- The default is to use the constant-memory lazy way. */
-# define FTS_TIGHT_CYCLE_CHECK 0x0100
-
-# define FTS_OPTIONMASK 0x01ff /* valid user option mask */
-
-# define FTS_NAMEONLY 0x1000 /* (private) child names only */
-# define FTS_STOP 0x2000 /* (private) unrecoverable error */
- int fts_options; /* fts_open options, global flags */
-
- /* This data structure records the directories between a starting
- point and the current directory. I.e., a directory is recorded
- here IFF we have visited it once, but we have not yet completed
- processing of all its entries. Every time we visit a new directory,
- we add that directory to this set. When we finish with a directory
- (usually by visiting it a second time), we remove it from this
- set. Each entry in this data structure is a device/inode pair.
- This data structure is used to detect directory cycles efficiently
- and promptly even when the depth of a hierarchy is in the tens
- of thousands. Lazy checking, as done by GNU rm via cycle-check.c,
- wouldn't be appropriate for du. */
- struct hash_table *active_dir_ht;
- struct cycle_check_state *cycle_state;
+ 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
+
+ /* 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
+
+ /* Historically, for each directory that fts initially encounters, it would
+ open it, read all entries, and stat each entry, storing the results, and
+ then it would process the first entry. But that behavior is bad for
+ locality of reference, and also causes trouble with inode-simulating
+ file systems like FAT, CIFS, FUSE-based ones, etc., when entries from
+ their name/inode cache are flushed too early.
+ Use this flag to make fts_open and fts_read defer the stat/lstat/fststat
+ of each entry until it is actually processed. However, note that if you
+ use this option and also specify a comparison function, that function may
+ not examine any data via fts_statp. However, when fts_statp->st_mode is
+ nonzero, the S_IFMT type bits are valid, with mapped dirent.d_type data.
+ Of course, that happens only on file systems that provide useful
+ dirent.d_type data. */
+# define FTS_DEFER_STAT 0x0400
+
+# define FTS_OPTIONMASK 0x07ff /* valid user option mask */
+
+# define FTS_NAMEONLY 0x1000 /* (private) child names only */
+# define FTS_STOP 0x2000 /* (private) unrecoverable error */
+ int fts_options; /* fts_open options, global flags */
+
+ /* Map a directory's device number to a boolean. The boolean is
+ true if for that file system (type determined by a single fstatfs
+ call per FS) st_nlink can be used to calculate the number of
+ sub-directory entries in a directory.
+ Using this table is an optimization that permits us to look up
+ file system type on a per-inode basis at the minimal cost of
+ calling fstatfs only once per traversed device. */
+ struct hash_table *fts_leaf_optimization_works_ht;
+
+ union {
+ /* This data structure is used if FTS_TIGHT_CYCLE_CHECK is
+ specified. It records the directories between a starting
+ point and the current directory. I.e., a directory is
+ recorded here IFF we have visited it once, but we have not
+ yet completed processing of all its entries. Every time we
+ visit a new directory, we add that directory to this set.
+ When we finish with a directory (usually by visiting it a
+ second time), we remove it from this set. Each entry in
+ this data structure is a device/inode pair. This data
+ structure is used to detect directory cycles efficiently and
+ promptly even when the depth of a hierarchy is in the tens
+ of thousands. */
+ struct hash_table *ht;
+
+ /* 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;
+
+ /* A stack of the file descriptors corresponding to the
+ most-recently traversed parent directories.
+ Currently used only in FTS_CWDFD mode. */
+ I_ring fts_fd_ring;