generics

We don’t want to write the same thing many times; generics minimizes code duplication. Therefore, generics!

Let’s implement a simple swap function:

void swap_ptr_values(void *data1ptr, void *data2ptr, size_t datasize) {
}

helper functions

memcpy

Copy datasize bytes worth of memory in the second argument into the first argument. The two arguments CANNOT OVERLAP otherwise, you risk UB.

void *memcpy(void *dest, void *src, size_t nbytes)

memmove

Its memcpy, but it works with overlapping data, and is slower.

void *memove(void *dest, void *src, size_t nbytes)

pointer arithmetic with generics

Unfortunately, given that we don’t know how big a void * pointer is, we can’t do pointer arithmetic against it because it still doesn’t know how big the pointer is. You can’t just add/subtract numbers to char *.

So, we actually have to do pointer arithmetic by casting the pointer to a char* which will make pointer arithmetic work at the one-byte level.

void *return_sixth_elem(void *arr) {
    return (char *)arr + 5;
}

higher order functions

We can pass a function as a parameter.

bool (*function_name)(int, int)