Can I turn unsigned char into char and vice versa?

Question

I want to use a function that expects data like this:

void process(char *data_in, int data_len);

So it\'s just processing some bytes really

Answer 1

unsigned char or signed char is just interpretation: there is no conversion happening.

Since you are processing bytes, to show intent, it would be better to declare as

void process(unsigned char *data_in, int data_len);

[As noted by an editor: A plain char may be either a signed or an unsigned type. The C and C++ standards explicitly allow either (it is always a separate type from either unsigned char or signed char, but has the same range as one of them)]