OpenEuphoria

Re: Proposal for a (small) enhancement to the value() function.

• Posted by Robert Craig <rds at RapidEuph?ria.com> Jun 29, 2007
• 723 views

CChris wrote:
> 
> Robert Craig wrote:
> > 
> > CChris wrote:
> > > I just looked at be_execute.c in this respect.
> > > 
> > > If getc() was defined as an inline function, you could remove this problem
> > > by
> > > 
> > > * having a one char buffer for each open file (handle)
> > > * having getc() to update this buffer on each read
> > > * having one excess_read flag per file which says whether a character is
> > > to
> > > be physically read from the file if clear
> > > * causing Get() (or Get2() in my version) to attempt to back up using
> > > seek()
> > > if it reads a pure number in a file as a top level object, and set the
> > > above
> > > flag using a machine_proc() interface on failure to back up
> > > * if the excess_read flag for a file is set, getc() clears it and returns
> > > the
> > > buffered char, which was read in excess. Otherwise it behaves as usual.
> > > * having where() to adjust its return value according to the excess_read
> > > status
> > > for the requested file.
> > > * having seek() to clear the flag for the file for which it is called
> > > 
> > > I am not sure whether the above can be done as getc() is a macro.
> > > And, even if it can be done, is it worth the effort, and is there any
> > > chance
> > > of a performance penalty in this sensitive area? I don't know C well
> > > enough,
> > > you probably have a clearer idea. And the final answer may depend on the
> > > compiler
> > > too.
> > 
> > I thought about adding an ungetc() several years ago,
> > but I didn't go ahead with it because:
> >   - there would be added complexity and chance of subtle bugs
> >   - Watcom had a bug in this area
> >   - no one had ever asked for it
> >   - there would be a tiny loss of performance
> > 
> > Regards,
> >    Rob Craig
> >    Rapid Deployment Software
> >    <a href="http://www.RapidEuphoria.com">http://www.RapidEuphoria.com</a>
> 
> Understandable.
> Do you think the mod above, which is a virtual ungetc() not relying on the
> compiler's
> library, and with very restricted capabilities, would be useful? At least, it
> would correct the issue of the extra space get() reads.
> I forgot to mention that EOpen() should clear the flag for the concened file.

I think it would be a rather complicated and bug-prone change.
Probably not worth the trouble. 

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com