[nautilus/max-name-length] directory: add method to query maximum filename length

[Ernestas Kulik <ernestask src gnome org>]

commit 0587e15f0a8ab928fbf9f1bee1f334173f7afb72
Author: Ernestas Kulik <ernestask gnome org>
Date:   Thu Feb 15 15:19:59 2018 +0200

    directory: add method to query maximum filename length
    
    This is to be used by a potential fix for
    https://gitlab.gnome.org/GNOME/nautilus/issues/148.

 src/nautilus-directory.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 src/nautilus-directory.h | 14 ++++++++++++++
 2 files changed, 57 insertions(+)
---
diff --git a/src/nautilus-directory.c b/src/nautilus-directory.c
index 0f6412e34..edf3ff43c 100644
--- a/src/nautilus-directory.c
+++ b/src/nautilus-directory.c
@@ -40,6 +40,8 @@
 #include <glib/gi18n.h>
 #include <gtk/gtk.h>
 
+#include <errno.h>
+
 enum
 {
     FILES_ADDED,
@@ -692,6 +694,47 @@ nautilus_directory_new_file_from_filename (NautilusDirectory *directory,
                                                                                               self_owned);
 }
 
+glong
+nautilus_directory_get_max_child_name_length (NautilusDirectory  *self,
+                                              GError            **error)
+{
+    g_autoptr (GFile) location = NULL;
+    g_autofree char *path = NULL;
+    glong result;
+
+    g_assert (NAUTILUS_IS_DIRECTORY (self));
+
+    location = nautilus_directory_get_location (self);
+    path = g_file_get_path (location);
+
+    g_assert (path != NULL);
+
+    /* pathconf() can return -1 if the maximum length is indefinite,
+     * in that case, errno is not set, so the only way to know is to
+     * check if errno is 0.
+     */
+    errno = 0;
+
+    result = pathconf (path, _PC_NAME_MAX);
+    if (result == -1)
+    {
+        int errsv;
+
+        errsv = errno;
+
+        if (errsv == 0)
+        {
+            return FILENAME_MAX;
+        }
+
+        g_set_error (error, G_IO_ERROR, g_io_error_from_errno (errsv),
+                     "Could not get maximum name length for children in %s: %s",
+                     path, g_strerror (errsv));
+    }
+
+    return result;
+}
+
 static GList *
 nautilus_directory_provider_get_all (void)
 {
diff --git a/src/nautilus-directory.h b/src/nautilus-directory.h
index a16b9c43d..076be0ac6 100644
--- a/src/nautilus-directory.h
+++ b/src/nautilus-directory.h
@@ -252,4 +252,18 @@ NautilusFile *     nautilus_directory_new_file_from_filename   (NautilusDirector
                                                                 const char        *filename,
                                                                 gboolean           self_owned);
 
+/**
+ * nautilus_directory_get_max_child_name_length:
+ * @directory: a #NautilusDirectory
+ * @error: (nullable): a #GError or %NULL
+ *
+ * Gets the maximum file name length for files inside @directory.
+ *
+ * This call does blocking I/O.
+ *
+ * Returns: The maximum file name length in bytes or -1 if an error occured.
+ */
+glong nautilus_directory_get_max_child_name_length (NautilusDirectory  *directory,
+                                                    GError            **error);
+
 #endif /* NAUTILUS_DIRECTORY_H */