[PATCH v4 2/5] dir_iterator: iterate over dir after its contents

[Daniel Ferreira <bnmvco@gmail.com>]

Create an option for the dir_iterator API to iterate over subdirectories
only after having iterated through their contents. This feature was
predicted, although not implemented by 0fe5043 ("dir_iterator: new API
for iterating over a directory tree", 2016-06-18).

Add the "flags" parameter to dir_iterator_create, allowing for the
aforementioned "depth-first" iteration mode to be enabled. Currently,
the only acceptable flag is DIR_ITERATOR_DEPTH_FIRST.

This is useful for recursively removing a directory and calling rmdir()
on a directory only after all of its contents have been wiped.

Signed-off-by: Daniel Ferreira <bnmvco@gmail.com>
---
 dir-iterator.c | 46 ++++++++++++++++++++++++++++++++++++++++++----
 dir-iterator.h | 14 +++++++++++---
 2 files changed, 53 insertions(+), 7 deletions(-)

diff --git a/dir-iterator.c b/dir-iterator.c
index 853c040..545d333 100644
--- a/dir-iterator.c
+++ b/dir-iterator.c
@@ -48,6 +48,9 @@ struct dir_iterator_int {
 	 * that will be included in this iteration.
 	 */
 	struct dir_iterator_level *levels;
+
+	/* Holds the flags passed to dir_iterator_begin(). */
+	unsigned flags;
 };

 static inline void push_dir_level(struct dir_iterator_int *iter, struct dir_iterator_level *level)
@@ -114,12 +117,14 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			}

 			level->initialized = 1;
-		} else if (S_ISDIR(iter->base.st.st_mode)) {
+		} else if (S_ISDIR(iter->base.st.st_mode) &&
+		!iter->flags & DIR_ITERATOR_DEPTH_FIRST) {
 			if (level->dir_state == DIR_STATE_ITER) {
 				/*
 				 * The directory was just iterated
 				 * over; now prepare to iterate into
-				 * it.
+				 * it (unless an option is set for us
+				 * to do otherwise).
 				 */
 				push_dir_level(iter, level);
 				continue;
@@ -153,10 +158,27 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			de = readdir(level->dir);

 			if (!de) {
-				/* This level is exhausted; pop up a level. */
+				/* This level is exhausted  */
 				if (errno) {
 					warning("error reading directory %s: %s",
 						iter->base.path.buf, strerror(errno));
+				} else if (iter->flags & DIR_ITERATOR_DEPTH_FIRST) {
+					/* If we are handling dirpaths after their contents,
+					 * we have to iterate over the directory now that we'll
+					 * have finished iterating into it. */
+					level->dir = NULL;
+
+					if (pop_dir_level(iter, level) == 0)
+						return dir_iterator_abort(dir_iterator);
+
+					level = &iter->levels[iter->levels_nr - 1];
+					/* Remove a trailing slash */
+					strbuf_strip_suffix(&iter->base.path, "/");
+
+					if (set_iterator_data(iter, level))
+						continue;
+
+					return ITER_OK;
 				} else if (closedir(level->dir))
 					warning("error closing directory %s: %s",
 						iter->base.path.buf, strerror(errno));
@@ -175,8 +197,22 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			if (set_iterator_data(iter, level))
 				continue;

+			/*
+			 * If we want to iterate dirs after files, we shall
+			 * begin looking into them *before* we return the dir
+			 * itself.
+			 */
+			if (S_ISDIR(iter->base.st.st_mode) &&
+			iter->flags & DIR_ITERATOR_DEPTH_FIRST) {
+				push_dir_level(iter, level);
+				goto continue_outer_loop;
+			}
+
 			return ITER_OK;
 		}
+
+continue_outer_loop:
+		;
 	}
 }

@@ -201,7 +237,7 @@ int dir_iterator_abort(struct dir_iterator *dir_iterator)
 	return ITER_DONE;
 }

-struct dir_iterator *dir_iterator_begin(const char *path)
+struct dir_iterator *dir_iterator_begin(const char *path, unsigned flags)
 {
 	struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
 	struct dir_iterator *dir_iterator = &iter->base;
@@ -209,6 +245,8 @@ struct dir_iterator *dir_iterator_begin(const char *path)
 	if (!path || !*path)
 		die("BUG: empty path passed to dir_iterator_begin()");

+	iter->flags = flags;
+
 	strbuf_init(&iter->base.path, PATH_MAX);
 	strbuf_addstr(&iter->base.path, path);

diff --git a/dir-iterator.h b/dir-iterator.h
index 27739e6..28ff3df 100644
--- a/dir-iterator.h
+++ b/dir-iterator.h
@@ -38,6 +38,13 @@
  * dir_iterator_advance() again.
  */

+/* Possible flags for dir_iterator_begin().
+ *
+ * DIR_ITERATOR_DEPTH_FIRST: ensures subdirectories and their contents
+ * are iterated through before the containing directory.
+ */
+#define DIR_ITERATOR_DEPTH_FIRST (1 << 1)
+
 struct dir_iterator {
 	/* The current path: */
 	struct strbuf path;
@@ -57,15 +64,16 @@ struct dir_iterator {
 };

 /*
- * Start a directory iteration over path. Return a dir_iterator that
- * holds the internal state of the iteration.
+ * Start a directory iteration over path, with options specified in
+ * 'flags'. Return a dir_iterator that holds the internal state of
+ * the iteration.
  *
  * The iteration includes all paths under path, not including path
  * itself and not including "." or ".." entries.
  *
  * path is the starting directory. An internal copy will be made.
  */
-struct dir_iterator *dir_iterator_begin(const char *path);
+struct dir_iterator *dir_iterator_begin(const char *path, unsigned flags);

 /*
  * Advance the iterator to the first or next item and return ITER_OK.
--
2.7.4 (Apple Git-66)