Let's say you have a shared C library (called testlib.so) with the following
function signature:
void func1(int *buf);
How would you use uFFI to call this function? How would you complete the
following code fragment:
self ffiCall: #( void func1(??? buf) ) module: 'testlib.so'.
where buf should hold whatever integer value func1 puts into it. Maybe buf
needs to be prepared somehow before the ffiCall?
horrido wrote
> Je comprends enfin...
>
> I accidentally came across a StackOverflow answer that suggested the
> String object is immutable. That makes perfect sense, as I know the C
> function is actually
/*
> trying
*/
> to write to the buffer.
>
> That gave me the idea to use a ByteArray instead. Now, everything works!
>
> horrido wrote
>> There is shockingly very little documentation on how to use uFFI. In
>> particular, I have the following situation...
>>
>> A shared C lib has the following function:
>>
>> void get_machine(char *machine) {
>> uname(&uname_s);
>> strcpy(machine, uname_s.machine);
>> }
>>
>> It copies the content of a string value into the buffer passed to it
>> (char *machine).
>>
>> I want to call this function from Pharo, thus:
>>
>> buffer := String new: 64.
>> self ffiCall: #( void get_machine(String buffer) ).
>>
>> The buffer never receives the string value (it just contains the 64
>> initiialized spaces).
>>
>> Clearly, I'm misunderstanding the proper mechanism for doing this.
>>
>> [There are other functions in the shared C lib that work fine, such as:
>>
>> uint get_uptime() {
>> sysinfo(&info);
>> return info.uptime;
>> }
>>
>> Returning integers or floats is no problem. But passing arguments by
>> reference seems to be verboten.]
--
View this message in context:
http://forum.world.st/How-to-use-uFFI-with-String-tp4947890p4948184.html
Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.
