In C/C++ what's the simplest way to reverse the order of bits in a byte?

Question

While there are multiple ways to reverse bit order in a byte, I'm curious as to what is the "simplest" for a developer to implement. And by reversing I mean:

1110 -> 0111
0010 -> 0100

This is similar to, but not a duplicate of this PHP question.

This is similar to, but not a duplicate of this C question. This question is asking for the easiest method to implement by a developer. The "Best Algorithm" is concerned with memory and cpu performance.

Answer 1

This should work:

unsigned char reverse(unsigned char b) {
   b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
   b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
   b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
   return b;
}

First the left four bits are swapped with the right four bits. Then all adjacent pairs are swapped and then all adjacent single bits. This results in a reversed order.