convert unsigned integer to byte array in C

Question

Can you explain about how to convert the last 3 bytes of data from unsigned integer to a character array?

Example:

unsigned int unint = some value;
unsigned char array[3];

Solution 1

It's more difficult if you have to convert it to an array, but if you just want to access the individual bytes, then you can do

char* bytes = (char*)&unint;

If you really do want to make an array (and therefore make a copy of the last 3 bytes, not leave them in place) you do

unsigned char bytes[3]; // or char, but unsigned char is better

bytes[0] = unint >> 16 & 0xFF;
bytes[1] = unint >> 8  & 0xFF;
bytes[2] = unint       & 0xFF;

Solution 2

You can do using it the bitwise right shift operator:

array[0] = unint;
array[1] = unint >> 8;
array[2] = unint >> 16;

The least signifcant byte of uint is stored in the first element of the array.