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

Of course the obvious source of bit-twiddling hacks is here: http://graphics.stanford.edu/~seander/bithacks.html#BitReverseObvious