bitmap

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

unsigned char *bitmapinit(int n);
unsigned char chkbit(unsigned char *map, int n);
void setbit(unsigned char *map, int n);
void unsetbit(unsigned char *map, int n);

unsigned char mask[8] = {1,2,4,8,16,32,64,128};

int main(int argc, char *argv[])
{
    int i;
    unsigned char *bitmap = bitmapinit(1000);
    if (!bitmap) {
        perror("malloc: ");
        exit(EXIT_FAILURE);
    }
    for (i = 0; i < 50; i++) {
        setbit(bitmap, i);
    }
    for (i = 0; i < 50; i += 5) {
        unsetbit(bitmap, i);
    }
    for (i = 0; i < 50; i++) {
        printf("bit #%d = %d\n", i, (chkbit(bitmap, i))?1:0);
    }
    return 0;
}

unsigned char *bitmapinit(int n)
{
    return (unsigned char *)calloc(sizeof(unsigned char), n / 8 + 1);
}
unsigned char chkbit(unsigned char *map, int n)
{
    return (unsigned char)map[n / 8] & mask[n % 8];
}
void setbit(unsigned char *map, int n)
{
    map[n / 8] = map[n / 8] | mask[n % 8];
}
void unsetbit(unsigned char *map, int n)
{
    map[n / 8] = map[n / 8] & ~(mask[n % 8]);
}