degesch: add a stubbed Lua plugin loader

CMakeLists.txt

@@ -38,6 +38,20 @@ list (APPEND project_libraries ${libssl_LIBRARIES})
 include_directories (${libssl_INCLUDE_DIRS})
 link_directories (${libssl_LIBRARY_DIRS})
 
+# FIXME: other Lua versions may be acceptable, don't know yet
+pkg_search_module (lua lua5.3 lua-5.3 lua>=5.3)
+option (WITH_LUA "Enable experimental support for Lua plugins" ${lua_FOUND})
+
+if (WITH_LUA)
+	if (NOT lua_FOUND)
+		message (FATAL_ERROR "Lua library not found")
+	endif (NOT lua_FOUND)
+
+	list (APPEND project_libraries ${lua_LIBRARIES})
+	include_directories (${lua_INCLUDE_DIRS})
+	link_directories (${lua_LIBRARY_DIRS})
+endif (WITH_LUA)
+
 # -lpthread is only there for debugging (gdb & errno)
 # -lrt is only for glibc < 2.17
 # -liconv may or may not be a part of libc
@@ -75,13 +89,9 @@ elseif (WANT_LIBEDIT)
 endif ((WANT_READLINE AND WANT_LIBEDIT) OR (NOT WANT_READLINE AND NOT WANT_LIBEDIT))
 
 # Generate a configuration file
-if (WANT_READLINE)
-	set (HAVE_READLINE 1)
-endif (WANT_READLINE)
-
-if (WANT_LIBEDIT)
-	set (HAVE_EDITLINE 1)
-endif (WANT_LIBEDIT)
+set (HAVE_READLINE "${WANT_READLINE}")
+set (HAVE_EDITLINE "${WANT_LIBEDIT}")
+set (HAVE_LUA      "${WITH_LUA}")
 
 include (GNUInstallDirs)
 set (plugin_dir ${CMAKE_INSTALL_LIBDIR}/${PROJECT_NAME})

config.h.in

@@ -6,5 +6,6 @@
 
 #cmakedefine HAVE_READLINE
 #cmakedefine HAVE_EDITLINE
+#cmakedefine HAVE_LUA
 
 #endif  // ! CONFIG_H

degesch.c

@@ -79,6 +79,12 @@ enum
 #include <histedit.h>
 #endif // HAVE_EDITLINE
 
+#ifdef HAVE_LUA
+#include <lua.h>
+#include <lualib.h>
+#include <lauxlib.h>
+#endif // HAVE_LUA
+
 /// Some arbitrary limit for the history file
 #define HISTORY_LIMIT 10000
 
@@ -7129,6 +7135,95 @@ server_rename (struct app_context *ctx, struct server *s, const char *new_name)
 	}
 }
 
+// --- Lua ---------------------------------------------------------------------
+
+#ifdef HAVE_LUA
+
+struct lua_plugin
+{
+	struct plugin super;                ///< The structure we're deriving
+	struct app_context *ctx;            ///< Application context
+	lua_State *L;                       ///< Lua state
+};
+
+static void
+lua_plugin_free (struct plugin *self_)
+{
+	struct lua_plugin *self = (struct lua_plugin *) self_;
+	lua_close (self->L);
+}
+
+struct plugin_vtable lua_plugin_vtable =
+{
+	.free = lua_plugin_free,
+};
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+
+static void *
+lua_plugin_alloc (void *ud, void *ptr, size_t o_size, size_t n_size)
+{
+	(void) ud;
+	(void) o_size;
+
+	if (n_size)
+		return realloc (ptr, n_size);
+
+	free (ptr);
+	return NULL;
+}
+
+static int
+lua_plugin_panic (lua_State *L)
+{
+	// XXX: we might be able to do something better
+	print_fatal ("Lua panicked: %s", lua_tostring (L, -1));
+	lua_close (L);
+	exit (EXIT_FAILURE);
+	return 0;
+}
+
+static luaL_Reg lua_plugin_library[] =
+{
+	{ NULL,         NULL                  },
+};
+
+static struct plugin *
+lua_plugin_load (struct app_context *ctx, const char *filename,
+	struct error **e)
+{
+	lua_State *L = lua_newstate (lua_plugin_alloc, NULL);
+	if (!L)
+	{
+		error_set (e, "Lua initialization failed");
+		return NULL;
+	}
+
+	lua_atpanic (L, lua_plugin_panic);
+	luaL_openlibs (L);
+
+	luaL_newlib (L, lua_plugin_library);
+	lua_setglobal (L, PROGRAM_NAME);
+
+	int ret;
+	if ((ret = luaL_loadfile (L, filename))
+	 || (ret = lua_pcall (L, 0, 0, 0)))
+	{
+		error_set (e, "%s: %s", "Lua", lua_tostring (L, -1));
+		lua_close (L);
+		return NULL;
+	}
+
+	struct lua_plugin *plugin = xcalloc (1, sizeof *plugin);
+	plugin->super.name = NULL;
+	plugin->super.vtable = &lua_plugin_vtable;
+	plugin->ctx = ctx;
+	plugin->L = L;
+	return &plugin->super;
+}
+
+#endif // HAVE_LUA
+
 // --- Plugins -----------------------------------------------------------------
 
 typedef struct plugin *(*plugin_load_fn)
@@ -7138,6 +7233,9 @@ typedef struct plugin *(*plugin_load_fn)
 // however this possibility is just a byproduct of abstraction
 static plugin_load_fn g_plugin_loaders[] =
 {
+#ifdef HAVE_LUA
+	lua_plugin_load,
+#endif // HAVE_LUA
 };
 
 static struct plugin *