[PATCH v3 1/2] [GSoC] dir_iterator: iterate over dir after its contents

[Daniel Ferreira <bnmvco@gmail.com>]

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

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

An "options" member has been added to the dir_iterator struct. It
contains the "iterate_dirs_after_files" flag, that enables the feature
when set to 1. Default behavior continues to be iterating over directory
paths before its contents.

Two inline functions have been added to dir_iterator's code to avoid
code repetition inside dir_iterator_advance() and make code more clear.

No particular functions or wrappers for setting the options struct's
fields have been added to avoid either breaking the current dir_iterator
API or over-engineering an extremely simple option architecture.

Signed-off-by: Daniel Ferreira <bnmvco@gmail.com>
---
 dir-iterator.c | 100 ++++++++++++++++++++++++++++++++++++++++++++-------------
 dir-iterator.h |   7 ++++
 2 files changed, 84 insertions(+), 23 deletions(-)

diff --git a/dir-iterator.c b/dir-iterator.c
index 34182a9..833d56a 100644
--- a/dir-iterator.c
+++ b/dir-iterator.c
@@ -50,6 +50,43 @@ struct dir_iterator_int {
 	struct dir_iterator_level *levels;
 };

+static inline void push_dir_level(struct dir_iterator_int *iter, struct dir_iterator_level *level)
+{
+	level->dir_state = DIR_STATE_RECURSE;
+	ALLOC_GROW(iter->levels, iter->levels_nr + 1,
+		   iter->levels_alloc);
+	level = &iter->levels[iter->levels_nr++];
+	level->initialized = 0;
+}
+
+static inline int pop_dir_level(struct dir_iterator_int *iter, struct dir_iterator_level *level)
+{
+	return --iter->levels_nr;
+}
+
+static inline int set_iterator_data(struct dir_iterator_int *iter, struct dir_iterator_level *level)
+{
+	if (lstat(iter->base.path.buf, &iter->base.st) < 0) {
+		if (errno != ENOENT)
+			warning("error reading path '%s': %s",
+				iter->base.path.buf,
+				strerror(errno));
+		return -1;
+	}
+
+	/*
+	 * We have to set these each time because
+	 * the path strbuf might have been realloc()ed.
+	 */
+	iter->base.relative_path =
+		iter->base.path.buf + iter->levels[0].prefix_len;
+	iter->base.basename =
+		iter->base.path.buf + level->prefix_len;
+	level->dir_state = DIR_STATE_ITER;
+
+	return 0;
+}
+
 int dir_iterator_advance(struct dir_iterator *dir_iterator)
 {
 	struct dir_iterator_int *iter =
@@ -77,18 +114,16 @@ 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->base.options.iterate_dirs_after_files) {
 			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).
 				 */
-				level->dir_state = DIR_STATE_RECURSE;
-				ALLOC_GROW(iter->levels, iter->levels_nr + 1,
-					   iter->levels_alloc);
-				level = &iter->levels[iter->levels_nr++];
-				level->initialized = 0;
+				push_dir_level(iter, level);
 				continue;
 			} else {
 				/*
@@ -104,7 +139,7 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 			 * This level is exhausted (or wasn't opened
 			 * successfully); pop up a level.
 			 */
-			if (--iter->levels_nr == 0)
+			if (pop_dir_level(iter, level) == 0)
 				return dir_iterator_abort(dir_iterator);

 			continue;
@@ -120,16 +155,33 @@ 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->base.options.iterate_dirs_after_files) {
+					/* 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));

 				level->dir = NULL;
-				if (--iter->levels_nr == 0)
+				if (pop_dir_level(iter, level) == 0)
 					return dir_iterator_abort(dir_iterator);
 				break;
 			}
@@ -138,26 +190,26 @@ int dir_iterator_advance(struct dir_iterator *dir_iterator)
 				continue;

 			strbuf_addstr(&iter->base.path, de->d_name);
-			if (lstat(iter->base.path.buf, &iter->base.st) < 0) {
-				if (errno != ENOENT)
-					warning("error reading path '%s': %s",
-						iter->base.path.buf,
-						strerror(errno));
+
+			if (set_iterator_data(iter, level))
 				continue;
-			}

 			/*
-			 * We have to set these each time because
-			 * the path strbuf might have been realloc()ed.
+			 * If we want to iterate dirs after files, we shall
+			 * begin looking into them *before* we return the dir
+			 * itself.
 			 */
-			iter->base.relative_path =
-				iter->base.path.buf + iter->levels[0].prefix_len;
-			iter->base.basename =
-				iter->base.path.buf + level->prefix_len;
-			level->dir_state = DIR_STATE_ITER;
+			if (S_ISDIR(iter->base.st.st_mode) &&
+			iter->base.options.iterate_dirs_after_files) {
+				push_dir_level(iter, level);
+				goto continue_outer_loop;
+			}

 			return ITER_OK;
 		}
+
+continue_outer_loop:
+		;
 	}
 }

@@ -190,6 +242,8 @@ struct dir_iterator *dir_iterator_begin(const char *path)
 	if (!path || !*path)
 		die("BUG: empty path passed to dir_iterator_begin()");

+	iter->base.options.iterate_dirs_after_files = 0;
+
 	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..4304913 100644
--- a/dir-iterator.h
+++ b/dir-iterator.h
@@ -38,7 +38,14 @@
  * dir_iterator_advance() again.
  */

+struct dir_iterator_options {
+	unsigned iterate_dirs_after_files : 1;
+};
+
 struct dir_iterator {
+	/* Options for dir_iterator */
+	struct dir_iterator_options options;
+
 	/* The current path: */
 	struct strbuf path;

--
2.7.4 (Apple Git-66)