wslua: register attributes along with their class

At the moment, wslua first registers a class and then adds its
attributes in a second step. This registration creates empty __getters
and __setters tables which are later populated with the getter and
setter methods of the attributes.

Looking at the code and the comments, it seems that this was meant to be
a temporary solution. Eventually, attributes should be stored in
wslua_class' attrs field. The code to read and write attributes was
already updated to handle this.

Add new macros WSLUA_REGISTER_CLASS/_META_WITH_ATTRS that store the
attributes in wslua_class. Defining new macros is simpler than modifying
WSLUA_REGISTER_CLASS/_META to register attributes. If we did the latter,
we'd have to add an empty attribute list for all classes without
attributes.

We can now drop the WSLUA_REGISTER_ATTRIBUTES macro and the
wslua_reg_attributes function.

Using this new way of registering attributes, the __getters and
__setters tables are still available. The tests is the test suite that
rely on those tables still pass.

Change-Id: I526b9116435645c9c54ab69a05c3c7f3d459ec33
Reviewed-on: https://code.wireshark.org/review/31417
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Petri-Dish: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Petri Dish Buildbot
Reviewed-by: Peter Wu <peter@lekensteyn.nl>

epan/wslua/wslua.h

@@ -416,39 +416,36 @@ extern int wslua_reg_attributes(lua_State *L, const wslua_attribute_table *t, gb
     /* pop the metatable */ \
     lua_pop(L, 1)
 
-#define WSLUA_REGISTER_META(C) { \
+#define __WSLUA_REGISTER_META(C, ATTRS_BLOCK) { \
     const wslua_class C ## _class = { \
         .name               = #C, \
         .instance_meta      = C ## _meta, \
+        ATTRS_BLOCK \
     }; \
     wslua_register_classinstance_meta(L, &C ## _class); \
     WSLUA_REGISTER_GC(C); \
 }
 
-#define WSLUA_REGISTER_CLASS(C) { \
+#define WSLUA_REGISTER_META(C)  __WSLUA_REGISTER_META(C,)
+#define WSLUA_REGISTER_META_WITH_ATTRS(C) \
+    __WSLUA_REGISTER_META(C, .attrs = C ## _attributes)
+
+#define __WSLUA_REGISTER_CLASS(C, ATTRS_BLOCK) { \
     const wslua_class C ## _class = { \
         .name               = #C, \
         .class_methods      = C ## _methods, \
         .class_meta         = C ## _meta, \
         .instance_methods   = C ## _methods, \
         .instance_meta      = C ## _meta, \
+        ATTRS_BLOCK \
     }; \
     wslua_register_class(L, &C ## _class); \
     WSLUA_REGISTER_GC(C); \
 }
 
-/* see comments for wslua_reg_attributes and wslua_attribute_dispatcher to see how this attribute stuff works */
-#define WSLUA_REGISTER_ATTRIBUTES(C) { \
-    /* get metatable from Lua registry */ \
-    luaL_getmetatable(L, #C); \
-    if (lua_isnil(L, -1)) { \
-        g_error("Attempt to register attributes without a pre-existing metatable for '%s' in Lua registry\n", #C); \
-    } \
-    /* register the getters/setters in their tables */ \
-    wslua_reg_attributes(L, C##_attributes, TRUE); \
-    wslua_reg_attributes(L, C##_attributes, FALSE); \
-    lua_pop(L, 1); /* pop the metatable */ \
-}
+#define WSLUA_REGISTER_CLASS(C)  __WSLUA_REGISTER_CLASS(C,)
+#define WSLUA_REGISTER_CLASS_WITH_ATTRS(C) \
+    __WSLUA_REGISTER_CLASS(C, .attrs = C ## _attributes)
 
 #define WSLUA_INIT(L) \
     luaL_openlibs(L); \

epan/wslua/wslua_capture_info.c

@@ -292,8 +292,7 @@ WSLUA_META CaptureInfo_meta[] = {
 };
 
 int CaptureInfo_register(lua_State* L) {
-    WSLUA_REGISTER_META(CaptureInfo);
-    WSLUA_REGISTER_ATTRIBUTES(CaptureInfo);
+    WSLUA_REGISTER_META_WITH_ATTRS(CaptureInfo);
     return 0;
 }
 
@@ -502,8 +501,7 @@ WSLUA_META CaptureInfoConst_meta[] = {
 };
 
 int CaptureInfoConst_register(lua_State* L) {
-    WSLUA_REGISTER_META(CaptureInfoConst);
-    WSLUA_REGISTER_ATTRIBUTES(CaptureInfoConst);
+    WSLUA_REGISTER_META_WITH_ATTRS(CaptureInfoConst);
     return 0;
 }
 

epan/wslua/wslua_field.c

@@ -472,8 +472,7 @@ WSLUA_META FieldInfo_meta[] = {
 };
 
 int FieldInfo_register(lua_State* L) {
-    WSLUA_REGISTER_META(FieldInfo);
-    WSLUA_REGISTER_ATTRIBUTES(FieldInfo);
+    WSLUA_REGISTER_META_WITH_ATTRS(FieldInfo);
     return 0;
 }
 
@@ -794,8 +793,7 @@ int Field_register(lua_State* L) {
 
     wanted_fields = g_ptr_array_new();
 
-    WSLUA_REGISTER_CLASS(Field);
-    WSLUA_REGISTER_ATTRIBUTES(Field);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(Field);
     outstanding_FieldInfo = g_ptr_array_new();
 
     return 0;

epan/wslua/wslua_file.c

@@ -501,8 +501,7 @@ WSLUA_META File_meta[] = {
 };
 
 int File_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(File);
-    WSLUA_REGISTER_ATTRIBUTES(File);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(File);
     return 0;
 }
 

epan/wslua/wslua_file_handler.c

@@ -1027,8 +1027,7 @@ WSLUA_META FileHandler_meta[] = {
 };
 
 int FileHandler_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(FileHandler);
-    WSLUA_REGISTER_ATTRIBUTES(FileHandler);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(FileHandler);
     return 0;
 }
 

epan/wslua/wslua_frame_info.c

@@ -239,8 +239,7 @@ WSLUA_META FrameInfo_meta[] = {
 };
 
 int FrameInfo_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(FrameInfo);
-    WSLUA_REGISTER_ATTRIBUTES(FrameInfo);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(FrameInfo);
     return 0;
 }
 
@@ -384,8 +383,7 @@ WSLUA_META FrameInfoConst_meta[] = {
 };
 
 int FrameInfoConst_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(FrameInfoConst);
-    WSLUA_REGISTER_ATTRIBUTES(FrameInfoConst);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(FrameInfoConst);
     return 0;
 }
 

epan/wslua/wslua_internals.c

@@ -229,45 +229,6 @@ gboolean wslua_get_field(lua_State *L, int idx, const gchar *name) {
     return result;
 }
 
-
-/**
- * This is a transition function that sets attributes on classes. It must be
- * replaced by setting the attributes in the wslua_class structure such that
- * WSLUA_REGISTER_ATTRIBUTES can be nuked.
- */
-int wslua_reg_attributes(lua_State *L, const wslua_attribute_table *t, gboolean is_getter) {
-    const gchar *metafield = is_getter ? "__index" : "__newindex";
-
-    /* assume __index/__newindex exists and index 1 is a metatable */
-    lua_rawgetfield(L, -1, metafield);
-    if (lua_isnil(L, -1)) {
-        g_error("%s expected in metatable, found none!\n", metafield);
-    }
-    lua_pop(L, 1);
-
-    /* Find table to add properties. */
-    metafield = is_getter ? "__getters" : "__setters";
-    lua_rawgetfield(L, -1, metafield);
-    if (!lua_istable(L, -1)) {
-        g_error("Property %s is not found in metatable!\n", metafield);
-    }
-
-    /* Fill the getter/setter table with given functions. Being a transition
-     * function that will be removed later, this does not perform duplicate
-     * keys detection. */
-    for (; t->fieldname != NULL; t++) {
-        lua_CFunction cfunc = is_getter ? t->getfunc : t->setfunc;
-        if (cfunc) {
-            lua_pushcfunction(L, cfunc);
-            lua_rawsetfield(L, -2, t->fieldname);
-        }
-    }
-
-    /* Drop __getters/__setters table */
-    lua_pop(L, 1);
-    return 0;
-}
-
 /**
  * The __index metamethod for classes. Expected upvalues: class name.
  */

epan/wslua/wslua_listener.c

@@ -375,8 +375,7 @@ int Listener_register(lua_State* L) {
 
     listeners = g_ptr_array_new();
 
-    WSLUA_REGISTER_CLASS(Listener);
-    WSLUA_REGISTER_ATTRIBUTES(Listener);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(Listener);
     return 0;
 }
 

epan/wslua/wslua_nstime.c

@@ -216,8 +216,7 @@ WSLUA_META NSTime_meta[] = {
 };
 
 int NSTime_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(NSTime);
-    WSLUA_REGISTER_ATTRIBUTES(NSTime);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(NSTime);
     return 0;
 }
 

epan/wslua/wslua_pinfo.c

@@ -462,8 +462,7 @@ WSLUA_META Pinfo_meta[] = {
 };
 
 int Pinfo_register(lua_State* L) {
-    WSLUA_REGISTER_META(Pinfo);
-    WSLUA_REGISTER_ATTRIBUTES(Pinfo);
+    WSLUA_REGISTER_META_WITH_ATTRS(Pinfo);
     outstanding_Pinfo = g_ptr_array_new();
     outstanding_PrivateTable = g_ptr_array_new();
     return 0;

epan/wslua/wslua_proto.c

@@ -549,8 +549,7 @@ WSLUA_META Proto_meta[] = {
 };
 
 int Proto_register(lua_State* L) {
-    WSLUA_REGISTER_CLASS(Proto);
-    WSLUA_REGISTER_ATTRIBUTES(Proto);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(Proto);
 
     outstanding_FuncSavers = g_ptr_array_new();
 

epan/wslua/wslua_tree.c

@@ -964,8 +964,7 @@ WSLUA_META TreeItem_meta[] = {
 int TreeItem_register(lua_State *L) {
     gint* etts[] = { &wslua_ett };
     wslua_ett = -1; /* Reset to support reload Lua plugins */
-    WSLUA_REGISTER_CLASS(TreeItem);
-    WSLUA_REGISTER_ATTRIBUTES(TreeItem);
+    WSLUA_REGISTER_CLASS_WITH_ATTRS(TreeItem);
     outstanding_TreeItem = g_ptr_array_new();
     proto_register_subtree_array(etts,1);
     return 0;