[Minor] Allow to convert mempool into raw pointer

src/lua/lua_mempool.c

@@ -109,6 +109,13 @@ LUA_FUNCTION_DEF (mempool, has_variable);
  * @return {boolean} `true` if variable exists and has been removed
  */
 LUA_FUNCTION_DEF (mempool, delete_variable);
+/**
+ * @method mempool:topointer()
+ *
+ * Returns raw C pointer (lightuserdata) associated with mempool. This might be
+ * broken with luajit and GC64, use with caution.
+ */
+LUA_FUNCTION_DEF (mempool, topointer);
 
 static const struct luaL_reg mempoollib_m[] = {
 	LUA_INTERFACE_DEF (mempool, add_destructor),
@@ -119,6 +126,7 @@ static const struct luaL_reg mempoollib_m[] = {
 	LUA_INTERFACE_DEF (mempool, get_variable),
 	LUA_INTERFACE_DEF (mempool, has_variable),
 	LUA_INTERFACE_DEF (mempool, delete_variable),
+	LUA_INTERFACE_DEF (mempool, topointer),
 	LUA_INTERFACE_DEF (mempool, delete),
 	{"destroy", lua_mempool_delete},
 	{"__tostring", rspamd_lua_class_tostring},
@@ -570,6 +578,23 @@ lua_mempool_delete_variable (lua_State *L)
 	return 1;
 }
 
+static gint
+lua_mempool_topointer (lua_State *L)
+{
+	LUA_TRACE_POINT;
+	rspamd_mempool_t *pool = rspamd_lua_check_mempool (L, 1);
+
+	if (pool) {
+		/* XXX: this might cause issues on arm64 and LuaJIT */
+		lua_pushlightuserdata (L, pool);
+	}
+	else {
+		return luaL_error (L, "invalid arguments");
+	}
+
+	return 1;
+}
+
 static gint
 lua_load_mempool (lua_State * L)
 {