Added fts support for traversing UNIX file hierarchies.

It is required by libdwfl in elfutils package.

Signed-off-by: Salvatore Cro <salvatore.cro at st.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 1145 insertions, 0 deletions

diff --git a/libc/misc/fts/fts.c b/libc/misc/fts/fts.c
new file mode 100644
index 000000000..ce5d1586b
--- /dev/null
+++ b/libc/misc/fts/fts.c
@@ -0,0 +1,1145 @@
+/*-
+ * 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.
+ */
+
+#include <sys/param.h>
+#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>
+
+#ifdef __UCLIBC_HAS_LFS__
+# include <_lfs_64.h>
+#else
+# define stat64 stat
+# define fstat64 fstat
+#endif
+
+/* 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 (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 int	 fts_palloc (FTS *, size_t) internal_function;
+static FTSENT	*fts_sort (FTS *, FTSENT *, int) internal_function;
+static u_short	 fts_stat (FTS *, FTSENT *, int) internal_function;
+static int      fts_safe_changedir (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) (const FTSENT **, const FTSENT **);
+{
+	register FTS *sp;
+	register FTSENT *p, *root;
+	register int nitems;
+	FTSENT *parent = NULL;
+	FTSENT *tmp = NULL;
+
+	/* 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 (*) (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
+	size_t maxarglen = fts_maxarglen(argv);
+	if (fts_palloc(sp, MAX(maxarglen, MAXPATHLEN)))
+		goto mem1;
+
+	/* Allocate/initialize root's parent. */
+	if (*argv != NULL) {
+		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. */
+		size_t len = strlen(*argv);
+		if (len == 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);
+	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;
+		sp->fts_cur = p;
+		goto name;
+	}
+
+	/* Move to the next node on this level. */
+next:	tmp = p;
+	if ((p = p->fts_link) != NULL) {
+		sp->fts_cur = p;
+		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 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 p;
+	}
+
+	/* Move up to the parent node. */
+	p = tmp->fts_parent;
+	sp->fts_cur = p;
+	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 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, nlinks, saved_errno,
+	    nostat, doadjust;
+	size_t maxlen;
+	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, _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;
+				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 0
+		/* Unreachable code.  cderrno is only ever set to a nonnull
+		   value if dirp is closed at the same time.  But then we
+		   cannot enter this loop.  */
+		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
+#endif
+		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);
+		fts_lfree(head);
+		return (NULL);
+	}
+
+	/* If didn't find anything, return NULL. */
+	if (!nitems) {
+		if (type == BREAD)
+			cur->fts_info = FTS_DP;
+		fts_lfree(head);
+		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;
+	size_t 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) {
+		free(sp->fts_path);
+		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 (fstat64(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);
+}