(fts_cross_check) [FTS_DEBUG]: s/active_dir_ht/fts_cycle.ht/.

[pspp] / lib / fts.c

/* Traverse a file hierarchy.

   Copyright (C) 2004, 2005 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/*-
 * Copyright (c) 1990, 1993, 1994
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fts.c       8.6 (Berkeley) 8/14/94";
#endif /* LIBC_SCCS and not lint */

#include "fts_.h"

#if HAVE_SYS_PARAM_H || defined _LIBC
# include <sys/param.h>
#endif
#ifdef _LIBC
# include <include/sys/stat.h>
#else
# include <sys/stat.h>
#endif
#include <fcntl.h>
#include <errno.h>
#include "dirfd.h"
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#if ! _LIBC
# include "lstat.h"
#endif

#if defined _LIBC
# include <dirent.h>
# define NAMLEN(dirent) _D_EXACT_NAMLEN (dirent)
#else
# if HAVE_DIRENT_H
#  include <dirent.h>
#  define NAMLEN(dirent) strlen ((dirent)->d_name)
# else
#  define dirent direct
#  define NAMLEN(dirent) (dirent)->d_namlen
#  if HAVE_SYS_NDIR_H
#   include <sys/ndir.h>
#  endif
#  if HAVE_SYS_DIR_H
#   include <sys/dir.h>
#  endif
#  if HAVE_NDIR_H
#   include <ndir.h>
#  endif
# endif
#endif

#ifdef _LIBC
# undef close
# define close __close
# undef closedir
# define closedir __closedir
# undef fchdir
# define fchdir __fchdir
# undef open
# define open __open
# undef opendir
# define opendir __opendir
# undef readdir
# define readdir __readdir
#else
# undef internal_function
# define internal_function /* empty */
#endif

#ifndef __set_errno
# define __set_errno(Val) errno = (Val)
#endif

#ifndef __attribute__
# if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8) || __STRICT_ANSI__
#  define __attribute__(x) /* empty */
# endif
#endif

#ifndef ATTRIBUTE_UNUSED
# define ATTRIBUTE_UNUSED __attribute__ ((__unused__))
#endif


static FTSENT   *fts_alloc (FTS *, const char *, size_t) internal_function;
static FTSENT   *fts_build (FTS *, int) internal_function;
static void      fts_lfree (FTSENT *) internal_function;
static void      fts_load (FTS *, FTSENT *) internal_function;
static size_t    fts_maxarglen (char * const *) internal_function;
static void      fts_padjust (FTS *, FTSENT *) internal_function;
static bool      fts_palloc (FTS *, size_t) internal_function;
static FTSENT   *fts_sort (FTS *, FTSENT *, size_t) internal_function;
static unsigned short int fts_stat (FTS *, FTSENT *, bool) internal_function;
static int      fts_safe_changedir (FTS *, FTSENT *, int, const char *)
     internal_function;

#if _LGPL_PACKAGE
static bool enter_dir (FTS *fts, FTSENT *ent) { return true; }
static void leave_dir (FTS *fts, FTSENT *ent) {}
static bool setup_dir (FTS *fts) { return true; }
static void free_dir (FTS *fts) {}
#else
# include "fcntl--.h"
# include "fts-cycle.c"
#endif

#ifndef MAX
# define MAX(a,b) ((a) > (b) ? (a) : (b))
#endif

#ifndef SIZE_MAX
# define SIZE_MAX ((size_t) -1)
#endif

#ifndef O_DIRECTORY
# define O_DIRECTORY 0
#endif

#define ISDOT(a)        (a[0] == '.' && (!a[1] || (a[1] == '.' && !a[2])))

#define CLR(opt)        (sp->fts_options &= ~(opt))
#define ISSET(opt)      (sp->fts_options & (opt))
#define SET(opt)        (sp->fts_options |= (opt))

#define FCHDIR(sp, fd)  (!ISSET(FTS_NOCHDIR) && fchdir(fd))

/* fts_build flags */
#define BCHILD          1               /* fts_children */
#define BNAMES          2               /* fts_children, names only */
#define BREAD           3               /* fts_read */

#if FTS_DEBUG
# include <inttypes.h>
# include <stdint.h>
# include <stdio.h>
bool fts_debug = false;
# define Dprintf(x) do { if (fts_debug) printf x; } while (0)
#else
# define Dprintf(x)
#endif

#define LEAVE_DIR(Fts, Ent, Tag)                                \
  do                                                            \
    {                                                           \
      Dprintf (("  %s-leaving: %s\n", Tag, (Ent)->fts_path));   \
      leave_dir (Fts, Ent);                                     \
    }                                                           \
  while (false)

/* Open the directory DIR if possible, and return a file
   descriptor.  Return -1 and set errno on failure.  It doesn't matter
   whether the file descriptor has read or write access.  */

static int
internal_function
diropen (char const *dir)
{
  int fd = open (dir, O_RDONLY | O_DIRECTORY);
  if (fd < 0)
    fd = open (dir, O_WRONLY | O_DIRECTORY);
  return fd;
}

FTS *
fts_open (char * const *argv,
          register int options,
          int (*compar) (FTSENT const **, FTSENT const **))
{
        register FTS *sp;
        register FTSENT *p, *root;
        register size_t nitems;
        FTSENT *parent, *tmp = NULL;    /* pacify gcc */
        size_t len;

        /* Options check. */
        if (options & ~FTS_OPTIONMASK) {
                __set_errno (EINVAL);
                return (NULL);
        }

        /* Allocate/initialize the stream */
        if ((sp = malloc(sizeof(FTS))) == NULL)
                return (NULL);
        memset(sp, 0, sizeof(FTS));
        sp->fts_compar = compar;
        sp->fts_options = options;

        /* Logical walks turn on NOCHDIR; symbolic links are too hard. */
        if (ISSET(FTS_LOGICAL))
                SET(FTS_NOCHDIR);

        /*
         * Start out with 1K of file name space, and enough, in any case,
         * to hold the user's file names.
         */
#ifndef MAXPATHLEN
# define MAXPATHLEN 1024
#endif
        if (! fts_palloc(sp, MAX(fts_maxarglen(argv), MAXPATHLEN)))
                goto mem1;

        /* Allocate/initialize root's parent. */
        if ((parent = fts_alloc(sp, "", 0)) == NULL)
                goto mem2;
        parent->fts_level = FTS_ROOTPARENTLEVEL;

        /* Allocate/initialize root(s). */
        for (root = NULL, nitems = 0; *argv != NULL; ++argv, ++nitems) {
                /* Don't allow zero-length file names. */
                if ((len = strlen(*argv)) == 0) {
                        __set_errno (ENOENT);
                        goto mem3;
                }

                if ((p = fts_alloc(sp, *argv, len)) == NULL)
                        goto mem3;
                p->fts_level = FTS_ROOTLEVEL;
                p->fts_parent = parent;
                p->fts_accpath = p->fts_name;
                p->fts_info = fts_stat(sp, p, ISSET(FTS_COMFOLLOW) != 0);

                /* Command-line "." and ".." are real directories. */
                if (p->fts_info == FTS_DOT)
                        p->fts_info = FTS_D;

                /*
                 * If comparison routine supplied, traverse in sorted
                 * order; otherwise traverse in the order specified.
                 */
                if (compar) {
                        p->fts_link = root;
                        root = p;
                } else {
                        p->fts_link = NULL;
                        if (root == NULL)
                                tmp = root = p;
                        else {
                                tmp->fts_link = p;
                                tmp = p;
                        }
                }
        }
        if (compar && nitems > 1)
                root = fts_sort(sp, root, nitems);

        /*
         * Allocate a dummy pointer and make fts_read think that we've just
         * finished the node before the root(s); set p->fts_info to FTS_INIT
         * so that everything about the "current" node is ignored.
         */
        if ((sp->fts_cur = fts_alloc(sp, "", 0)) == NULL)
                goto mem3;
        sp->fts_cur->fts_link = root;
        sp->fts_cur->fts_info = FTS_INIT;
        if (! setup_dir (sp))
          goto mem3;

        /*
         * If using chdir(2), grab a file descriptor pointing to dot to ensure
         * that we can get back here; this could be avoided for some file names,
         * but almost certainly not worth the effort.  Slashes, symbolic links,
         * and ".." are all fairly nasty problems.  Note, if we can't get the
         * descriptor we run anyway, just more slowly.
         */
        if (!ISSET(FTS_NOCHDIR)
            && (sp->fts_rfd = diropen (".")) < 0)
                SET(FTS_NOCHDIR);

        return (sp);

mem3:   fts_lfree(root);
        free(parent);
mem2:   free(sp->fts_path);
mem1:   free(sp);
        return (NULL);
}

static void
internal_function
fts_load (FTS *sp, register FTSENT *p)
{
        register size_t len;
        register char *cp;

        /*
         * Load the stream structure for the next traversal.  Since we don't
         * actually enter the directory until after the preorder visit, set
         * the fts_accpath field specially so the chdir gets done to the right
         * place and the user can access the first node.  From fts_open it's
         * known that the file name will fit.
         */
        len = p->fts_pathlen = p->fts_namelen;
        memmove(sp->fts_path, p->fts_name, len + 1);
        if ((cp = strrchr(p->fts_name, '/')) && (cp != p->fts_name || cp[1])) {
                len = strlen(++cp);
                memmove(p->fts_name, cp, len + 1);
                p->fts_namelen = len;
        }
        p->fts_accpath = p->fts_path = sp->fts_path;
        sp->fts_dev = p->fts_statp->st_dev;
}

int
fts_close (FTS *sp)
{
        register FTSENT *freep, *p;
        int saved_errno = 0;

        /*
         * This still works if we haven't read anything -- the dummy structure
         * points to the root list, so we step through to the end of the root
         * list which has a valid parent pointer.
         */
        if (sp->fts_cur) {
                for (p = sp->fts_cur; p->fts_level >= FTS_ROOTLEVEL;) {
                        freep = p;
                        p = p->fts_link != NULL ? p->fts_link : p->fts_parent;
                        free(freep);
                }
                free(p);
        }

        /* Free up child linked list, sort array, file name buffer. */
        if (sp->fts_child)
                fts_lfree(sp->fts_child);
        if (sp->fts_array)
                free(sp->fts_array);
        free(sp->fts_path);

        /* Return to original directory, save errno if necessary. */
        if (!ISSET(FTS_NOCHDIR)) {
                if (fchdir(sp->fts_rfd))
                        saved_errno = errno;
                (void)close(sp->fts_rfd);
        }

        free_dir (sp);

        /* Free up the stream pointer. */
        free(sp);

        /* Set errno and return. */
        if (saved_errno) {
                __set_errno (saved_errno);
                return (-1);
        }

        return (0);
}

/*
 * Special case of "/" at the end of the file name so that slashes aren't
 * appended which would cause file names to be written as "....//foo".
 */
#define NAPPEND(p)                                                      \
        (p->fts_path[p->fts_pathlen - 1] == '/'                         \
            ? p->fts_pathlen - 1 : p->fts_pathlen)

FTSENT *
fts_read (register FTS *sp)
{
        register FTSENT *p, *tmp;
        register unsigned short int instr;
        register char *t;
        int saved_errno;

        /* If finished or unrecoverable error, return NULL. */
        if (sp->fts_cur == NULL || ISSET(FTS_STOP))
                return (NULL);

        /* Set current node pointer. */
        p = sp->fts_cur;

        /* Save and zero out user instructions. */
        instr = p->fts_instr;
        p->fts_instr = FTS_NOINSTR;

        /* Any type of file may be re-visited; re-stat and re-turn. */
        if (instr == FTS_AGAIN) {
                p->fts_info = fts_stat(sp, p, false);
                return (p);
        }
        Dprintf (("fts_read: p=%s\n",
                  p->fts_info == FTS_INIT ? "" : p->fts_path));

        /*
         * Following a symlink -- SLNONE test allows application to see
         * SLNONE and recover.  If indirecting through a symlink, have
         * keep a pointer to current location.  If unable to get that
         * pointer, follow fails.
         */
        if (instr == FTS_FOLLOW &&
            (p->fts_info == FTS_SL || p->fts_info == FTS_SLNONE)) {
                p->fts_info = fts_stat(sp, p, true);
                if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
                        if ((p->fts_symfd = diropen (".")) < 0) {
                                p->fts_errno = errno;
                                p->fts_info = FTS_ERR;
                        } else
                                p->fts_flags |= FTS_SYMFOLLOW;
                }
                goto check_for_dir;
        }

        /* Directory in pre-order. */
        if (p->fts_info == FTS_D) {
                /* If skipped or crossed mount point, do post-order visit. */
                if (instr == FTS_SKIP ||
                    (ISSET(FTS_XDEV) && p->fts_statp->st_dev != sp->fts_dev)) {
                        if (p->fts_flags & FTS_SYMFOLLOW)
                                (void)close(p->fts_symfd);
                        if (sp->fts_child) {
                                fts_lfree(sp->fts_child);
                                sp->fts_child = NULL;
                        }
                        p->fts_info = FTS_DP;
                        LEAVE_DIR (sp, p, "1");
                        return (p);
                }

                /* Rebuild if only read the names and now traversing. */
                if (sp->fts_child != NULL && ISSET(FTS_NAMEONLY)) {
                        CLR(FTS_NAMEONLY);
                        fts_lfree(sp->fts_child);
                        sp->fts_child = NULL;
                }

                /*
                 * Cd to the subdirectory.
                 *
                 * If have already read and now fail to chdir, whack the list
                 * to make the names come out right, and set the parent errno
                 * so the application will eventually get an error condition.
                 * Set the FTS_DONTCHDIR flag so that when we logically change
                 * directories back to the parent we don't do a chdir.
                 *
                 * If haven't read do so.  If the read fails, fts_build sets
                 * FTS_STOP or the fts_info field of the node.
                 */
                if (sp->fts_child != NULL) {
                        if (fts_safe_changedir(sp, p, -1, p->fts_accpath)) {
                                p->fts_errno = errno;
                                p->fts_flags |= FTS_DONTCHDIR;
                                for (p = sp->fts_child; p != NULL;
                                     p = p->fts_link)
                                        p->fts_accpath =
                                            p->fts_parent->fts_accpath;
                        }
                } else if ((sp->fts_child = fts_build(sp, BREAD)) == NULL) {
                        if (ISSET(FTS_STOP))
                                return (NULL);
                        /* If fts_build's call to fts_safe_changedir failed
                           because it was not able to fchdir into a
                           subdirectory, tell the caller.  */
                        if (p->fts_errno)
                                p->fts_info = FTS_ERR;
                        /* FIXME: see if this should be in an else block */
                        LEAVE_DIR (sp, p, "2");
                        return (p);
                }
                p = sp->fts_child;
                sp->fts_child = NULL;
                goto name;
        }

        /* Move to the next node on this level. */
next:   tmp = p;
        if ((p = p->fts_link) != NULL) {
                free(tmp);

                /*
                 * If reached the top, return to the original directory (or
                 * the root of the tree), and load the file names for the next
                 * root.
                 */
                if (p->fts_level == FTS_ROOTLEVEL) {
                        if (FCHDIR(sp, sp->fts_rfd)) {
                                SET(FTS_STOP);
                                return (NULL);
                        }
                        fts_load(sp, p);
                        goto check_for_dir;
                }

                /*
                 * User may have called fts_set on the node.  If skipped,
                 * ignore.  If followed, get a file descriptor so we can
                 * get back if necessary.
                 */
                if (p->fts_instr == FTS_SKIP)
                        goto next;
                if (p->fts_instr == FTS_FOLLOW) {
                        p->fts_info = fts_stat(sp, p, true);
                        if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
                                if ((p->fts_symfd = diropen (".")) < 0) {
                                        p->fts_errno = errno;
                                        p->fts_info = FTS_ERR;
                                } else
                                        p->fts_flags |= FTS_SYMFOLLOW;
                        }
                        p->fts_instr = FTS_NOINSTR;
                }

name:           t = sp->fts_path + NAPPEND(p->fts_parent);
                *t++ = '/';
                memmove(t, p->fts_name, p->fts_namelen + 1);
check_for_dir:
                sp->fts_cur = p;
                if (p->fts_info == FTS_D)
                  {
                    Dprintf (("  %s-entering: %s\n", sp, p->fts_path));
                    if (! enter_dir (sp, p))
                      {
                        __set_errno (ENOMEM);
                        return NULL;
                      }
                  }
                return p;
        }

        /* Move up to the parent node. */
        p = tmp->fts_parent;
        free(tmp);

        if (p->fts_level == FTS_ROOTPARENTLEVEL) {
                /*
                 * Done; free everything up and set errno to 0 so the user
                 * can distinguish between error and EOF.
                 */
                free(p);
                __set_errno (0);
                return (sp->fts_cur = NULL);
        }

        /* NUL terminate the file name.  */
        sp->fts_path[p->fts_pathlen] = '\0';

        /*
         * Return to the parent directory.  If at a root node or came through
         * a symlink, go back through the file descriptor.  Otherwise, cd up
         * one directory.
         */
        if (p->fts_level == FTS_ROOTLEVEL) {
                if (FCHDIR(sp, sp->fts_rfd)) {
                        p->fts_errno = errno;
                        SET(FTS_STOP);
                }
        } else if (p->fts_flags & FTS_SYMFOLLOW) {
                if (FCHDIR(sp, p->fts_symfd)) {
                        saved_errno = errno;
                        (void)close(p->fts_symfd);
                        __set_errno (saved_errno);
                        p->fts_errno = errno;
                        SET(FTS_STOP);
                }
                (void)close(p->fts_symfd);
        } else if (!(p->fts_flags & FTS_DONTCHDIR) &&
                   fts_safe_changedir(sp, p->fts_parent, -1, "..")) {
                p->fts_errno = errno;
                SET(FTS_STOP);
        }
        p->fts_info = p->fts_errno ? FTS_ERR : FTS_DP;
        if (p->fts_errno == 0)
                LEAVE_DIR (sp, p, "3");
        sp->fts_cur = p;
        return ISSET(FTS_STOP) ? NULL : p;
}

/*
 * Fts_set takes the stream as an argument although it's not used in this
 * implementation; it would be necessary if anyone wanted to add global
 * semantics to fts using fts_set.  An error return is allowed for similar
 * reasons.
 */
/* ARGSUSED */
int
fts_set(FTS *sp ATTRIBUTE_UNUSED, FTSENT *p, int instr)
{
        if (instr != 0 && instr != FTS_AGAIN && instr != FTS_FOLLOW &&
            instr != FTS_NOINSTR && instr != FTS_SKIP) {
                __set_errno (EINVAL);
                return (1);
        }
        p->fts_instr = instr;
        return (0);
}

FTSENT *
fts_children (register FTS *sp, int instr)
{
        register FTSENT *p;
        int fd;

        if (instr != 0 && instr != FTS_NAMEONLY) {
                __set_errno (EINVAL);
                return (NULL);
        }

        /* Set current node pointer. */
        p = sp->fts_cur;

        /*
         * Errno set to 0 so user can distinguish empty directory from
         * an error.
         */
        __set_errno (0);

        /* Fatal errors stop here. */
        if (ISSET(FTS_STOP))
                return (NULL);

        /* Return logical hierarchy of user's arguments. */
        if (p->fts_info == FTS_INIT)
                return (p->fts_link);

        /*
         * If not a directory being visited in pre-order, stop here.  Could
         * allow FTS_DNR, assuming the user has fixed the problem, but the
         * same effect is available with FTS_AGAIN.
         */
        if (p->fts_info != FTS_D /* && p->fts_info != FTS_DNR */)
                return (NULL);

        /* Free up any previous child list. */
        if (sp->fts_child != NULL)
                fts_lfree(sp->fts_child);

        if (instr == FTS_NAMEONLY) {
                SET(FTS_NAMEONLY);
                instr = BNAMES;
        } else
                instr = BCHILD;

        /*
         * If using chdir on a relative file name and called BEFORE fts_read
         * does its chdir to the root of a traversal, we can lose -- we need to
         * chdir into the subdirectory, and we don't know where the current
         * directory is, so we can't get back so that the upcoming chdir by
         * fts_read will work.
         */
        if (p->fts_level != FTS_ROOTLEVEL || p->fts_accpath[0] == '/' ||
            ISSET(FTS_NOCHDIR))
                return (sp->fts_child = fts_build(sp, instr));

        if ((fd = diropen (".")) < 0)
                return (sp->fts_child = NULL);
        sp->fts_child = fts_build(sp, instr);
        if (fchdir(fd)) {
                (void)close(fd);
                return (NULL);
        }
        (void)close(fd);
        return (sp->fts_child);
}

/*
 * This is the tricky part -- do not casually change *anything* in here.  The
 * idea is to build the linked list of entries that are used by fts_children
 * and fts_read.  There are lots of special cases.
 *
 * The real slowdown in walking the tree is the stat calls.  If FTS_NOSTAT is
 * set and it's a physical walk (so that symbolic links can't be directories),
 * we can do things quickly.  First, if it's a 4.4BSD file system, the type
 * of the file is in the directory entry.  Otherwise, we assume that the number
 * of subdirectories in a node is equal to the number of links to the parent.
 * The former skips all stat calls.  The latter skips stat calls in any leaf
 * directories and for any files after the subdirectories in the directory have
 * been found, cutting the stat calls by about 2/3.
 */
static FTSENT *
internal_function
fts_build (register FTS *sp, int type)
{
        register struct dirent *dp;
        register FTSENT *p, *head;
        register size_t nitems;
        FTSENT *cur, *tail;
        DIR *dirp;
        void *oldaddr;
        int cderrno;
        int saved_errno;
        bool descend;
        bool doadjust;
        ptrdiff_t level;
        nlink_t nlinks;
        bool nostat;
        size_t len, maxlen, new_len;
        char *cp;

        /* Set current node pointer. */
        cur = sp->fts_cur;

        /*
         * Open the directory for reading.  If this fails, we're done.
         * If being called from fts_read, set the fts_info field.
         */
#if defined FTS_WHITEOUT && 0
        if (ISSET(FTS_WHITEOUT))
                oflag = DTF_NODUP|DTF_REWIND;
        else
                oflag = DTF_HIDEW|DTF_NODUP|DTF_REWIND;
#else
# define __opendir2(file, flag) opendir(file)
#endif
       if ((dirp = __opendir2(cur->fts_accpath, oflag)) == NULL) {
                if (type == BREAD) {
                        cur->fts_info = FTS_DNR;
                        cur->fts_errno = errno;
                }
                return (NULL);
        }

        /*
         * Nlinks is the number of possible entries of type directory in the
         * directory if we're cheating on stat calls, 0 if we're not doing
         * any stat calls at all, (nlink_t) -1 if we're statting everything.
         */
        if (type == BNAMES) {
                nlinks = 0;
                /* Be quiet about nostat, GCC. */
                nostat = false;
        } else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
                nlinks = (cur->fts_statp->st_nlink
                          - (ISSET(FTS_SEEDOT) ? 0 : 2));
                nostat = true;
        } else {
                nlinks = -1;
                nostat = false;
        }

        /*
         * If we're going to need to stat anything or we want to descend
         * and stay in the directory, chdir.  If this fails we keep going,
         * but set a flag so we don't chdir after the post-order visit.
         * We won't be able to stat anything, but we can still return the
         * names themselves.  Note, that since fts_read won't be able to
         * chdir into the directory, it will have to return different file
         * names than before, i.e. "a/b" instead of "b".  Since the node
         * has already been visited in pre-order, have to wait until the
         * post-order visit to return the error.  There is a special case
         * here, if there was nothing to stat then it's not an error to
         * not be able to stat.  This is all fairly nasty.  If a program
         * needed sorted entries or stat information, they had better be
         * checking FTS_NS on the returned nodes.
         */
        cderrno = 0;
        if (nlinks || type == BREAD) {
                if (fts_safe_changedir(sp, cur, dirfd(dirp), NULL)) {
                        if (nlinks && type == BREAD)
                                cur->fts_errno = errno;
                        cur->fts_flags |= FTS_DONTCHDIR;
                        descend = false;
                        cderrno = errno;
                        closedir(dirp);
                        dirp = NULL;
                } else
                        descend = true;
        } else
                descend = false;

        /*
         * Figure out the max file name length that can be stored in the
         * current buffer -- the inner loop allocates more space as necessary.
         * We really wouldn't have to do the maxlen calculations here, we
         * could do them in fts_read before returning the name, but it's a
         * lot easier here since the length is part of the dirent structure.
         *
         * If not changing directories set a pointer so that can just append
         * each new component into the file name.
         */
        len = NAPPEND(cur);
        if (ISSET(FTS_NOCHDIR)) {
                cp = sp->fts_path + len;
                *cp++ = '/';
        } else {
                /* GCC, you're too verbose. */
                cp = NULL;
        }
        len++;
        maxlen = sp->fts_pathlen - len;

        level = cur->fts_level + 1;

        /* Read the directory, attaching each entry to the `link' pointer. */
        doadjust = false;
        for (head = tail = NULL, nitems = 0; dirp && (dp = readdir(dirp));) {
                if (!ISSET(FTS_SEEDOT) && ISDOT(dp->d_name))
                        continue;

                if ((p = fts_alloc(sp, dp->d_name, NAMLEN (dp))) == NULL)
                        goto mem1;
                if (NAMLEN (dp) >= maxlen) {/* include space for NUL */
                        oldaddr = sp->fts_path;
                        if (! fts_palloc(sp, NAMLEN (dp) + len + 1)) {
                                /*
                                 * No more memory.  Save
                                 * errno, free up the current structure and the
                                 * structures already allocated.
                                 */
mem1:                           saved_errno = errno;
                                if (p)
                                        free(p);
                                fts_lfree(head);
                                closedir(dirp);
                                cur->fts_info = FTS_ERR;
                                SET(FTS_STOP);
                                __set_errno (saved_errno);
                                return (NULL);
                        }
                        /* Did realloc() change the pointer? */
                        if (oldaddr != sp->fts_path) {
                                doadjust = true;
                                if (ISSET(FTS_NOCHDIR))
                                        cp = sp->fts_path + len;
                        }
                        maxlen = sp->fts_pathlen - len;
                }

                new_len = len + NAMLEN (dp);
                if (new_len < len) {
                        /*
                         * In the unlikely even that we would end up
                         * with a file name longer than SIZE_MAX, free up
                         * the current structure and the structures already
                         * allocated, then error out with ENAMETOOLONG.
                         */
                        free(p);
                        fts_lfree(head);
                        closedir(dirp);
                        cur->fts_info = FTS_ERR;
                        SET(FTS_STOP);
                        __set_errno (ENAMETOOLONG);
                        return (NULL);
                }
                p->fts_level = level;
                p->fts_parent = sp->fts_cur;
                p->fts_pathlen = new_len;

#if defined FTS_WHITEOUT && 0
                if (dp->d_type == DT_WHT)
                        p->fts_flags |= FTS_ISW;
#endif

                if (cderrno) {
                        if (nlinks) {
                                p->fts_info = FTS_NS;
                                p->fts_errno = cderrno;
                        } else
                                p->fts_info = FTS_NSOK;
                        p->fts_accpath = cur->fts_accpath;
                } else if (nlinks == 0
#if HAVE_STRUCT_DIRENT_D_TYPE
                           || (nostat &&
                               dp->d_type != DT_DIR && dp->d_type != DT_UNKNOWN)
#endif
                    ) {
                        p->fts_accpath =
                            ISSET(FTS_NOCHDIR) ? p->fts_path : p->fts_name;
                        p->fts_info = FTS_NSOK;
                } else {
                        /* Build a file name for fts_stat to stat. */
                        if (ISSET(FTS_NOCHDIR)) {
                                p->fts_accpath = p->fts_path;
                                memmove(cp, p->fts_name, p->fts_namelen + 1);
                        } else
                                p->fts_accpath = p->fts_name;
                        /* Stat it. */
                        p->fts_info = fts_stat(sp, p, false);

                        /* Decrement link count if applicable. */
                        if (nlinks > 0 && (p->fts_info == FTS_D ||
                            p->fts_info == FTS_DC || p->fts_info == FTS_DOT))
                                nlinks -= nostat;
                }

                /* We walk in directory order so "ls -f" doesn't get upset. */
                p->fts_link = NULL;
                if (head == NULL)
                        head = tail = p;
                else {
                        tail->fts_link = p;
                        tail = p;
                }
                ++nitems;
        }
        if (dirp)
                closedir(dirp);

        /*
         * If realloc() changed the address of the file name, adjust the
         * addresses for the rest of the tree and the dir list.
         */
        if (doadjust)
                fts_padjust(sp, head);

        /*
         * If not changing directories, reset the file name back to original
         * state.
         */
        if (ISSET(FTS_NOCHDIR)) {
                if (len == sp->fts_pathlen || nitems == 0)
                        --cp;
                *cp = '\0';
        }

        /*
         * If descended after called from fts_children or after called from
         * fts_read and nothing found, get back.  At the root level we use
         * the saved fd; if one of fts_open()'s arguments is a relative name
         * to an empty directory, we wind up here with no other way back.  If
         * can't get back, we're done.
         */
        if (descend && (type == BCHILD || !nitems) &&
            (cur->fts_level == FTS_ROOTLEVEL ?
             FCHDIR(sp, sp->fts_rfd) :
             fts_safe_changedir(sp, cur->fts_parent, -1, ".."))) {
                cur->fts_info = FTS_ERR;
                SET(FTS_STOP);
                return (NULL);
        }

        /* If didn't find anything, return NULL. */
        if (!nitems) {
                if (type == BREAD)
                        cur->fts_info = FTS_DP;
                return (NULL);
        }

        /* Sort the entries. */
        if (sp->fts_compar && nitems > 1)
                head = fts_sort(sp, head, nitems);
        return (head);
}

#if FTS_DEBUG

/* Walk ->fts_parent links starting at E_CURR, until the root of the
   current hierarchy.  There should be a directory with dev/inode
   matching those of AD.  If not, print a lot of diagnostics.  */
static void
find_matching_ancestor (FTSENT const *e_curr, struct Active_dir const *ad)
{
  FTSENT const *ent;
  for (ent = e_curr; ent->fts_level >= FTS_ROOTLEVEL; ent = ent->fts_parent)
    {
      if (ad->ino == ent->fts_statp->st_ino
          && ad->dev == ent->fts_statp->st_dev)
        return;
    }
  printf ("ERROR: tree dir, %s, not active\n", ad->fts_ent->fts_accpath);
  printf ("active dirs:\n");
  for (ent = e_curr;
       ent->fts_level >= FTS_ROOTLEVEL; ent = ent->fts_parent)
    printf ("  %s(%"PRIuMAX"/%"PRIuMAX") to %s(%"PRIuMAX"/%"PRIuMAX")...\n",
            ad->fts_ent->fts_accpath,
            (uintmax_t) ad->dev,
            (uintmax_t) ad->ino,
            ent->fts_accpath,
            (uintmax_t) ent->fts_statp->st_dev,
            (uintmax_t) ent->fts_statp->st_ino);
}

void
fts_cross_check (FTS const *sp)
{
  FTSENT const *ent = sp->fts_cur;
  FTSENT const *t;
  if ( ! ISSET (FTS_TIGHT_CYCLE_CHECK))
    return;

  Dprintf (("fts-cross-check cur=%s\n", ent->fts_path));
  /* Make sure every parent dir is in the tree.  */
  for (t = ent->fts_parent; t->fts_level >= FTS_ROOTLEVEL; t = t->fts_parent)
    {
      struct Active_dir ad;
      ad.ino = t->fts_statp->st_ino;
      ad.dev = t->fts_statp->st_dev;
      if ( ! hash_lookup (sp->fts_cycle.ht, &ad))
        printf ("ERROR: active dir, %s, not in tree\n", t->fts_path);
    }

  /* Make sure every dir in the tree is an active dir.
     But ENT is not necessarily a directory.  If so, just skip this part. */
  if (ent->fts_parent->fts_level >= FTS_ROOTLEVEL
      && (ent->fts_info == FTS_DP
          || ent->fts_info == FTS_D))
    {
      struct Active_dir *ad;
      for (ad = hash_get_first (sp->fts_cycle.ht); ad != NULL;
           ad = hash_get_next (sp->fts_cycle.ht, ad))
        {
          find_matching_ancestor (ent, ad);
        }
    }
}
#endif

static unsigned short int
internal_function
fts_stat(FTS *sp, register FTSENT *p, bool follow)
{
        struct stat *sbp = p->fts_statp;
        int saved_errno;

#if defined FTS_WHITEOUT && 0
        /* check for whiteout */
        if (p->fts_flags & FTS_ISW) {
                memset(sbp, '\0', sizeof (*sbp));
                sbp->st_mode = S_IFWHT;
                return (FTS_W);
       }
#endif

        /*
         * If doing a logical walk, or application requested FTS_FOLLOW, do
         * a stat(2).  If that fails, check for a non-existent symlink.  If
         * fail, set the errno from the stat call.
         */
        if (ISSET(FTS_LOGICAL) || follow) {
                if (stat(p->fts_accpath, sbp)) {
                        saved_errno = errno;
                        if (!lstat(p->fts_accpath, sbp)) {
                                __set_errno (0);
                                return (FTS_SLNONE);
                        }
                        p->fts_errno = saved_errno;
                        goto err;
                }
        } else if (lstat(p->fts_accpath, sbp)) {
                p->fts_errno = errno;
err:            memset(sbp, 0, sizeof(struct stat));
                return (FTS_NS);
        }

        if (S_ISDIR(sbp->st_mode)) {
                if (ISDOT(p->fts_name))
                        return (FTS_DOT);

#if _LGPL_PACKAGE
                {
                  /*
                   * Cycle detection is done by brute force when the directory
                   * is first encountered.  If the tree gets deep enough or the
                   * number of symbolic links to directories is high enough,
                   * something faster might be worthwhile.
                   */
                  FTSENT *t;

                  for (t = p->fts_parent;
                       t->fts_level >= FTS_ROOTLEVEL; t = t->fts_parent)
                    if (sbp->st_ino == t->fts_statp->st_ino
                        && sbp->st_dev == t->fts_statp->st_dev)
                      {
                        p->fts_cycle = t;
                        return (FTS_DC);
                      }
                }
#endif

                return (FTS_D);
        }
        if (S_ISLNK(sbp->st_mode))
                return (FTS_SL);
        if (S_ISREG(sbp->st_mode))
                return (FTS_F);
        return (FTS_DEFAULT);
}

static int
fts_compar (void const *a, void const *b)
{
  /* Convert A and B to the correct types, to pacify the compiler, and
     for portability to bizarre hosts where "void const *" and "FTSENT
     const **" differ in runtime representation.  The comparison
     function cannot modify *a and *b, but there is no compile-time
     check for this.  */
  FTSENT const **pa = (FTSENT const **) a;
  FTSENT const **pb = (FTSENT const **) b;
  return pa[0]->fts_fts->fts_compar (pa, pb);
}

static FTSENT *
internal_function
fts_sort (FTS *sp, FTSENT *head, register size_t nitems)
{
        register FTSENT **ap, *p;

        /* On most modern hosts, void * and FTSENT ** have the same
           run-time representation, and one can convert sp->fts_compar to
           the type qsort expects without problem.  Use the heuristic that
           this is OK if the two pointer types are the same size, and if
           converting FTSENT ** to long int is the same as converting
           FTSENT ** to void * and then to long int.  This heuristic isn't
           valid in general but we don't know of any counterexamples.  */
        FTSENT *dummy;
        int (*compare) (void const *, void const *) =
          ((sizeof &dummy == sizeof (void *)
            && (long int) &dummy == (long int) (void *) &dummy)
           ? (int (*) (void const *, void const *)) sp->fts_compar
           : fts_compar);

        /*
         * Construct an array of pointers to the structures and call qsort(3).
         * Reassemble the array in the order returned by qsort.  If unable to
         * sort for memory reasons, return the directory entries in their
         * current order.  Allocate enough space for the current needs plus
         * 40 so don't realloc one entry at a time.
         */
        if (nitems > sp->fts_nitems) {
                struct _ftsent **a;

                sp->fts_nitems = nitems + 40;
                if (SIZE_MAX / sizeof *a < sp->fts_nitems
                    || ! (a = realloc (sp->fts_array,
                                       sp->fts_nitems * sizeof *a))) {
                        free(sp->fts_array);
                        sp->fts_array = NULL;
                        sp->fts_nitems = 0;
                        return (head);
                }
                sp->fts_array = a;
        }
        for (ap = sp->fts_array, p = head; p; p = p->fts_link)
                *ap++ = p;
        qsort((void *)sp->fts_array, nitems, sizeof(FTSENT *), compare);
        for (head = *(ap = sp->fts_array); --nitems; ++ap)
                ap[0]->fts_link = ap[1];
        ap[0]->fts_link = NULL;
        return (head);
}

static FTSENT *
internal_function
fts_alloc (FTS *sp, const char *name, register size_t namelen)
{
        register FTSENT *p;
        size_t len;

        /*
         * The file name is a variable length array.  Allocate the FTSENT
         * structure and the file name in one chunk.
         */
        len = sizeof(FTSENT) + namelen;
        if ((p = malloc(len)) == NULL)
                return (NULL);

        /* Copy the name and guarantee NUL termination. */
        memmove(p->fts_name, name, namelen);
        p->fts_name[namelen] = '\0';

        p->fts_namelen = namelen;
        p->fts_fts = sp;
        p->fts_path = sp->fts_path;
        p->fts_errno = 0;
        p->fts_flags = 0;
        p->fts_instr = FTS_NOINSTR;
        p->fts_number = 0;
        p->fts_pointer = NULL;
        return (p);
}

static void
internal_function
fts_lfree (register FTSENT *head)
{
        register FTSENT *p;

        /* Free a linked list of structures. */
        while ((p = head)) {
                head = head->fts_link;
                free(p);
        }
}

/*
 * Allow essentially unlimited file name lengths; find, rm, ls should
 * all work on any tree.  Most systems will allow creation of file
 * names much longer than MAXPATHLEN, even though the kernel won't
 * resolve them.  Add the size (not just what's needed) plus 256 bytes
 * so don't realloc the file name 2 bytes at a time.
 */
static bool
internal_function
fts_palloc (FTS *sp, size_t more)
{
        char *p;
        size_t new_len = sp->fts_pathlen + more + 256;

        /*
         * See if fts_pathlen would overflow.
         */
        if (new_len < sp->fts_pathlen) {
                if (sp->fts_path) {
                        free(sp->fts_path);
                        sp->fts_path = NULL;
                }
                sp->fts_path = NULL;
                __set_errno (ENAMETOOLONG);
                return false;
        }
        sp->fts_pathlen = new_len;
        p = realloc(sp->fts_path, sp->fts_pathlen);
        if (p == NULL) {
                free(sp->fts_path);
                sp->fts_path = NULL;
                return false;
        }
        sp->fts_path = p;
        return true;
}

/*
 * When the file name is realloc'd, have to fix all of the pointers in
 *  structures already returned.
 */
static void
internal_function
fts_padjust (FTS *sp, FTSENT *head)
{
        FTSENT *p;
        char *addr = sp->fts_path;

#define ADJUST(p) do {                                                  \
        if ((p)->fts_accpath != (p)->fts_name) {                        \
                (p)->fts_accpath =                                      \
                    (char *)addr + ((p)->fts_accpath - (p)->fts_path);  \
        }                                                               \
        (p)->fts_path = addr;                                           \
} while (0)
        /* Adjust the current set of children. */
        for (p = sp->fts_child; p; p = p->fts_link)
                ADJUST(p);

        /* Adjust the rest of the tree, including the current level. */
        for (p = head; p->fts_level >= FTS_ROOTLEVEL;) {
                ADJUST(p);
                p = p->fts_link ? p->fts_link : p->fts_parent;
        }
}

static size_t
internal_function
fts_maxarglen (char * const *argv)
{
        size_t len, max;

        for (max = 0; *argv; ++argv)
                if ((len = strlen(*argv)) > max)
                        max = len;
        return (max + 1);
}

/*
 * Change to dir specified by fd or file name without getting
 * tricked by someone changing the world out from underneath us.
 * Assumes p->fts_statp->st_dev and p->fts_statp->st_ino are filled in.
 */
static int
internal_function
fts_safe_changedir (FTS *sp, FTSENT *p, int fd, char const *dir)
{
        int ret, oerrno, newfd;
        struct stat sb;

        newfd = fd;
        if (ISSET(FTS_NOCHDIR))
                return (0);
        if (fd < 0 && (newfd = diropen (dir)) < 0)
                return (-1);
        if (fstat(newfd, &sb)) {
                ret = -1;
                goto bail;
        }
        if (p->fts_statp->st_dev != sb.st_dev
            || p->fts_statp->st_ino != sb.st_ino) {
                __set_errno (ENOENT);           /* disinformation */
                ret = -1;
                goto bail;
        }
        ret = fchdir(newfd);
bail:
        oerrno = errno;
        if (fd < 0)
                (void)close(newfd);
        __set_errno (oerrno);
        return (ret);
}