posix: options: fs: separate file_system_r to its own file

Move the functionality of POSIX_FILE_SYSTEM_R to its own
compilation unit and remove the unnecessary dependency on
POSIX_FILE_SYSTEM.

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

lib/libc/Kconfig

@@ -86,6 +86,7 @@ config PICOLIBC
 	select LIBC_ERRNO if THREAD_LOCAL_STORAGE
 	select NEED_LIBC_MEM_PARTITION
 	select TC_PROVIDES_POSIX_C_LANG_SUPPORT_R
+	select TC_PROVIDES_POSIX_FILE_LOCKING
 	imply COMMON_LIBC_MALLOC
 	depends on PICOLIBC_SUPPORTED
 	help

lib/posix/options/CMakeLists.txt

@@ -71,6 +71,10 @@ if (NOT CONFIG_TC_PROVIDES_POSIX_FILE_SYSTEM)
   zephyr_library_sources_ifdef(CONFIG_POSIX_FILE_SYSTEM fs.c)
 endif()
 
+if (NOT CONFIG_TC_PROVIDES_POSIX_FILE_SYSTEM_R)
+  zephyr_library_sources_ifdef(CONFIG_POSIX_FILE_SYSTEM_R file_system_r.c)
+endif()
+
 zephyr_library_sources_ifdef(CONFIG_POSIX_FSYNC fsync.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MEMLOCK mlockall.c)
 zephyr_library_sources_ifdef(CONFIG_POSIX_MEMLOCK_RANGE mlock.c)

lib/posix/options/Kconfig

@@ -14,6 +14,7 @@ rsource "Kconfig.c_lang_r"
 rsource "Kconfig.c_lib_ext"
 rsource "Kconfig.device_io"
 rsource "Kconfig.fd_mgmt"
+rsource "Kconfig.file_system_r"
 rsource "Kconfig.fs"
 rsource "Kconfig.mem"
 rsource "Kconfig.mqueue"

lib/posix/options/Kconfig.file_system_r

@@ -0,0 +1,14 @@
+# Copyright (c) 2018 Intel Corporation
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config POSIX_FILE_SYSTEM_R
+	bool "Thread-Safe File System"
+	select FILE_SYSTEM
+	select FDTABLE
+	help
+	  Select 'y' here and Zephyr will provide an implementation of the POSIX_FILE_SYSTEM_R
+	  Option Group, consisting of readdir_r().
+
+	  For more informnation, please see
+	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html

lib/posix/options/Kconfig.fs

@@ -17,13 +17,4 @@ config POSIX_FILE_SYSTEM_ALIAS_FSTAT
 	help
 	  When selected via Kconfig, Zephyr will provide an alias for fstat() as _fstat().
 
-config POSIX_FILE_SYSTEM_R
-	bool "Thread-Safe File System"
-	help
-	  Select 'y' here and Zephyr will provide an implementation of the POSIX_FILE_SYSTEM_R
-	  Option Group, consisting of readdir_r().
-
-	  For more informnation, please see
-	  https://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_subprofiles.html
-
 endif # POSIX_FILE_SYSTEM

lib/posix/options/Kconfig.pthread

@@ -156,7 +156,7 @@ config POSIX_THREAD_PRIO_PROTECT
 
 config POSIX_THREAD_SAFE_FUNCTIONS
 	bool "POSIX thread-safe functions"
-	select POSIX_FILE_SYSTEM_R if POSIX_FILE_SYSTEM
+	select POSIX_FILE_SYSTEM_R
 	select POSIX_C_LANG_SUPPORT_R
 	help
 	  Select 'y' here to enable POSIX thread-safe functions including asctime_r(), ctime_r(),

lib/posix/options/file_system_r.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2024 Tenstorrent AI ULC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#undef _POSIX_C_SOURCE
+#define _POSIX_C_SOURCE 200809L
+
+#include "fs_priv.h"
+
+#include <errno.h>
+#include <limits.h>
+#include <string.h>
+
+#include <zephyr/fs/fs.h>
+#include <zephyr/posix/posix_features.h>
+#include <zephyr/posix/dirent.h>
+
+int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result)
+{
+	int rc;
+	struct fs_dirent de;
+	struct posix_fs_desc *const ptr = dirp;
+
+	if (result == NULL) {
+		return EINVAL;
+	}
+
+	if (entry == NULL) {
+		*result = NULL;
+		return EINVAL;
+	}
+
+	if (dirp == NULL) {
+		*result = NULL;
+		return EBADF;
+	}
+
+	rc = fs_readdir(&ptr->dir, &de);
+	if (rc < 0) {
+		*result = NULL;
+		return -rc;
+	}
+
+	strncpy(entry->d_name, de.name, MIN(sizeof(entry->d_name), sizeof(de.name)));
+	entry->d_name[sizeof(entry->d_name) - 1] = '\0';
+
+	if (entry->d_name[0] == '\0') {
+		*result = NULL;
+		return 0;
+	}
+
+	*result = entry;
+	return 0;
+}