/**
 * :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)
{
    printf("get_bit_count(%d)\n", x);

    int i;
    int x_and_mask;
    int x_shifted;
    int x_shifted_and_mask;
    int shift; /* Number of positions to shift to right*/
    for (i = 0, shift = 1; i < 5; i++, shift *= 2) {
        printf("    START loop\n");
        printf("        i = %d, x = %d, shift = %d\n", i, x, shift);

        x_and_mask = x & mask[i];
        printf("        x & mask[i] = %d\n", x_and_mask);

        x_shifted = x >> shift;
        printf("        x >> shift = %d\n", x_shifted);

        x_shifted_and_mask = x_shifted & mask[i];
        printf("        (x >> shift) & mask[i] = %d\n", x_shifted_and_mask);

        x = x_and_mask + x_shifted_and_mask;
        printf("        x = %d\n", x);
        printf("    END loop\n");
    }

    return x;
}


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

    /*
    size_t mask_len = sizeof(mask) / sizeof(unsigned int);

    for (int i = 0; i < mask_len; i++) {
        printf("mask[%d] = %d\n", i, mask[i]);
    }
    */

    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
 */