[gambit-list] How to copy data from C world into an u8vector?

Phillip Suero philsuero at gmail.com
Fri Nov 13 09:54:13 EST 2020


Ah right - allocating an u8vector in the Scheme world is always preferable
over allocating while in the C world (via ___alloc_scmobj() right), isn't
it so?

And this is because allocating an object may involve a heap overflow
exception, a resumed allocate attempt, a garbage collection, all these
complexities are only offered by |##make-u8vector| defined in
lib/_kernel.scm, which is very much preferable to invoke in a pure Scheme
setting, is it not so

Thanks,
Phil

On Fri, Nov 13, 2020 at 11:46 AM Phillip Suero <philsuero at gmail.com> wrote:

> Dear Marc,
>
> I know if I have a ___STILL u8vector, if I have a blob in the C world, I
> can just implement a c-lambda that will memcpy() that blob into the
> u8vector's memory addresses.
>
> If the u8vector is not ___STILL however, I cannot do that as the
> u8vector's memory address range could change during the memcpy(), is not
> that so.
>
> Is there any function in Gambit to copy a byte range from a fixed memory
> address into a non-___STILL u8vector?  E.g.  (u8vector-raw-copy!
> (foreign-address my-c-object) u8vector 0 length)?
>
> Or instead, is the recommendable way to do this, that I make a ___STILL
> u8vector, do memcpy() to it in a c-lambda, and then at return i
> |u8vector-copy| this u8vector, this way the resultant u8vector is
> non-___STILL which is best from the point of view of memory fragmentation?
>
> Your clarification will be much appreciated!
>
> Thanks,
> Phil
>
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