Re: Import a type from C

["chris.danx" <chris.danx@ntlworld.com>]

Francisco Santoyo wrote:

 > Hi
 >
 > I have to use a type struct, which is defined in a C library. Anybody
 > know,
 > how can I import that type from C to Ada?
 >
 > Thanks.


As far as I'm aware you can't import a "type", but you can declare an
equivalent type and import variables of that type into Ada.  i.e. you
can't import the type X, only variables of type X.

struct myStruct {
    int x;
    int y;
    char *str;
};

would go to an Ada record

type myStruct is record
     x : integer;
     y : integer;
     str : blah -- haven't done this in a while.
end record;


The details are a little sketchy as I've been programming in Java for
two, maybe three months now (my knowlege of Ada is evaporating :( ), but
structs in C rougly correspond to records in Ada, C strings to Char_Ptr,
etc.  Of course, some of this depends on the compilers involved too, so
there's some variation.

What I would be inclined to do in the case of Strings would be to
convert C strings to proper Ada Strings, if I was going to use them in
Ada code and no more in C code (if you need to send them back, you have
to consider a tradeoff between the convienance of Ada strings and the
conversion between the two forms - which costs time).

The lovelace tutorial has some text on interfacing with C, which maybe
worth a look (it's a much better description than my pitiful attempt, so
you *should* read it to unconfuse yourself after reading my post :)  I
have a habit of doing stuff like that).  There's a link to it from
www.adapower.com iirc.


hth,
Danx
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