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fts.c

/*-
 * 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.
 */

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

#include <sys/param.h>
#include <include/sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <errno.h>
#include <fts.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


/* Largest alignment size needed, minus one.
   Usually long double is the worst case.  */
#ifndef ALIGNBYTES
#define ALIGNBYTES      (__alignof__ (long double) - 1)
#endif
/* Align P to that size.  */
#ifndef ALIGN
#define     ALIGN(p)    (((unsigned long int) (p) + ALIGNBYTES) & ~ALIGNBYTES)
#endif


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

#ifndef MAX
#define MAX(a, b) ({ __typeof__ (a) _a = (a); \
                     __typeof__ (b) _b = (b); \
                     _a > _b ? _a : _b; })
#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 */

FTS *
fts_open(argv, options, compar)
      char * const *argv;
      register int options;
      int (*compar) __P((const FTSENT **, const FTSENT **));
{
      register FTS *sp;
      register FTSENT *p, *root;
      register int nitems;
      FTSENT *parent, *tmp;
      int len;

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

      /* Allocate/initialize the stream */
      if ((sp = malloc((u_int)sizeof(FTS))) == NULL)
            return (NULL);
      memset(sp, 0, sizeof(FTS));
      sp->fts_compar = (int (*) __P((const void *, const void *))) 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 path space, and enough, in any case,
       * to hold the user's paths.
       */
#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 paths. */
            if ((len = strlen(*argv)) == 0) {
                  __set_errno (ENOENT);
                  goto mem3;
            }

            p = fts_alloc(sp, *argv, len);
            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));

            /* 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 using chdir(2), grab a file descriptor pointing to dot to ensure
       * that we can get back here; this could be avoided for some paths,
       * 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 = __open(".", O_RDONLY, 0)) < 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(sp, p)
      FTS *sp;
      register FTSENT *p;
{
      register int 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 path 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_dev;
}

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

      /*
       * 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, path 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)) {
            saved_errno = __fchdir(sp->fts_rfd) ? errno : 0;
            (void)__close(sp->fts_rfd);

            /* Set errno and return. */
            if (saved_errno != 0) {
                  /* Free up the stream pointer. */
                  free(sp);
                  __set_errno (saved_errno);
                  return (-1);
            }
      }

      /* Free up the stream pointer. */
      free(sp);
      return (0);
}

/*
 * Special case of "/" at the end of the path so that slashes aren't
 * appended which would cause paths 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(sp)
      register FTS *sp;
{
      register FTSENT *p, *tmp;
      register 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, 0);
            return (p);
      }

      /*
       * 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, 1);
            if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
                  if ((p->fts_symfd = __open(".", O_RDONLY, 0)) < 0) {
                        p->fts_errno = errno;
                        p->fts_info = FTS_ERR;
                  } else
                        p->fts_flags |= FTS_SYMFOLLOW;
            }
            return (p);
      }

      /* 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_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;
                  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);
                  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 paths 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);
                  return (sp->fts_cur = p);
            }

            /*
             * 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, 1);
                  if (p->fts_info == FTS_D && !ISSET(FTS_NOCHDIR)) {
                        if ((p->fts_symfd =
                            __open(".", O_RDONLY, 0)) < 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);
            return (sp->fts_cur = 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 pathname. */
      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)) {
                  SET(FTS_STOP);
                  return (NULL);
            }
      } 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);
                  SET(FTS_STOP);
                  return (NULL);
            }
            (void)__close(p->fts_symfd);
      } else if (!(p->fts_flags & FTS_DONTCHDIR) &&
               fts_safe_changedir(sp, p->fts_parent, -1, "..")) {
            SET(FTS_STOP);
            return (NULL);
      }
      p->fts_info = p->fts_errno ? FTS_ERR : FTS_DP;
      return (sp->fts_cur = 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(sp, p, instr)
      FTS *sp;
      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(sp, instr)
      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 path 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 = __open(".", O_RDONLY, 0)) < 0)
            return (NULL);
      sp->fts_child = fts_build(sp, instr);
      if (__fchdir(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(sp, type)
      register FTS *sp;
      int type;
{
      register struct dirent *dp;
      register FTSENT *p, *head;
      register int nitems;
      FTSENT *cur, *tail;
      DIR *dirp;
      void *oldaddr;
      int cderrno, descend, len, level, maxlen, nlinks, saved_errno,
          nostat, doadjust;
      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(path, flag) __opendir(path)
#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, -1 if we're doing stats on everything.
       */
      if (type == BNAMES) {
            nlinks = 0;
            /* Be quiet about nostat, GCC. */
            nostat = 0;
      } else if (ISSET(FTS_NOSTAT) && ISSET(FTS_PHYSICAL)) {
            nlinks = cur->fts_nlink - (ISSET(FTS_SEEDOT) ? 0 : 2);
            nostat = 1;
      } else {
            nlinks = -1;
            nostat = 0;
      }

#ifdef notdef
      (void)printf("nlinks == %d (cur: %d)\n", nlinks, cur->fts_nlink);
      (void)printf("NOSTAT %d PHYSICAL %d SEEDOT %d\n",
          ISSET(FTS_NOSTAT), ISSET(FTS_PHYSICAL), ISSET(FTS_SEEDOT));
#endif
      /*
       * 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 path
       * 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 = 0;
                  cderrno = errno;
                  (void)__closedir(dirp);
                  dirp = NULL;
            } else
                  descend = 1;
      } else
            descend = 0;

      /*
       * Figure out the max file name length that can be stored in the
       * current path -- the inner loop allocates more path as necessary.
       * We really wouldn't have to do the maxlen calculations here, we
       * could do them in fts_read before returning the path, 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 name into the path.
       */
      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 = 0;
      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, (int)_D_EXACT_NAMLEN (dp))) == NULL)
                  goto mem1;
            if (_D_EXACT_NAMLEN (dp) >= maxlen) {/* include space for NUL */
                  oldaddr = sp->fts_path;
                  if (fts_palloc(sp, _D_EXACT_NAMLEN (dp) + len + 1)) {
                        /*
                         * No more memory for path or structures.  Save
                         * errno, free up the current structure and the
                         * structures already allocated.
                         */
mem1:                   saved_errno = errno;
                        if (p)
                              free(p);
                        fts_lfree(head);
                        (void)__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 = 1;
                        if (ISSET(FTS_NOCHDIR))
                              cp = sp->fts_path + len;
                  }
                  maxlen = sp->fts_pathlen - len;
            }

            if (len + _D_EXACT_NAMLEN (dp) >= USHRT_MAX) {
                  /*
                   * In an FTSENT, fts_pathlen is a u_short so it is
                   * possible to wraparound here.  If we do, free up
                   * the current structure and the structures already
                   * allocated, then error out with ENAMETOOLONG.
                   */
                  free(p);
                  fts_lfree(head);
                  (void)__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 = len + _D_EXACT_NAMLEN (dp);

#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 defined DT_DIR && defined _DIRENT_HAVE_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, 0);

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

            /* 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)
            (void)__closedir(dirp);

      /*
       * If realloc() changed the address of the path, 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 path 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 path
       * 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);
}

static u_short
internal_function
fts_stat(sp, p, follow)
      FTS *sp;
      register FTSENT *p;
      int follow;
{
      register FTSENT *t;
      register dev_t dev;
      register ino_t ino;
      struct stat *sbp, sb;
      int saved_errno;

      /* If user needs stat info, stat buffer already allocated. */
      sbp = ISSET(FTS_NOSTAT) ? &sb : p->fts_statp;

#if defined FTS_WHITEOUT && 0
      /* check for whiteout */
      if (p->fts_flags & FTS_ISW) {
            if (sbp != &sb) {
                  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)) {
            /*
             * Set the device/inode.  Used to find cycles and check for
             * crossing mount points.  Also remember the link count, used
             * in fts_build to limit the number of stat calls.  It is
             * understood that these fields are only referenced if fts_info
             * is set to FTS_D.
             */
            dev = p->fts_dev = sbp->st_dev;
            ino = p->fts_ino = sbp->st_ino;
            p->fts_nlink = sbp->st_nlink;

            if (ISDOT(p->fts_name))
                  return (FTS_DOT);

            /*
             * 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.
             */
            for (t = p->fts_parent;
                t->fts_level >= FTS_ROOTLEVEL; t = t->fts_parent)
                  if (ino == t->fts_ino && dev == t->fts_dev) {
                        p->fts_cycle = t;
                        return (FTS_DC);
                  }
            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 FTSENT *
internal_function
fts_sort(sp, head, nitems)
      FTS *sp;
      FTSENT *head;
      register int nitems;
{
      register FTSENT **ap, *p;

      /*
       * 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 ((a = realloc(sp->fts_array,
                (size_t)(sp->fts_nitems * sizeof(FTSENT *)))) == NULL) {
                  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 *), sp->fts_compar);
      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(sp, name, namelen)
      FTS *sp;
      const char *name;
      register int namelen;
{
      register FTSENT *p;
      size_t len;

      /*
       * The file name is a variable length array and no stat structure is
       * necessary if the user has set the nostat bit.  Allocate the FTSENT
       * structure, the file name and the stat structure in one chunk, but
       * be careful that the stat structure is reasonably aligned.  Since the
       * fts_name field is declared to be of size 1, the fts_name pointer is
       * namelen + 2 before the first possible address of the stat structure.
       */
      len = sizeof(FTSENT) + namelen;
      if (!ISSET(FTS_NOSTAT))
            len += sizeof(struct stat) + ALIGNBYTES;
      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';

      if (!ISSET(FTS_NOSTAT))
            p->fts_statp = (struct stat *)ALIGN(p->fts_name + namelen + 2);
      p->fts_namelen = namelen;
      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(head)
      register FTSENT *head;
{
      register FTSENT *p;

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

/*
 * Allow essentially unlimited paths; find, rm, ls should all work on any tree.
 * Most systems will allow creation of paths 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 path 2 bytes at a time.
 */
static int
internal_function
fts_palloc(sp, more)
      FTS *sp;
      size_t more;
{
      char *p;

      sp->fts_pathlen += more + 256;
      /*
       * Check for possible wraparound.  In an FTS, fts_pathlen is
       * a signed int but in an FTSENT it is an unsigned short.
       * We limit fts_pathlen to USHRT_MAX to be safe in both cases.
       */
      if (sp->fts_pathlen < 0 || sp->fts_pathlen >= USHRT_MAX) {
            if (sp->fts_path) {
                  free(sp->fts_path);
                  sp->fts_path = NULL;
            }
            sp->fts_path = NULL;
            __set_errno (ENAMETOOLONG);
            return (1);
      }
      p = realloc(sp->fts_path, sp->fts_pathlen);
      if (p == NULL) {
            free(sp->fts_path);
            sp->fts_path = NULL;
            return 1;
      }
      sp->fts_path = p;
      return 0;
}

/*
 * When the path is realloc'd, have to fix all of the pointers in structures
 * already returned.
 */
static void
internal_function
fts_padjust(sp, head)
      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(argv)
      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 p->fts_accpath without getting
 * tricked by someone changing the world out from underneath us.
 * Assumes p->fts_dev and p->fts_ino are filled in.
 */
static int
internal_function
fts_safe_changedir(sp, p, fd, path)
      FTS *sp;
      FTSENT *p;
      int fd;
      const char *path;
{
      int ret, oerrno, newfd;
      struct stat64 sb;

      newfd = fd;
      if (ISSET(FTS_NOCHDIR))
            return (0);
      if (fd < 0 && (newfd = __open(path, O_RDONLY, 0)) < 0)
            return (-1);
      if (__fxstat64(_STAT_VER, newfd, &sb)) {
            ret = -1;
            goto bail;
      }
      if (p->fts_dev != sb.st_dev || p->fts_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);
}

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