Extract opendirat() helper function into libotutil

We were duplicating the code to do an opendirat() in a few places.

src/libotutil/ot-fs-utils.c

@@ -0,0 +1,50 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "ot-fs-utils.h"
+
+int
+ot_opendirat (int dfd, const char *path, gboolean follow)
+{
+  int flags = O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC | O_NOCTTY;
+  if (!follow)
+    flags |= O_NOFOLLOW;
+  return openat (dfd, path, flags);
+}
+
+gboolean
+ot_gopendirat (int             dfd,
+               const char     *path,
+               gboolean        follow,
+               int            *out_fd,
+               GError        **error)
+{
+  int ret = ot_opendirat (dfd, path, follow);
+  if (ret == -1)
+    {
+      ot_util_set_error_from_errno (error, errno);
+      return FALSE;
+    }
+  *out_fd = ret;
+  return TRUE;
+}
+

src/libotutil/ot-fs-utils.h

@@ -0,0 +1,35 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include "ot-unix-utils.h"
+
+G_BEGIN_DECLS
+
+int ot_opendirat (int dfd, const char *path, gboolean follow);
+gboolean ot_gopendirat (int             dfd,
+                        const char     *path,
+                        gboolean        follow,
+                        int            *out_fd,
+                        GError        **error);
+
+G_END_DECLS
+

src/libotutil/otutil.h

@@ -40,6 +40,7 @@
 #include <ot-waitable-queue.h>
 #include <ot-keyfile-utils.h>
 #include <ot-gio-utils.h>
+#include <ot-fs-utils.h>
 #include <ot-opt-utils.h>
 #include <ot-unix-utils.h>
 #include <ot-variant-utils.h>