posix: fs: implement readdir_r

Add implementation for `readdir_r()`.

Signed-off-by: Yong Cong Sin <[email protected]>

Author: ycsin

doc/services/portability/posix/option_groups/index.rst

@@ -997,7 +997,7 @@ Enable this option with :kconfig:option:`CONFIG_POSIX_THREAD_SAFE_FUNCTIONS`.
     putc_unlocked(),
     putchar_unlocked(),
     rand_r(), yes
-    readdir_r(),
+    readdir_r(), yes
     strerror_r(), yes
     strtok_r(), yes
 

include/zephyr/posix/dirent.h

@@ -27,6 +27,8 @@ struct dirent {
 DIR *opendir(const char *dirname);
 int closedir(DIR *dirp);
 struct dirent *readdir(DIR *dirp);
+int readdir_r(DIR *ZRESTRICT dirp, struct dirent *ZRESTRICT entry,
+	      struct dirent **ZRESTRICT result);
 
 #ifdef __cplusplus
 }

lib/posix/options/fs.c

@@ -314,6 +314,40 @@ struct dirent *readdir(DIR *dirp)
 	return &pdirent;
 }
 
+#ifdef CONFIG_POSIX_THREAD_SAFE_FUNCTIONS
+int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result)
+{
+	struct dirent *dir;
+
+	errno = 0;
+
+	dir = readdir(dirp);
+	if (dir == NULL) {
+		int error = errno;
+
+		if (error != 0) {
+			if (result != NULL) {
+				*result = NULL;
+			}
+
+			return 0;
+		} else {
+			return error;
+		}
+	}
+
+	if (entry != NULL) {
+		memcpy(entry, dir, sizeof(struct dirent));
+	}
+
+	if (result != NULL) {
+		*result = entry;
+	}
+
+	return 0;
+}
+#endif /* CONFIG_POSIX_THREAD_SAFE_FUNCTIONS */
+
 /**
  * @brief Rename a file.
  *

tests/posix/fs/src/test_fs_dir.c

@@ -51,7 +51,21 @@ static int test_mkdir(void)
 	return res;
 }
 
-static int test_lsdir(const char *path)
+static struct dirent *readdir_wrap(DIR *dirp, bool thread_safe)
+{
+	if (thread_safe) {
+		struct dirent *entry = NULL;
+		struct dirent *result = NULL;
+
+		zassert_ok(readdir_r(dirp, entry, &result));
+
+		return result;
+	} else {
+		return readdir(dirp);
+	}
+}
+
+static int test_lsdir(const char *path, bool thread_safe)
 {
 	DIR *dirp;
 	int res = 0;
@@ -69,7 +83,7 @@ static int test_lsdir(const char *path)
 	TC_PRINT("\nListing dir %s:\n", path);
 	/* Verify fs_readdir() */
 	errno = 0;
-	while ((entry = readdir(dirp)) != NULL) {
+	while ((entry = readdir_wrap(dirp, thread_safe)) != NULL) {
 		if (entry->d_name[0] == 0) {
 			res = -EIO;
 			break;
@@ -124,5 +138,15 @@ ZTEST(posix_fs_dir_test, test_fs_readdir)
 {
 	/* FIXME: restructure tests as per #46897 */
 	zassert_true(test_mkdir() == TC_PASS);
-	zassert_true(test_lsdir(TEST_DIR) == TC_PASS);
+	zassert_true(test_lsdir(TEST_DIR, false) == TC_PASS);
+}
+
+/**
+ * Same test as `test_fs_readdir`, but use thread-safe `readdir_r()` function
+ */
+ZTEST(posix_fs_dir_test, test_fs_readdir_threadsafe)
+{
+	/* FIXME: restructure tests as per #46897 */
+	zassert_true(test_mkdir() == TC_PASS);
+	zassert_true(test_lsdir(TEST_DIR, true) == TC_PASS);
 }

tests/posix/headers/src/dirent_h.c

@@ -31,7 +31,7 @@ ZTEST(posix_headers, test_dirent_h)
 	/* zassert_not_null(fdopendir); */ /* not implemented */
 	zassert_not_null(opendir);
 	zassert_not_null(readdir);
-	/* zassert_not_null(readdir_r); */ /* not implemented */
+	zassert_not_null(readdir_r);
 	/* zassert_not_null(rewinddir); */ /* not implemented */
 	/* zassert_not_null(scandir); */   /* not implemented */
 	/* zassert_not_null(seekdir); */   /* not implemented */