Modifying the atoms passed to a list method
Sep 01 2019 | 9:14 am
Hi folks,
I am coding a regular Max object and I am implementing a 'list' method.
So the standard A_GIMME signature is as follows:
void myobject_list(t_myobject *x, t_symbol *sym, long argc, t_atom *argv);
In the method implementation am I allowed to do something like the following?
void myobject_list(t_myobject *x, t_symbol *sym, long argc, t_atom *argv)
{
for (long i = 0; i < argc; i++) {
double f = atom_getfloat(argv + i);
f = CLAMP(f, 0.0, 1.0);
atom_setfloat(argv + i, f);
}
outlet_list(x->outlet, NULL, argc, argv);
}
My concern comes from the fact that I am directly modifying the content of the atoms passed to the method and I am not sure if that preserves the integrity of the message passing system.
The alternative would be to make a copy of the atoms and modify the copy:
void myobject_list(t_myobject *x, t_symbol *sym, long argc, t_atom *argv) { t_atom temp[OBEX_UTIL_MAX_ATOM_STATIC]; t_atom *argv2 = atom_dynamic_start(temp, OBEX_UTIL_MAX_ATOM_STATIC, argc); for (long i = 0; i < argc; i++) { double f = atom_getfloat(argv + i); f = CLAMP(f, 0.0, 1.0); atom_setfloat(argv2 + i, f); } outlet_list(x->outlet, NULL, argc, argv2); atom_dynamic_end(temp, argv2); }
The absence of a const qualifier on the t_atom * argument suggests that I am allowed to modify the data, however since the Max API is not always consistent with regards to const-ness, I thought I would just ask.
I built a simple test case and everything seems to work as expected with both approaches, however I don't know if in a more complex situation I would encounter unexpected bugs.
So, is there a correct way to implement the above or are the two approaches equivalent?
Thanks
- Luigi
- Sep 02 2019 | 9:09 amYou are allowed but probably shouldn't ;-)Consider a patch like bellow, if vexpr didn't copy the list before doing the math, you would have strange results coming out the second (right) vexpr.
