memcpy(), what should the value of the size parameter be?

Question

I want to copy an int array to another int array. They use the same define for length so they\'ll always be of the same length.

What are the pros/cons of the followi

Answer 1

sizeof(X) always gives you the NUMBER OF BYTES of "X" if X is a uint16_t array of 10, then sizeof(X) will return 20

uint16_t X[10]={0};
cout<<"sizeof x: "< sizeof x: 20

if you want the number of elements you have to do a bit of byte arithmetic:
8bit = 1byte
16bit = 2bytes
32bit = 4 bytes
64bit = 8 bytes

so to get the number of elements you could do:

 numb_of_elements = ( sizeof(X)/sizeof(X[0]) );

resulting in:

uint32_t source[100]={0};
memcpy((void*) dest, (void*) source, ( sizeof(source)/sizeof(source[0]) ));

of course you would probably want to make ( sizeof(X)/sizeof(X[0]) ) a constant/variable so that you don't compute each time.. ( I don't know if compilers will always optimize this)