#include <sys/stat.h>


struct Task
{
    unsigned uid;
    int gid_count;
    unsigned *gids;
};


static _Bool find_gid(unsigned gid, const unsigned *gids, int gid_count)
{
    for (int i = 0; i < gid_count; i++) {
        if (gid == gids[i]) {
            return 1;
        }
    }
    return 0;
}


static _Bool check_mode(int access, int mode)
{
    enum { OK = 0b111 };
    return ((~access | mode) & OK) == OK;
}


int myaccess(const struct stat *stb, const struct Task *task, int access)
{
    enum {
        MASK = 0b111,
        U_SHIFT = 6,
        G_SHIFT = 3
    };
    if (!task->uid || (stb->st_uid == task->uid && check_mode(access, stb->st_mode >> U_SHIFT))) {
        return 1;
    }
    if (find_gid(stb->st_gid, task->gids, task->gid_count) &&
        check_mode(access, (stb->st_mode >> G_SHIFT) & MASK)) {
        return 1;
    }
    if (check_mode(access, stb->st_mode & MASK)) {
        return 1;
    }
    return 0;
}