I take it your wrapper doesn't know just what Csound the user has installed, 
but it needs to use whatever is there, float or double, or whatever version.

About csoundCore.h, you just need to use namespaces:

namespace csoundFloat {
#include 
};
namespace csoundDouble {
#include 
};

The same thing works with different versions, too.

Then you do this:

int mycallback(void *csound,...)
{
   if (sizeof(*csound) == sizeof(csoundDouble::CSOUND))
{
    csoundDouble::CSOUND *doubleCsound = (csoundDouble::CSOUND *)csound;
} else {
}
}

And so on.... Your questions are good, but this is doable.

Regards,
Mike
----- Original Message ----- 
From: "Andy Fillebrown" 
To: "Developer discussions" 
Sent: Sunday, August 23, 2009 8:05 PM
Subject: Re: [Cs-dev] how do i get host data from a dynamically loaded 
instance of csound via the c api?


>
> Are you recommending including csoundCore.h and making the CSOUND pointer 
> transparent?
>
> I was under the impression that leaving the CSOUND pointer opaque was more 
> flexible when loading the libraries dynamically, allowing users to specify 
> in the host app which csound library to use instead of having to recompile 
> and relink to a different one each time ...and AFAIK I can't resolve 
> csound->GetHostData dynamically by function name only like I can with 
> csoundGetHostData, and by being able to load and link the wrapper to the 
> Csound API library at runtime it allows users to specify not only which 
> float version of the API to use but also which release version as long as 
> the "csoundXXX" function names remained the same across releases.  Where 
> the function pointers are located in the struct alignment would then be a 
> non-issue.  If I include any particular version of csoundCore.h wouldn't I 
> lose the benefit of being able to late-bind to different versions of the 
> Csound API simultaneously?
>
>
>
> ----- "Michael Gogins"  wrote:
>> Let's say you have callback:
>>
>> int mycallback(CSOUND *csound,...);
>>
>> You have in your wrapper:
>>
>> CSOUND *floatCsound;
>> CSOUND *doubleCsound;
>>
>> Your callback is called:
>>
>> int mycallback(CSOUND *csound,...)
>> {
>>  // NOT!!!! csoundGetHostData(csound);
>>   void *myHostData = csound->GetHostData(csound);
>> }
>>
>> The CSOUND:GetHostData function is csoundGetHostData from the same
>> library as CSOUND *floatCsound or doublecsound was created from. If
>> the callback is called from the float library, the
>> CSOUND::GetHostData
>> function here is the one from the float library. If the callback is
>> called from the double library, the CSOUND::GetHostData here is the
>> one from the double library. This kind of thing is the whole reason
>> why all the API functions are members of the CSOUND structure.
>>
>> I don't get what your problem is with this -- send me your code?
>>
>> Regards,
>> Mike
>>
>> On 8/23/09, Andy Fillebrown  wrote:
>> >
>> >
>> > ----- "Michael Gogins"  wrote:
>> >> Why don't you use the existing C++ wrappers -- because of this
>> >> business of loading both the float and the double version?
>> >
>> > Yes, I'm making a Qt-based set of classes that wrap the Csound API.
>> Part of
>> > what I want to do with it involves linking to the Csound libraries
>> at run
>> > time using QLibrary instead of linking at compile time.
>> >
>> >
>> >> Are you using one wrapper for each library, or one wrapper for
>> both
>> >> libraries?
>> >
>> > One wrapper for both.
>> >
>> >
>> >> However, my real question is this. You have a CSOUND object in
>> your
>> >> wrapper, right? Then you should do this:
>> >>
>> >> void *hostData = csound->GetHostData(csound);
>> >>
>> >> Instead of this:
>> >>
>> >> void *hostData = csoundGetHostData(csound);
>> >>
>> >> The entire Csound API is stored as function pointers in the Csound
>> >> object in this way, it is already object-oriented. These pointers
>> are
>> >> of course the ones from the correct library.
>> >
>> > Yes, but I have mutltiple csound libraries loading and linking at
>> run time,
>> > and they are using the same set of static callbacks with the only
>> > differentiating argument being the CSOUND pointer passed back.
>> Since the
>> > callback could be originating from any of the libraries currently
>> loaded, I
>> > have no way of calling the correct library's "csoundGetHostData" to
>> get my
>> > wrapper classes pointer back without knowing which library the
>> CSOUND struct
>> > was allocated in ...so if I have both the single and double
>> precision
>> > versions of Csound loaded it makes any eventual call to
>> "csoundGetHostData"
>> > from inside my callback function impossible (afaik) since calling
>> the
>> > incorrect library's "csoundGetHostData" won't work if it's not the
>> library
>> > that the CSOUND struct being pointed to was created in.  I can
>> resolve and
>> > link to any one of the csoundGetHostData functions at runtime from
>> any one
>> > of the libraries currently loaded, but only one will actually return
>> the
>> > correct host data.  In contrast -- when setting up callbacks in
>> other API's
>> > I'm allowed to specify the address of any user-data via a void
>> pointer that
>> > will be passed back to the callback, in addition to any arguments
>> specific
>> > to that particular API.  This allows simplified use of the callback
>> whether
>> > the library is bound early or late.
>> >
>> >
>> >
>> ------------------------------------------------------------------------------
>> > Let Crystal Reports handle the reporting - Free Crystal Reports 2008
>> 30-Day
>> > trial. Simplify your report design, integration and deployment - and
>> focus
>> > on
>> > what you do best, core application coding. Discover what's new with
>> > Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>> > _______________________________________________
>> > Csound-devel mailing list
>> > Csound-devel@lists.sourceforge.net
>> > https://lists.sourceforge.net/lists/listinfo/csound-devel
>> >
>>
>>
>> -- 
>> Michael Gogins
>> Irreducible Productions
>> http://www.michael-gogins.com
>> Michael dot Gogins at gmail dot com
>>
>> ------------------------------------------------------------------------------
>> Let Crystal Reports handle the reporting - Free Crystal Reports 2008
>> 30-Day
>> trial. Simplify your report design, integration and deployment - and
>> focus on
>> what you do best, core application coding. Discover what's new with
>> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
>> _______________________________________________
>> Csound-devel mailing list
>> Csound-devel@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/csound-devel
>
>
> ------------------------------------------------------------------------------
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> on
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> 


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Thanks Michael,

I will consider using this solution.  I'm not sure I want the CSOUND pointer to be transparent, though, so I may stick with the hash-table solution if it doesn't impact performance that much.  Either way, knowing to bring in csoundCore.h is very helpful since it is not done that way in the examples I've browsed and had not occurred to me.

Thanks again,
~ andy.f



----- "michael gogins"  wrote:
> I take it your wrapper doesn't know just what Csound the user has
> installed, 
> but it needs to use whatever is there, float or double, or whatever
> version.
> 
> About csoundCore.h, you just need to use namespaces:
> 
> namespace csoundFloat {
> #include 
> };
> namespace csoundDouble {
> #include 
> };
> 
> The same thing works with different versions, too.
> 
> Then you do this:
> 
> int mycallback(void *csound,...)
> {
>    if (sizeof(*csound) == sizeof(csoundDouble::CSOUND))
> {
>     csoundDouble::CSOUND *doubleCsound = (csoundDouble::CSOUND
> *)csound;
> } else {
> }
> }
> 
> And so on.... Your questions are good, but this is doable.
> 
> Regards,
> Mike
> ----- Original Message ----- 
> From: "Andy Fillebrown" 
> To: "Developer discussions" 
> Sent: Sunday, August 23, 2009 8:05 PM
> Subject: Re: [Cs-dev] how do i get host data from a dynamically loaded
> 
> instance of csound via the c api?
> 
> 
> >
> > Are you recommending including csoundCore.h and making the CSOUND
> pointer 
> > transparent?
> >
> > I was under the impression that leaving the CSOUND pointer opaque
> was more 
> > flexible when loading the libraries dynamically, allowing users to
> specify 
> > in the host app which csound library to use instead of having to
> recompile 
> > and relink to a different one each time ...and AFAIK I can't resolve
> 
> > csound->GetHostData dynamically by function name only like I can
> with 
> > csoundGetHostData, and by being able to load and link the wrapper to
> the 
> > Csound API library at runtime it allows users to specify not only
> which 
> > float version of the API to use but also which release version as
> long as 
> > the "csoundXXX" function names remained the same across releases. 
> Where 
> > the function pointers are located in the struct alignment would then
> be a 
> > non-issue.  If I include any particular version of csoundCore.h
> wouldn't I 
> > lose the benefit of being able to late-bind to different versions of
> the 
> > Csound API simultaneously?
> >
> >
> >
> > ----- "Michael Gogins"  wrote:
> >> Let's say you have callback:
> >>
> >> int mycallback(CSOUND *csound,...);
> >>
> >> You have in your wrapper:
> >>
> >> CSOUND *floatCsound;
> >> CSOUND *doubleCsound;
> >>
> >> Your callback is called:
> >>
> >> int mycallback(CSOUND *csound,...)
> >> {
> >>  // NOT!!!! csoundGetHostData(csound);
> >>   void *myHostData = csound->GetHostData(csound);
> >> }
> >>
> >> The CSOUND:GetHostData function is csoundGetHostData from the same
> >> library as CSOUND *floatCsound or doublecsound was created from.
> If
> >> the callback is called from the float library, the
> >> CSOUND::GetHostData
> >> function here is the one from the float library. If the callback
> is
> >> called from the double library, the CSOUND::GetHostData here is
> the
> >> one from the double library. This kind of thing is the whole
> reason
> >> why all the API functions are members of the CSOUND structure.
> >>
> >> I don't get what your problem is with this -- send me your code?
> >>
> >> Regards,
> >> Mike
> >>
> >> On 8/23/09, Andy Fillebrown  wrote:
> >> >
> >> >
> >> > ----- "Michael Gogins"  wrote:
> >> >> Why don't you use the existing C++ wrappers -- because of this
> >> >> business of loading both the float and the double version?
> >> >
> >> > Yes, I'm making a Qt-based set of classes that wrap the Csound
> API.
> >> Part of
> >> > what I want to do with it involves linking to the Csound
> libraries
> >> at run
> >> > time using QLibrary instead of linking at compile time.
> >> >
> >> >
> >> >> Are you using one wrapper for each library, or one wrapper for
> >> both
> >> >> libraries?
> >> >
> >> > One wrapper for both.
> >> >
> >> >
> >> >> However, my real question is this. You have a CSOUND object in
> >> your
> >> >> wrapper, right? Then you should do this:
> >> >>
> >> >> void *hostData = csound->GetHostData(csound);
> >> >>
> >> >> Instead of this:
> >> >>
> >> >> void *hostData = csoundGetHostData(csound);
> >> >>
> >> >> The entire Csound API is stored as function pointers in the
> Csound
> >> >> object in this way, it is already object-oriented. These
> pointers
> >> are
> >> >> of course the ones from the correct library.
> >> >
> >> > Yes, but I have mutltiple csound libraries loading and linking
> at
> >> run time,
> >> > and they are using the same set of static callbacks with the
> only
> >> > differentiating argument being the CSOUND pointer passed back.
> >> Since the
> >> > callback could be originating from any of the libraries
> currently
> >> loaded, I
> >> > have no way of calling the correct library's "csoundGetHostData"
> to
> >> get my
> >> > wrapper classes pointer back without knowing which library the
> >> CSOUND struct
> >> > was allocated in ...so if I have both the single and double
> >> precision
> >> > versions of Csound loaded it makes any eventual call to
> >> "csoundGetHostData"
> >> > from inside my callback function impossible (afaik) since
> calling
> >> the
> >> > incorrect library's "csoundGetHostData" won't work if it's not
> the
> >> library
> >> > that the CSOUND struct being pointed to was created in.  I can
> >> resolve and
> >> > link to any one of the csoundGetHostData functions at runtime
> from
> >> any one
> >> > of the libraries currently loaded, but only one will actually
> return
> >> the
> >> > correct host data.  In contrast -- when setting up callbacks in
> >> other API's
> >> > I'm allowed to specify the address of any user-data via a void
> >> pointer that
> >> > will be passed back to the callback, in addition to any
> arguments
> >> specific
> >> > to that particular API.  This allows simplified use of the
> callback
> >> whether
> >> > the library is bound early or late.
> >> >
> >> >
> >> >
> >>
> ------------------------------------------------------------------------------
> >> > Let Crystal Reports handle the reporting - Free Crystal Reports
> 2008
> >> 30-Day
> >> > trial. Simplify your report design, integration and deployment -
> and
> >> focus
> >> > on
> >> > what you do best, core application coding. Discover what's new
> with
> >> > Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> >> > _______________________________________________
> >> > Csound-devel mailing list
> >> > Csound-devel@lists.sourceforge.net
> >> > https://lists.sourceforge.net/lists/listinfo/csound-devel
> >> >
> >>
> >>
> >> -- 
> >> Michael Gogins
> >> Irreducible Productions
> >> http://www.michael-gogins.com
> >> Michael dot Gogins at gmail dot com
> >>
> >>
> ------------------------------------------------------------------------------
> >> Let Crystal Reports handle the reporting - Free Crystal Reports
> 2008
> >> 30-Day
> >> trial. Simplify your report design, integration and deployment -
> and
> >> focus on
> >> what you do best, core application coding. Discover what's new
> with
> >> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> >> _______________________________________________
> >> Csound-devel mailing list
> >> Csound-devel@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/csound-devel
> >
> >
> >
> ------------------------------------------------------------------------------
> > Let Crystal Reports handle the reporting - Free Crystal Reports 2008
> 
> > 30-Day
> > trial. Simplify your report design, integration and deployment - and
> focus 
> > on
> > what you do best, core application coding. Discover what's new with
> > Crystal Reports now.  http://p.sf.net/sfu/bobj-july
> > _______________________________________________
> > Csound-devel mailing list
> > Csound-devel@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/csound-devel
> > 
> 
> 
> ------------------------------------------------------------------------------
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> 30-Day 
> trial. Simplify your report design, integration and deployment - and
> focus on 
> what you do best, core application coding. Discover what's new with 
> Crystal Reports now.  http://p.sf.net/sfu/bobj-july
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