Boolean配列

boolean_array.c

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

static void set_bit(unsigned char* barray,  int idx)
{
    div_t t;
    t = div(idx, 8);
    *(barray + t.quot) |= (1 << t.rem);
}
static int ref_bit(unsigned char* barray,  int idx)
{
    div_t t;
    t = div(idx, 8);
    return (*(barray + t.quot) & (1 << t.rem)) > 0;
}
static void clear_bit(unsigned char* barray,  int idx)
{
    div_t t;
    t = div(idx, 8);
    *(barray + t.quot) &= (unsigned char)(~(1 << t.rem));
}

int main(void)
{
    unsigned char array[8] = {0};
    int i;

    set_bit(array, 5);
    assert(array[0] == 0x20);
    set_bit(array, 13);
    assert(array[1] == 0x20);
    assert(ref_bit(array, 5) == 1);
    assert(ref_bit(array, 13) == 1);
    clear_bit(array, 13);
    assert(ref_bit(array, 13) == 0);

    return 0;
}