Exersize - Programming Fundamental

Program to get pop count

int pop(unsigned x)
{
    x = x - ((x >> 1) & 0x55555555);
    x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
    x = (x + (x >> 4)) & 0x0F0F0F0F;
    x = x + (x >> 8);
    x = x + (x >> 16);
    return x & 0x0000003F;
}

another methood

int pop2(unsigned i)
{
     i = i - ((i >> 1) & 0x55555555);        // add pairs of bits
     i = (i & 0x33333333) + ((i >> 2) & 0x33333333);  // quads
     i = (i + (i >> 4)) & 0x0F0F0F0F;        // groups of 8
     i *= 0x01010101;                        // horizontal sum of bytes
     return  i >> 24;
}

Reverse bit

unsigned char bytereverse(unsigned char b) {
  b = (b & 0x55) << 1 | (b & 0xAA) >> 1; // swap adjacent bits
  b = (b & 0x33) << 2 | (b & 0xCC) >> 2; // swap adjacent pairs
  b = (b & 0x0F) << 4 | (b & 0xF0) >> 4; // swap nibbles
  return b;
}

another methood

unsigned char bytereverse2(unsigned char b) {
  return ((b << 1) | (b >> 7));
}