How do I count the number of zero bits in an integer?

Question

How would i go about finding the number of \'zero\' bits in C++. Suppose I have an integer;

int value = 276; 

For which I have the bits 100010

Answer 1

Do a one's compliment then count the 1s.

count_zero_bits( x ) = count_one_bits( ~x );

Implement the code to count the ones.

template< typename I > 
int count_one_bits( I i )
{
   size_t numbits = 0;
   for( ; i != 0; i >>= 1 )
   {
      numbits += i&1;
   }
}

although there is an issue with my function if i is a negative number because >> will put 1 bits into the right hand side so you will get a never-terminating loop. If there is a templated way to enforce an unsigned type that would be ideal.

Once you have that then:

template< typename I > int count_zero_bits( I i )
{
   return count_one_bits( ~i );
}

will work.