GDir: add some glib-private APIs

Add a simple UNIX-only API that is used to create a GDir object from a
DIR* that is aquired using opendir() or fdopendir().

This makes it possible to use GDir with openat(), which in turn will
allow use of GDir in the existing GLocalFile implementation of
g_file_measure_disk_usage(), avoiding the current MSVC compatibility
problems there.

Also add an API similar to g_dir_open(), but without the GError handling
(since we want to create a better error message from inside of
glocalfile.c).

Thanks to Chun-wei Fan <fanchunwei@src.gnome.org> for portions of this
patch and for reviews.

https://bugzilla.gnome.org/show_bug.cgi?id=707787

glib/gdir.c

@@ -47,6 +47,8 @@
 #include "../build/win32/dirent/wdirent.c"
 #endif
 
+#include "glib-private.h" /* g_dir_open_with_errno, g_dir_new_from_dirp */
+
 /**
  * GDir:
  *
@@ -65,6 +67,57 @@ struct _GDir
 #endif
 };
 
+/*< private >
+ * g_dir_open_with_errno:
+ * @path: the path to the directory you are interested in.
+ * @flags: Currently must be set to 0. Reserved for future use.
+ *
+ * Opens a directory for reading.
+ *
+ * This function is equivalent to g_dir_open() except in the error case,
+ * errno will be set accordingly.
+ *
+ * This is useful if you want to construct your own error message.
+ *
+ * Returns: a newly allocated #GDir on success, or %NULL on failure,
+ *   with errno set accordingly.
+ *
+ * Since: 2.38
+ */
+GDir *
+g_dir_open_with_errno (const gchar *path,
+                       guint        flags)
+{
+  GDir dir;
+#ifdef G_OS_WIN32
+  gint saved_errno;
+  wchar_t *wpath;
+#endif
+
+  g_return_val_if_fail (path != NULL, NULL);
+
+#ifdef G_OS_WIN32
+  wpath = g_utf8_to_utf16 (path, -1, NULL, NULL, NULL);
+
+  g_return_val_if_fail (wpath != NULL, NULL);
+
+  dir.wdirp = _wopendir (wpath);
+  saved_errno = errno;
+  g_free (wpath);
+  errno = saved_errno;
+
+  if (dir.wdirp == NULL)
+    return NULL;
+#else
+  dir.dirp = opendir (path);
+
+  if (dir.dirp == NULL)
+    return NULL;
+#endif
+
+  return g_memdup (&dir, sizeof dir);
+}
+
 /**
  * g_dir_open:
  * @path: the path to the directory you are interested in. On Unix
@@ -87,67 +140,25 @@ g_dir_open (const gchar  *path,
             guint         flags,
             GError      **error)
 {
+  gint saved_errno;
   GDir *dir;
-  int errsv;
-#ifdef G_OS_WIN32
-  wchar_t *wpath;
-#else
-  gchar *utf8_path;
-#endif
 
-  g_return_val_if_fail (path != NULL, NULL);
+  dir = g_dir_open_with_errno (path, flags);
 
-#ifdef G_OS_WIN32
-  wpath = g_utf8_to_utf16 (path, -1, NULL, NULL, error);
+  if (dir == NULL)
+    {
+      gchar *utf8_path;
 
-  if (wpath == NULL)
-    return NULL;
+      saved_errno = errno;
 
-  dir = g_new (GDir, 1);
+      utf8_path = g_filename_to_utf8 (path, -1, NULL, NULL, NULL);
 
-  dir->wdirp = _wopendir (wpath);
-  g_free (wpath);
+      g_set_error (error, G_FILE_ERROR, g_file_error_from_errno (saved_errno),
+                   _("Error opening directory '%s': %s"), utf8_path, g_strerror (saved_errno));
+      g_free (utf8_path);
+    }
 
-  if (dir->wdirp)
-    return dir;
-
-  /* error case */
-  errsv = errno;
-
-  g_set_error (error,
-	       G_FILE_ERROR,
-	       g_file_error_from_errno (errsv),
-	       _("Error opening directory '%s': %s"),
-	       path, g_strerror (errsv));
-  
-  g_free (dir);
-      
-  return NULL;
-#else
-  dir = g_new (GDir, 1);
-
-  dir->dirp = opendir (path);
-
-  if (dir->dirp)
-    return dir;
-
-  /* error case */
-  errsv = errno;
-
-  utf8_path = g_filename_to_utf8 (path, -1,
-				  NULL, NULL, NULL);
-
-  g_set_error (error,
-               G_FILE_ERROR,
-               g_file_error_from_errno (errsv),
-               _("Error opening directory '%s': %s"),
-	       utf8_path, g_strerror (errsv));
-
-  g_free (utf8_path);
-  g_free (dir);
-
-  return NULL;
-#endif
+  return dir;
 }
 
 #if defined (G_OS_WIN32) && !defined (_WIN64)
@@ -180,6 +191,40 @@ g_dir_open (const gchar  *path,
 }
 #endif
 
+/*< private >
+ * g_dir_new_from_dirp:
+ * @dirp: a #DIR* created by opendir() or fdopendir()
+ *
+ * Creates a #GDir object from the DIR object that is created using
+ * opendir() or fdopendir().  The created #GDir assumes ownership of the
+ * passed-in #DIR pointer.
+ *
+ * @dirp must not be %NULL.
+ *
+ * This function never fails.
+ *
+ * Returns: a newly allocated #GDir, which should be closed using
+ *     g_dir_close().
+ *
+ * Since: 2.38
+ **/
+GDir *
+g_dir_new_from_dirp (gpointer dirp)
+{
+#ifdef G_OS_UNIX
+  GDir *dir;
+
+  g_return_val_if_fail (dirp != NULL, NULL);
+
+  dir = g_new (GDir, 1);
+  dir->dirp = dirp;
+
+  return dir;
+#else
+  g_assert_not_reached ();
+#endif
+}
+
 /**
  * g_dir_read_name:
  * @dir: a #GDir* created by g_dir_open()

glib/gdir.h

@@ -30,6 +30,10 @@
 
 #include <glib/gerror.h>
 
+#ifdef G_OS_UNIX
+#include <dirent.h>
+#endif
+
 G_BEGIN_DECLS
 
 typedef struct _GDir GDir;

glib/glib-private.c

@@ -43,7 +43,10 @@ glib__private__ (void)
     g_get_worker_context,
 
     g_check_setuid,
-    g_main_context_new_with_next_id
+    g_main_context_new_with_next_id,
+
+    g_dir_open_with_errno,
+    g_dir_new_from_dirp
   };
 
   return &table;

glib/glib-private.h

@@ -33,6 +33,9 @@ GLIB_AVAILABLE_IN_ALL
 gchar *_glib_get_locale_dir    (void);
 #endif
 
+GDir * g_dir_open_with_errno (const gchar *path, guint flags);
+GDir * g_dir_new_from_dirp (gpointer dirp);
+
 #define GLIB_PRIVATE_CALL(symbol) (glib__private__()->symbol)
 
 typedef struct {
@@ -49,6 +52,11 @@ typedef struct {
 
   gboolean              (* g_check_setuid)              (void);
   GMainContext *        (* g_main_context_new_with_next_id) (guint next_id);
+
+  GDir *                (* g_dir_open_with_errno)       (const gchar *path,
+                                                         guint        flags);
+  GDir *                (* g_dir_new_from_dirp)         (gpointer dirp);
+
   /* Add other private functions here, initialize them in glib-private.c */
 } GLibPrivateVTable;