dir-iterator: refactor state machine model
authorMatheus Tavares <matheus.bernardino@usp.br>
Wed, 10 Jul 2019 23:58:59 +0000 (20:58 -0300)
committerJunio C Hamano <gitster@pobox.com>
Thu, 11 Jul 2019 20:52:15 +0000 (13:52 -0700)
dir_iterator_advance() is a large function with two nested loops. Let's
improve its readability factoring out three functions and simplifying
its mechanics. The refactored model will no longer depend on
level.initialized and level.dir_state to keep track of the iteration
state and will perform on a single loop.

Also, dir_iterator_begin() currently does not check if the given string
represents a valid directory path. Since the refactored model will have
to stat() the given path at initialization, let's also check for this
kind of error and make dir_iterator_begin() return NULL, on failures,
with errno appropriately set. And add tests for this new behavior.

Improve documentation at dir-iteration.h and code comments at
dir-iterator.c to reflect the changes and eliminate possible
ambiguities.

Finally, adjust refs/files-backend.c to check for now possible
dir_iterator_begin() failures.

Original-patch-by: Daniel Ferreira <bnmvco@gmail.com>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dir-iterator.c
dir-iterator.h
refs/files-backend.c
t/helper/test-dir-iterator.c
t/t0066-dir-iterator.sh

index 0c88808..594fe4d 100644 (file)
@@ -4,8 +4,6 @@
 #include "dir-iterator.h"
 
 struct dir_iterator_level {
-       int initialized;
-
        DIR *dir;
 
        /*
@@ -13,16 +11,6 @@ struct dir_iterator_level {
         * (including a trailing '/'):
         */
        size_t prefix_len;
-
-       /*
-        * The last action that has been taken with the current entry
-        * (needed for directories, which have to be included in the
-        * iteration and also iterated into):
-        */
-       enum {
-               DIR_STATE_ITER,
-               DIR_STATE_RECURSE
-       } dir_state;
 };
 
 /*
@@ -34,9 +22,11 @@ struct dir_iterator_int {
        struct dir_iterator base;
 
        /*
-        * The number of levels currently on the stack. This is always
-        * at least 1, because when it becomes zero the iteration is
-        * ended and this struct is freed.
+        * The number of levels currently on the stack. After the first
+        * call to dir_iterator_begin(), if it succeeds to open the
+        * first level's dir, this will always be at least 1. Then,
+        * when it comes to zero the iteration is ended and this
+        * struct is freed.
         */
        size_t levels_nr;
 
@@ -50,113 +40,118 @@ struct dir_iterator_int {
        struct dir_iterator_level *levels;
 };
 
+/*
+ * Push a level in the iter stack and initialize it with information from
+ * the directory pointed by iter->base->path. It is assumed that this
+ * strbuf points to a valid directory path. Return 0 on success and -1
+ * otherwise, leaving the stack unchanged.
+ */
+static int push_level(struct dir_iterator_int *iter)
+{
+       struct dir_iterator_level *level;
+
+       ALLOC_GROW(iter->levels, iter->levels_nr + 1, iter->levels_alloc);
+       level = &iter->levels[iter->levels_nr++];
+
+       if (!is_dir_sep(iter->base.path.buf[iter->base.path.len - 1]))
+               strbuf_addch(&iter->base.path, '/');
+       level->prefix_len = iter->base.path.len;
+
+       level->dir = opendir(iter->base.path.buf);
+       if (!level->dir) {
+               if (errno != ENOENT) {
+                       warning_errno("error opening directory '%s'",
+                                     iter->base.path.buf);
+               }
+               iter->levels_nr--;
+               return -1;
+       }
+
+       return 0;
+}
+
+/*
+ * Pop the top level on the iter stack, releasing any resources associated
+ * with it. Return the new value of iter->levels_nr.
+ */
+static int pop_level(struct dir_iterator_int *iter)
+{
+       struct dir_iterator_level *level =
+               &iter->levels[iter->levels_nr - 1];
+
+       if (level->dir && closedir(level->dir))
+               warning_errno("error closing directory '%s'",
+                             iter->base.path.buf);
+       level->dir = NULL;
+
+       return --iter->levels_nr;
+}
+
+/*
+ * Populate iter->base with the necessary information on the next iteration
+ * entry, represented by the given dirent de. Return 0 on success and -1
+ * otherwise.
+ */
+static int prepare_next_entry_data(struct dir_iterator_int *iter,
+                                  struct dirent *de)
+{
+       strbuf_addstr(&iter->base.path, de->d_name);
+       /*
+        * We have to reset these because the path strbuf might have
+        * been realloc()ed at the previous strbuf_addstr().
+        */
+       iter->base.relative_path = iter->base.path.buf +
+                                  iter->levels[0].prefix_len;
+       iter->base.basename = iter->base.path.buf +
+                             iter->levels[iter->levels_nr - 1].prefix_len;
+
+       if (lstat(iter->base.path.buf, &iter->base.st)) {
+               if (errno != ENOENT)
+                       warning_errno("failed to stat '%s'", iter->base.path.buf);
+               return -1;
+       }
+
+       return 0;
+}
+
 int dir_iterator_advance(struct dir_iterator *dir_iterator)
 {
        struct dir_iterator_int *iter =
                (struct dir_iterator_int *)dir_iterator;
 
+       if (S_ISDIR(iter->base.st.st_mode)) {
+               if (push_level(iter) && iter->levels_nr == 0) {
+                       /* Pushing the first level failed */
+                       return dir_iterator_abort(dir_iterator);
+               }
+       }
+
+       /* Loop until we find an entry that we can give back to the caller. */
        while (1) {
+               struct dirent *de;
                struct dir_iterator_level *level =
                        &iter->levels[iter->levels_nr - 1];
-               struct dirent *de;
 
-               if (!level->initialized) {
-                       /*
-                        * Note: dir_iterator_begin() ensures that
-                        * path is not the empty string.
-                        */
-                       if (!is_dir_sep(iter->base.path.buf[iter->base.path.len - 1]))
-                               strbuf_addch(&iter->base.path, '/');
-                       level->prefix_len = iter->base.path.len;
-
-                       level->dir = opendir(iter->base.path.buf);
-                       if (!level->dir && errno != ENOENT) {
-                               warning_errno("error opening directory '%s'",
+               strbuf_setlen(&iter->base.path, level->prefix_len);
+               errno = 0;
+               de = readdir(level->dir);
+
+               if (!de) {
+                       if (errno)
+                               warning_errno("error reading directory '%s'",
                                              iter->base.path.buf);
-                               /* Popping the level is handled below */
-                       }
-
-                       level->initialized = 1;
-               } else if (S_ISDIR(iter->base.st.st_mode)) {
-                       if (level->dir_state == DIR_STATE_ITER) {
-                               /*
-                                * The directory was just iterated
-                                * over; now prepare to iterate into
-                                * it.
-                                */
-                               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;
-                               continue;
-                       } else {
-                               /*
-                                * The directory has already been
-                                * iterated over and iterated into;
-                                * we're done with it.
-                                */
-                       }
+                       else if (pop_level(iter) == 0)
+                               return dir_iterator_abort(dir_iterator);
+                       continue;
                }
 
-               if (!level->dir) {
-                       /*
-                        * This level is exhausted (or wasn't opened
-                        * successfully); pop up a level.
-                        */
-                       if (--iter->levels_nr == 0)
-                               return dir_iterator_abort(dir_iterator);
+               if (is_dot_or_dotdot(de->d_name))
+                       continue;
 
+               if (prepare_next_entry_data(iter, de))
                        continue;
-               }
 
-               /*
-                * Loop until we find an entry that we can give back
-                * to the caller:
-                */
-               while (1) {
-                       strbuf_setlen(&iter->base.path, level->prefix_len);
-                       errno = 0;
-                       de = readdir(level->dir);
-
-                       if (!de) {
-                               /* This level is exhausted; pop up a level. */
-                               if (errno) {
-                                       warning_errno("error reading directory '%s'",
-                                                     iter->base.path.buf);
-                               } else if (closedir(level->dir))
-                                       warning_errno("error closing directory '%s'",
-                                                     iter->base.path.buf);
-
-                               level->dir = NULL;
-                               if (--iter->levels_nr == 0)
-                                       return dir_iterator_abort(dir_iterator);
-                               break;
-                       }
-
-                       if (is_dot_or_dotdot(de->d_name))
-                               continue;
-
-                       strbuf_addstr(&iter->base.path, de->d_name);
-                       if (lstat(iter->base.path.buf, &iter->base.st) < 0) {
-                               if (errno != ENOENT)
-                                       warning_errno("failed to stat '%s'",
-                                                     iter->base.path.buf);
-                               continue;
-                       }
-
-                       /*
-                        * 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 ITER_OK;
-               }
+               return ITER_OK;
        }
 }
 
@@ -187,17 +182,32 @@ struct dir_iterator *dir_iterator_begin(const char *path)
 {
        struct dir_iterator_int *iter = xcalloc(1, sizeof(*iter));
        struct dir_iterator *dir_iterator = &iter->base;
-
-       if (!path || !*path)
-               BUG("empty path passed to dir_iterator_begin()");
+       int saved_errno;
 
        strbuf_init(&iter->base.path, PATH_MAX);
        strbuf_addstr(&iter->base.path, path);
 
        ALLOC_GROW(iter->levels, 10, iter->levels_alloc);
+       iter->levels_nr = 0;
 
-       iter->levels_nr = 1;
-       iter->levels[0].initialized = 0;
+       /*
+        * Note: stat already checks for NULL or empty strings and
+        * inexistent paths.
+        */
+       if (stat(iter->base.path.buf, &iter->base.st) < 0) {
+               saved_errno = errno;
+               goto error_out;
+       }
+
+       if (!S_ISDIR(iter->base.st.st_mode)) {
+               saved_errno = ENOTDIR;
+               goto error_out;
+       }
 
        return dir_iterator;
+
+error_out:
+       dir_iterator_abort(dir_iterator);
+       errno = saved_errno;
+       return NULL;
 }
index 970793d..9b4cb7a 100644 (file)
@@ -8,18 +8,22 @@
  *
  * Iterate over a directory tree, recursively, including paths of all
  * types and hidden paths. Skip "." and ".." entries and don't follow
- * symlinks except for the original path.
+ * symlinks except for the original path. Note that the original path
+ * is not included in the iteration.
  *
  * Every time dir_iterator_advance() is called, update the members of
  * the dir_iterator structure to reflect the next path in the
  * iteration. The order that paths are iterated over within a
- * directory is undefined, but directory paths are always iterated
- * over before the subdirectory contents.
+ * directory is undefined, directory paths are always given before
+ * their contents.
  *
  * A typical iteration looks like this:
  *
  *     int ok;
- *     struct iterator *iter = dir_iterator_begin(path);
+ *     struct dir_iterator *iter = dir_iterator_begin(path);
+ *
+ *     if (!iter)
+ *             goto error_handler;
  *
  *     while ((ok = dir_iterator_advance(iter)) == ITER_OK) {
  *             if (want_to_stop_iteration()) {
@@ -59,8 +63,9 @@ 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. On success, return a
+ * dir_iterator that holds the internal state of the iteration.
+ * In case of failure, return NULL and set errno accordingly.
  *
  * The iteration includes all paths under path, not including path
  * itself and not including "." or ".." entries.
index 63e55e6..7ed8104 100644 (file)
@@ -2143,13 +2143,22 @@ static struct ref_iterator_vtable files_reflog_iterator_vtable = {
 static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
                                                  const char *gitdir)
 {
-       struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
-       struct ref_iterator *ref_iterator = &iter->base;
+       struct dir_iterator *diter;
+       struct files_reflog_iterator *iter;
+       struct ref_iterator *ref_iterator;
        struct strbuf sb = STRBUF_INIT;
 
-       base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
        strbuf_addf(&sb, "%s/logs", gitdir);
-       iter->dir_iterator = dir_iterator_begin(sb.buf);
+
+       diter = dir_iterator_begin(sb.buf);
+       if(!diter)
+               return empty_ref_iterator_begin();
+
+       iter = xcalloc(1, sizeof(*iter));
+       ref_iterator = &iter->base;
+
+       base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable, 0);
+       iter->dir_iterator = diter;
        iter->ref_store = ref_store;
        strbuf_release(&sb);
 
index 84f50be..fab1ff6 100644 (file)
@@ -17,6 +17,11 @@ int cmd__dir_iterator(int argc, const char **argv)
 
        diter = dir_iterator_begin(path.buf);
 
+       if (!diter) {
+               printf("dir_iterator_begin failure: %d\n", errno);
+               exit(EXIT_FAILURE);
+       }
+
        while (dir_iterator_advance(diter) == ITER_OK) {
                if (S_ISDIR(diter->st.st_mode))
                        printf("[d] ");
index 59bce86..cc4b19c 100755 (executable)
@@ -52,4 +52,17 @@ test_expect_success 'dir-iterator should list files in the correct order' '
        test_cmp expected-pre-order-output actual-pre-order-output
 '
 
+test_expect_success 'begin should fail upon inexistent paths' '
+       test_must_fail test-tool dir-iterator ./inexistent-path \
+               >actual-inexistent-path-output &&
+       echo "dir_iterator_begin failure: 2" >expected-inexistent-path-output &&
+       test_cmp expected-inexistent-path-output actual-inexistent-path-output
+'
+
+test_expect_success 'begin should fail upon non directory paths' '
+       test_must_fail test-tool dir-iterator ./dir/b >actual-non-dir-output &&
+       echo "dir_iterator_begin failure: 20" >expected-non-dir-output &&
+       test_cmp expected-non-dir-output actual-non-dir-output
+'
+
 test_done