malloc-free allocation (was: FFI guru/wizard award to be rewarde d)

Hoehle, Joerg-Cyril writes:

 > >I also wrote a thin C wrapper around DB functions, since it is
 > Do you believe you would have written a CLISP module if you
 > had known about my article earlier?

well, I have written a module!

 > One of my points is that writing FFI+C code is half the way of a
 > writing module, *and* writing modules prevents you from the
 > CAST/TYPECASE madness.

why? OK, if it is explained in your article I'll try to find it.

 > OTOH, you need to be more confident with CLISP's C-level functions,
 > e.g. allocate_string() etc.

which are not documented :(

 > >impossible to use DB structure and its function pointers from Lisp:
 > I guess one of your points is that the functions to be called are
 > like db->get(), i.e. there's nothing with a fixed name like
 > "BDB_get()". This looks like instance methods -- not impossible,
 > but possibly impractical.  I never thought about these, but they
 > are conceptually close to shared-library functions: they hang of
 > the library, here the DB pointer.
 > 
 > Is there anything else which makes you feel that it's impossible?

no. Initially my idea was to define a Lis DB type using def-c-struct
and faithfully translate all the C struct members into Lisp slots. A
nightmare: DB has tens of members! Furthermore, it is probably better
to keep DB and other BDB C structures opaque to Lisp. There is no need
to make implementation details, such as structure members, available
at Lisp level.

 > Why don't you use something along
 >  (typecase
 >   ((unsigned-int 32)
 >    (values 'int/uint32 (FFI:sizeof 'int-or-uint32))
 >   ((signed-int 32) (values 'sint32 (sizeof 'sint32))
 >   ... Constant-folding by hand?
 > Fixnum can be pretty small (i.e. only 24 bits).

yes, I know. I'm going to add more integer subtypes later.



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