Re: interfacing with c - unification of pointers to structures

Hello,

since gprolog ints are not coded on signed 29 bits it is difficult to
ensure you can encode a pointeur as a Prolog integer. Some possible
solutions:

- encode an index (0-based displacement). If not possible, use an
array in C where you store the pointer then you pass the index inside
this array

- encode it as a Prolog float (C double).

- encode it as a Prolog structure of 2 integers (2 x 16 bits)

- encode it as an atom (only if there is a limited set of pointers
to handle).

Daniel

Tushar Parekh a écrit :

hello,

i have interfaced gnu prolog and c libraries.

i am able to handle input, output arguments of simple types like
string, integer.

i have a structure in c program e.g. BITMAP. i want to return a
pointer to this structure

i.e. BITMAP * back to gnu prolog from c function. how do i code this ?

i am working on 32 bit machine. so all pointers are 32 bits. i am
able to handle integer output

arguments by declaring int * on c function side and setting this to the
integer value and returing

PL_TRUE to enable binding to prolog argument. can i cast BITMAP * to
INTEGER * and send it

back to gnu prolog. the reason i need to store this pointer on prolog
side is to facilitate future calls

to c functions with this pointer supplied as an argument.

thank you in advance for any help.

regards,

tushar parekh.

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