Question

I am trying to convert an int into three bytes representing that int (big endian).

I’m sure it has something to do with bit-wise and and bit shifting. But I have no idea how to go about doing it.

For example:

int myInt;  // some code  byte b1, b2 , b3; // b1 is most significant, then b2 then b3. 

*Note, I am aware that an int is 4 bytes and the three bytes have a chance of over/underflowing.

Answer 1

To get the least significant byte:

b3 = myInt & 0xFF; 

The 2nd least significant byte:

b2 = (myInt >> 8) & 0xFF; 

And the 3rd least significant byte:

b1 = (myInt >> 16) & 0xFF; 

Explanation:

Bitwise ANDing a value with 0xFF (11111111 in binary) will return the least significant 8 bits (bits 0 to 7) in that number. Shifting the number to the right 8 times puts bits 8 to 15 into bit positions 0 to 7 so ANDing with 0xFF will return the second byte. Similarly, shifting the number to the right 16 times puts bits 16 to 23 into bit positions 0 to 7 so ANDing with 0xFF returns the 3rd byte.