Efficient Algorithm for Bit Reversal (from MSB->LSB to LSB->MSB) in C

Question

What is the most efficient algorithm to achieve the following:

0010 0000 => 0000 0100

The conversion is from MSB->LSB to LSB->MSB. All bits

Answer 1

I think the simplest method I know follows. MSB is input and LSB is 'reversed' output:

unsigned char rev(char MSB) {
    unsigned char LSB=0;  // for output
    _FOR(i,0,8) {
        LSB= LSB << 1;
        if(MSB&1) LSB = LSB | 1;
        MSB= MSB >> 1;
    }
    return LSB;
}

//    It works by rotating bytes in opposite directions. 
//    Just repeat for each byte.