61:
> > * long_to_short(): AX=#FF21 (GetMemDOS) and #FF01 (RM interrupt)
> > * InitGraphics(): AX=#FF08 (GetSelDet32)
> > * user_allocate_low(): AX=#FF21
> > * user_free_low: AX=#FF23 (RelMemDOS)
> > * dos_interrupt: AX=#FF01
> > 
> > So... I expect these areas of the backend source will require some
> > alternative
> > variant selected by an #ifdef ... #else directive.
> 
> Thanks for spotting those calls. They are specialized bits
> of code you would probably have to change to 
> achieve 100% compatibility, but I think the bulk of 
> Euphoria for DOS should work OK without any source code changes. 
> For instance, Bernie recently said he got pmodew working:
> 
>    <a
>    href="http://www.openeuphoria.org/EUforum/m17215.html">http://www.openeuphoria.org/EUforum/m17215.html</a>
> 
> I switched over to the Causeway DOS extender,
> from DOS4GW, more than a decade ago.
> I compared against a couple of other DOS extenders at that time.
> I recall that things pretty much worked immediately, 
> without any source changes, whichever extender I used.
> Though, as you observe, I did eventually code a few
> Causeway-specific calls to support some tricky stuff,
> such as the Euphoria dos_interrupt() library routine etc.
> 
> Regards,
>    Rob Craig
>    Rapid Deployment Software
>    <a href="http://www.RapidEuphoria.com">http://www.RapidEuphoria.com</a>

Looking at the docs, you may even be able to drop Causeway specific calls
altogether:
* replace #FF21 by #0100 (DPMI DOS allocate)
* replace #FF23 by #0101 (DPMI DOS free)
* replace #FF01 by #0300 (DPMI perform real mode interrupt)
* replace #FF08 by #0006 (DPMI get descriptor linear addr)

The (slightly) tricky bit is at line 574, which would have to be edited as:

peekaboo = ((regs.x.ecx && 0xFFFF)<<16)+(regs.x.edx && 0xFFFF);    // base of
selector

I didn't find the definition for the REGS union - don't have a C compiler here
-, so this line can probably be simplified by using the 16 bit register version
only, since the base addr is returned in CX:DX instead of EDX.

I didn't check whether the real mode call structures standard DPMI and CauseWay
use are the same; I'd be surprised if they are not. Otherwise, register usage is
consistent, so nothing else needs any change, since nothing else in the source
depends on the extender.

CChris