/**
 * :author: Dan Buch (daniel.buch@gmail.com)
 */

#include <stdio.h>

static unsigned int mask[] = {
    0x55555555,
    0x33333333,
    0x0F0F0F0F,
    0x00FF00FF,
    0x0000FFFF
};


int get_bit_count(unsigned int x)
{

    int i;
    int shift; /* Number of positions to shift to right*/
    for (i = 0, shift = 1; i < 5; i++, shift *= 2) {
        x = (x & mask[i]) + ((x >> shift) & mask[i]);
    }
    return x;
}


int main()
{
    int to_test[] = {0, 5, 7};
    int current;

    for (int i = 0; i < 3 ; i++) {
        current = to_test[i];
        printf("get_bit_count(%d) = %d\n", current, get_bit_count(current));
    }
}

/* vim:filetype=c:fileencoding=utf-8
 */