ffi.getmetatable
- From: Ronan Collobert <ronan@xxxxxxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Fri, 21 Nov 2014 15:23:45 -0800
Hi,
At this time there is no (easy) way with luajit+ffi to get the metatable of a
cdata/ctype. I understand the notion of metatable is ambiguous here, as the
metatable given by the user through ffi.metatype() is not the actual one on the
cdata (a global ffi-specific metatable that can be obtained by
debug.getmetatable).
Reading the mailing list, I saw several people encountered the same issue (see
for e.g. https://github.com/corsix/ffi-reflect and reflect.getmetatable).
Do you think it would be reasonable to have a ffi.getmetatable(ctype) function,
which returns the original “metatable” given by user through ffi.metatype?
(code in attachment) — If yes, I can work on the compiled version. I sincerely
feel this is missing in the current ffi lib.
Thanks.
Ronan.
--- a/src/lib_ffi.c
+++ b/src/lib_ffi.c
@@ -558,6 +558,18 @@ LJLIB_CF(ffi_typeof) LJLIB_REC(.)
return 1;
}
+LJLIB_CF(ffi_getmetatable)
+{
+ CTState *cts = ctype_cts(L);
+ CTypeID id = ffi_checkctype(L, cts, NULL);
+ cTValue *tv = lj_tab_getinth(cts->miscmap, -(int32_t)id);
+ if (tv && !tvisnil(tv)) {
+ copyTV(L, L->top-1, tv);
+ return 1;
+ }
+ return 0;
+}
+
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