1 files changed, 16 insertions, 0 deletions

diff --git a/src/compat.c b/src/compat.c
index 6f98854..2d2bec9 100644
--- a/src/compat.c
+++ b/src/compat.c
@@ -14,4 +14,20 @@ void luaL_setfuncs(lua_State *L, const luaL_Reg *l, int nup) {
     }
     lua_pop(L, nup);  /* remove upvalues */
 }
+
+void *luaL_testudata(lua_State *L, int ud, const char *tname) {
+    void *p = lua_touserdata(L, ud);
+    if (p != NULL) {  /* Check for userdata */
+        if (lua_getmetatable(L, ud)) {  /* Does it have a metatable? */
+            lua_getfield(L, LUA_REGISTRYINDEX, tname);  /* Get metatable we're looking for */
+            if (lua_rawequal(L, -1, -2)) {  /* Compare metatables */
+                lua_pop(L, 2);  /* Remove metatables from stack */
+                return p;
+            }
+            lua_pop(L, 2);  /* Remove metatables from stack */
+        }
+    }
+    return NULL;  /* Return NULL if check fails */
+}
+
 #endif