Char substraction with clipped underflow

Question

is there a way to compute:

/** clipped(a - b) **/
unsigned char clipped_substract(unsigned char a, unsigned char b)
{
    return a > b ? a - b : 0;
}

using some binary operations instead of a test?

Answer 1

/** clipped(a - b) **/
unsigned char clipped_substract(unsigned char a, unsigned char b)
{
    return a - (a+b) / 2 + getAbs(a-b) / 2;
}

unsigned int getAbs(int n)
{
    int const mask = n >> (sizeof(int) * 8 - 1);

    return ((n + mask) ^ mask);
}