For special pointer types there's less worry about data unit sizes and so on; you just get the byte array's start offset and the (U|S)(8|16|32)vector contents follow in one block after this.

2013/4/12 Álvaro Castro-Castilla <alvaro.castro.castilla@gmail.com>

Thanks, Mikael.

If you use Car, Cdr, etc from C, you are actually at the same point, traversing the structure. That's fine for lists, but what about vectors?
I would like to use memcpy, but for that:
- i must respect alignment, padding or chunks if they happen to exist in Gambit's vectors implementation.
- i must know the array pointer, in case is stored after some Gambit-specific data, such as type tags.

Thanks again for your answer,

Álvaro

El 12/04/2013 12:37, "Mikael" <mikael.rcv@gmail.com> escribió:

Hi Alvaro,

You can traverse all Scm structures from C.

You have typecheckers, car, cdr, vector-ref, accessors for all the specialized vector types and so on.

In the current Gambit version, from all I know, using these works perfectly.

As soon as Gambit goes SMP, this may be a slightly other story and only the objects specifically allocated with ___STILL may be safe to use, we'll see when we get there. What could be an issue would be that the GC would trig during your C call and change all the other object references to an object and then its physical memory location, and you'd be using the old one in your C code.

Do you have a specific question or problem to solve?

Brgds,
Mikael

2013/4/12 Álvaro Castro-Castilla <alvaro.castro.castilla@gmail.com>

There is one thing that I've been meaning to ask for a long time now.

I see most of the people tend to create arrays in C by malloc/___alloc_rc and then assigning values by iterating over them via a setter function (also defined with c-lambda).

Isn't there a way to directly do this with a memcpy operation? Wouldn't that be faster?

I understand that Gambit's heap and C's heap are separate, and you need to copy from one another in order to avoid GC touching any of FFI-created memory. But is it possible to improve this process using some sort of C function/macro from Gambit?

I really can't find any code examples or reference for this.

Thank you very much.

Álvaro

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