Re: [Chicken-users] call Chicken Scheme from C and pass a bytevector

[Dan Leslie]

There's a section on accessing external objects that covers this sort of 
thing:
http://wiki.call-cc.org/man/4/Accessing%20external%20objects#returning-large-objects-or-chunks-of-memory-to-scheme

It's possible to allocate C structures under the control of the Chicken GC:
http://wiki.call-cc.org/allocating-c-structures-under-control-of-the-chicken-gc

However, you can also leave control up to the user rather than the GC 
and they can use free:
http://api.call-cc.org/doc/lolevel/free

Personally, I like to allocate blobs and  srfi-4 vectors in scheme and 
pass them as parameters to C functions to be mutated.

-Dan

On 6/27/2013 10:07 AM, Claude Marinier wrote:
> Hi,
>
> A function in pcap-interface.c calls Chicken Scheme. It builds a 
> vector containing a bunch of things, e.g. C_fix(ethtype), and the 
> source and destination addresses as vectors. The scheme code converts 
> the address vectors to u8vector (u16vector for IPv6). This is a lot of 
> work: just under 20% of CPU time is spent in vector->u8vector.
>
> If I could create a blob in C and pass it to scheme, the scheme code 
> could use blob->u8vector/shared and blob->u16vector/shared which would 
> achieve the same result with much less work.
>
> What is the recommended way to pass a blob to scheme from C?
>
> Is there a way to create a u8vector or u16vector directly in C?
>
> Thank you.