#include <ftw.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <limits.h>
#include <pthread.h>

struct history
{
        struct history *chain;
        dev_t dev;
        ino_t ino;
        int level;
        int base;
};

#undef dirfd
#define dirfd(d) (*(int *)d)

static int do_nftw(char *path, int (*fn)(const char *, const struct stat *, int, struct FTW *), int fd_limit, int flags, struct history *h)
{
        size_t l = strlen(path), j = l && path[l-1]=='/' ? l-1 : l;
        struct stat st;
        struct history new;
        int type;
        int r;
        int dfd;
        int err;
        struct FTW lev;

        if ((flags & FTW_PHYS) ? lstat(path, &st) : stat(path, &st) < 0) {
                if (!(flags & FTW_PHYS) && errno==ENOENT && !lstat(path, &st))
                        type = FTW_SLN;
                else if (errno != EACCES) return -1;
                else type = FTW_NS;
        } else if (S_ISDIR(st.st_mode)) {
                if (flags & FTW_DEPTH) type = FTW_DP;
                else type = FTW_D;
        } else if (S_ISLNK(st.st_mode)) {
                if (flags & FTW_PHYS) type = FTW_SL;
                else type = FTW_SLN;
        } else {
                type = FTW_F;
        }

        if ((flags & FTW_MOUNT) && h && st.st_dev != h->dev)
                return 0;

        new.chain = h;
        new.dev = st.st_dev;
        new.ino = st.st_ino;
        new.level = h ? h->level+1 : 0;
        new.base = j+1;

        lev.level = new.level;
        if (h) {
                lev.base = h->base;
        } else {
                size_t k;
                for (k=j; k && path[k]=='/'; k--);
                for (; k && path[k-1]!='/'; k--);
                lev.base = k;
        }

        if (type == FTW_D || type == FTW_DP) {
                dfd = open(path, O_RDONLY);
                err = errno;
                if (dfd < 0 && err == EACCES) type = FTW_DNR;
                if (!fd_limit) close(dfd);
        }

        if (!(flags & FTW_DEPTH) && (r=fn(path, &st, type, &lev)))
                return r;

        for (; h; h = h->chain)
                if (h->dev == st.st_dev && h->ino == st.st_ino)
                        return 0;

        if ((type == FTW_D || type == FTW_DP) && fd_limit) {
                if (dfd < 0) {
                        errno = err;
                        return -1;
                }
                {
                DIR *d = fdopendir(dfd);
                if (d) {
                        struct dirent *de;
                        while ((de = readdir(d))) {
                                if (de->d_name[0] == '.'
                                 && (!de->d_name[1]
                                  || (de->d_name[1]=='.'
                                   && !de->d_name[2]))) continue;
                                if (strlen(de->d_name) >= PATH_MAX-l) {
                                        errno = ENAMETOOLONG;
                                        closedir(d);
                                        return -1;
                                }
                                path[j]='/';
                                strcpy(path+j+1, de->d_name);
                                if ((r=do_nftw(path, fn, fd_limit-1, flags, &new))) {
                                        closedir(d);
                                        return r;
                                }
                        }
                        closedir(d);
                } else {
                        close(dfd);
                        return -1;
                }
                }
        }

        path[l] = 0;
        if ((flags & FTW_DEPTH) && (r=fn(path, &st, type, &lev)))
                return r;

        return 0;
}

int nftw(const char *path, int (*fn)(const char *, const struct stat *, int, struct FTW *), int fd_limit, int flags)
{
        int r, cs;
        size_t l;
        char pathbuf[PATH_MAX+1];

        if (fd_limit <= 0) return 0;

        l = strlen(path);
        if (l > PATH_MAX) {
                errno = ENAMETOOLONG;
                return -1;
        }
        memcpy(pathbuf, path, l+1);

        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
        r = do_nftw(pathbuf, fn, fd_limit, flags, NULL);
        pthread_setcancelstate(cs, 0);
        return r;
}