/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//! Routines for handling measuring the memory usage of arbitrary DOM nodes.

use dom::bindings::conversions::get_dom_class;
use dom::bindings::reflector::Reflectable;
use heapsize::{HeapSizeOf, heap_size_of};
use std::os::raw::c_void;

// This is equivalent to measuring a Box<T>, except that DOM objects lose their
// associated box in order to stash their pointers in a reserved slot of their
// JS reflector.
#[allow(unsafe_code)]
pub fn heap_size_of_self_and_children<T: Reflectable + HeapSizeOf>(obj: &T) -> usize {
    unsafe {
        let class = get_dom_class(obj.reflector().get_jsobject().get()).unwrap();
        (class.heap_size_of)(obj as *const T as *const c_void)
    }
}

/// Used by codegen to include the pointer to the `HeapSizeOf` implementation of each
/// IDL interface. This way we don't have to find the most-derived interface of DOM
/// objects by hand in code.
#[allow(unsafe_code)]
pub unsafe fn heap_size_of_raw_self_and_children<T: HeapSizeOf>(obj: *const c_void) -> usize {
    heap_size_of(obj) + (*(obj as *const T)).heap_size_of_children()
}