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.]
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