Bitmap - School HW

bitmap.c

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#define BITS_IN_INT sizeof(int) * CHAR_BIT
#define BITMAP_SIZE (UCHAR_MAX + 1) / BITS_IN_INT

void set(int bitmap[], int bit, int val)
{
    int mask = 1 << bit % BITS_IN_INT;
    int *b = bitmap + bit / BITS_IN_INT;

    if (val)
        *b |= mask; 
    else
        *b &= ~mask;
}

int get(int bitmap[], int bit)
{
    int mask = 1 << bit % BITS_IN_INT;
    int *b = bitmap + bit / BITS_IN_INT;
    return !!(*b & mask);                   // make sure to return 0 | 1
}

int count_ones(int num)
{
    int ones = 0;
    for (; num; ones++)
        num = num & (num - 1);
    return ones;
}

int count(int bitmap[], int size)
{
    int ones = 0;
    for (int i = 0; i < size; ++i) {
        ones += count_ones(bitmap[i]);
    }
    return ones;
}

int main()
{
    int bitmap[BITMAP_SIZE] = { 0 };
    
    set(bitmap, 'a', 1);
    printf("a: %d\n", get(bitmap, 'a'));
    printf("b: %d\n", get(bitmap, 'b'));
    printf("1's: %d\n", count(bitmap, BITMAP_SIZE));

    return 0;
}