[gtkada] configuration files

[Preben Randhol]

"Ebert, Rolf" <rolf.ebert at bms.de> wrote on 29/05/2002 (15:29) :
> I think we should split the discussion into two areas:
> 
> A) functionality that has to be provided to clients of the package B)
> file (database) format of the actual configuration file
> 
> Defining the functionality (A) leads to the design of a specification
> file.
> 
> Defining the file format (B) defines the requirements for the
> implementation of the body.
> 
> Some of the requirements for A:
> 
> A.1: The underlying file format shall not be implied by the spec file

That is ok.

> A.2: A hierarchy of keys shall be possible Note: The top level
> hierarchy is usually called section by now.

Please give an example

> 
> A.3: Multiple levels of hierarchy are preferable (I do not think that
> there is consensus on this one)

You mean sections inside sections? Is this needed?

> A.4: All values shall be accessible as strings at least

Yes, Strings.
> A.5: A list of keys available in a given section shall be retrievable

Yes.

> A.6: others...
> 
> I do not like the idea to write values back to a configuration file.
> I would place the writing routines in  child package or leave them out
> completely.

You mean that one should only be able to read config files? I would like
to use the package to write the config files too. Then I know that the
config file gets correct.

What about that the package reads only one section at a time? Of course
this can be a problem if it is allowed to have an arbitrary order of the
sections.

> 
> Notes on B:

> I think we can write multiple bodies for the different file formats.
> I can even imagine a heursitic that at least the reading routines
> detect the file format automatically.

Why? It leads only to confussion on the syntax of a programs config file
It would be nice if all Ada program have the same config file format.
Besides at least I would like the package as small as simple as
possible.

> I like the idea of the 
> 
>    Section "Directory" EndSection
> 
> format.  This looks quite similar to Ada itself.  Is it possible to
> have nested sections.  How do they look like? 

Section "Screen"
        Identifier "Default Screen"
        Device     "Generic Video Card"
        Monitor    "Generic Monitor"
        DefaultDepth      16
        SubSection "Display"
                Depth     1
                Modes    "1024x768"
        EndSubSection
        SubSection "Display"
                Depth     4
                Modes    "1024x768"
        EndSubSection
EndSection

I would though prefer:

Section "Screen"
   Identifier  =  "Default Screen"
   Device      =  "Generic Video Card"
   Monitor     =  "Generic Monitor"

etc...

to distinguish keyword and value better.

> As an aside: has anybody looked at the file format for the gnat
> project files as of gcc-3.1.  This is almost pure Ada!

No, can you show an example here?

-- 
Preben Randhol ------------------- http://www.pvv.org/~randhol/ --
                 «For me, Ada95 puts back the joy in programming.»