kbx: Add framework for the SEARCH command

* kbx/backend-kbx.c: New.
* kbx/backend-support.c: New.
* kbx/backend.h: New.
* kbx/frontend.c: New.
* kbx/frontend.h: New.
* kbx/kbxserver.c: Implement SEARCH and NEXT command.
* kbx/keybox-search-desc.h (enum pubkey_types): New.
* kbx/keybox-search.c (keybox_get_data): New.
* kbx/keyboxd.c (main): Add a standard resource.

Signed-off-by: Werner Koch <wk@gnupg.org>

kbx/frontend.h

@@ -0,0 +1,36 @@
+/* frontend.h - Definitions for the keyboxd frontend
+ * Copyright (C) 2019 g10 Code GmbH
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef KBX_FRONTEND_H
+#define KBX_FRONTEND_H
+
+#include "keybox-search-desc.h"
+
+
+gpg_error_t kbxd_add_resource  (ctrl_t ctrl,
+                                const char *filename_arg, int readonly);
+
+void kbxd_release_session_info (ctrl_t ctrl);
+
+gpg_error_t kbxd_search (ctrl_t ctrl,
+                         KEYDB_SEARCH_DESC *desc, unsigned int ndesc,
+                         int reset);
+
+
+#endif /*KBX_FRONTEND_H*/