What are the differences between using array offsets vs pointer incrementation?

Question

Given 2 functions, which should be faster, if there is any difference at all? Assume that the input data is very large

void iterate1(const char* pIn, int Size)
{         


        

Answer 1

They are almost identical. Both solutions involve a temporary variable, an increment of a word on your system (int or ptr), and a logical check which should take one assembly instruction.

The only difference I see is the array lookup

arr[idx]

might require pointer arithmetic then a fetch while the dereference:

*ptr

just requires a fetch

My advice is that if it really matters, implement both and see if there's any savings.