* lib/regex_internal.c (re_string_reconstruct): Handle

[gnulib.git] / lib / fts_.h

diff --git a/lib/fts_.h b/lib/fts_.h
index 4bf903b..2843107 100644 (file)
--- a/lib/fts_.h
+++ b/lib/fts_.h
@@ -1,6 +1,6 @@
 /* Traverse a file hierarchy.
 
-   Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2005, 2006 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
@@ -73,8 +73,10 @@ typedef struct {
        dev_t fts_dev;                  /* starting device # */
        char *fts_path;                 /* file name for this descent */
        int fts_rfd;                    /* fd for root */
+       int fts_cwd_fd;                 /* the file descriptor on which the
+                                          virtual cwd is open, or AT_FDCWD */
        size_t fts_pathlen;             /* sizeof(path) */
-       size_t fts_nitems;                      /* elements in the sort array */
+       size_t fts_nitems;              /* elements in the sort array */
        int (*fts_compar) (struct _ftsent const **, struct _ftsent const **);
                                        /* compare fn */
 
@@ -88,7 +90,8 @@ typedef struct {
 # define FTS_WHITEOUT  0x0080          /* return whiteout information */
 
   /* There are two ways to detect cycles.
-     The lazy way, with which one may process a directory that is a
+     The lazy way (which works only with FTS_PHYSICAL),
+     with which one may process a directory that is a
      part of the cycle several times before detecting the cycle.
      The `tight' way, whereby fts uses more memory (proportional
      to number of `active' directories, aka distance from root
@@ -96,10 +99,31 @@ typedef struct {
      to detect any cycle right away.  For example, du must use
      this option to avoid counting disk space in a cycle multiple
      times, but chown -R need not.
-     The default is to use the constant-memory lazy way. */
+     The default is to use the constant-memory lazy way, when possible
+     (see below).
+
+     However, with FTS_LOGICAL (when following symlinks, e.g., chown -L)
+     using lazy cycle detection is inadequate.  For example, traversing
+     a directory containing a symbolic link to a peer directory, it is
+     possible to encounter the same directory twice even though there
+     is no cycle:
+     dir
+     ...
+     slink -> dir
+     So, when FTS_LOGICAL is selected, we have to use a different
+     mode of cycle detection: FTS_TIGHT_CYCLE_CHECK.  */
 # define FTS_TIGHT_CYCLE_CHECK 0x0100
 
-# define FTS_OPTIONMASK        0x01ff          /* valid user option mask */
+  /* Use this flag to enable semantics with which the parent
+     application may be made both more efficient and more robust.
+     Whereas the default is to visit each directory in a recursive
+     traversal (via chdir), using this flag makes it so the initial
+     working directory is never changed.  Instead, these functions
+     perform the traversal via a virtual working directory, maintained
+     through the file descriptor member, fts_cwd_fd.  */
+# define FTS_CWDFD             0x0200
+
+# define FTS_OPTIONMASK        0x03ff          /* valid user option mask */
 
 # define FTS_NAMEONLY  0x1000          /* (private) child names only */
 # define FTS_STOP      0x2000          /* (private) unrecoverable error */
@@ -121,9 +145,10 @@ typedef struct {
                   of thousands.  */
                struct hash_table *ht;
 
-               /* This data structure uses lazy checking, as done by rm via
-                  cycle-check.c.  It's the default, but it's not appropriate
-                  for programs like du.  */
+               /* FIXME: rename these two members to have the fts_ prefix */
+               /* This data structure uses a lazy cycle-detection algorithm,
+                  as done by rm via cycle-check.c.  It's the default,
+                  but it's not appropriate for programs like du.  */
                struct cycle_check_state *state;
        } fts_cycle;
 # endif