Question

From the reading that I have done, Core Audio relies heavily on callbacks (and C++, but that’s another story).

I understand the concept (sort of) of setting up a function that is called by another function repeatedly to accomplish a task. I just don’t understand how they get set up and how they actually work. Any examples would be appreciated.

Answer 1

There is no ‘callback’ in C – not more than any other generic programming concept.

They’re implemented using function pointers. Here’s an example:

void populate_array(int *array, size_t arraySize, int (*getNextValue)(void)) {     for (size_t i=0; i<arraySize; i++)         array[i] = getNextValue(); }  int getNextRandomValue(void) {     return rand(); }  int main(void) {     int myarray[10];     populate_array(myarray, 10, getNextRandomValue);     ... } 

Here, the populate_array function takes a function pointer as its third parameter, and calls it to get the values to populate the array with. We’ve written the callback getNextRandomValue, which returns a random-ish value, and passed a pointer to it to populate_array. populate_array will call our callback function 10 times and assign the returned values to the elements in the given array.