Function detect_circular_reference

libs/llrt_json/src/stringify.rs:316–372

(
    ctx: &Ctx<'_>,
    value: &Object<'_>,
    key: Option<&str>,
    index: Option<usize>,
    parent: Option<&Object<'_>>,
    ancestors: &mut Vec<(usize, Rc<str>)>,
    itoa_buffer: &mut itoa::Bu

#[cold]
fn detect_circular_reference(
    ctx: &Ctx<'_>,
    value: &Object<'_>,
    key: Option<&str>,
    index: Option<usize>,
    parent: Option<&Object<'_>>,
    ancestors: &mut Vec<(usize, Rc<str>)>,
    itoa_buffer: &mut itoa::Buffer,
) -> Result<()> {
    let parent_ptr = unsafe { qjs::JS_VALUE_GET_PTR(parent.unwrap_unchecked().as_raw()) as usize };
    let current_ptr = unsafe { qjs::JS_VALUE_GET_PTR(value.as_raw()) as usize };

    while !ancestors.is_empty()
        && match ancestors.last() {
            Some((ptr, _)) => ptr != &parent_ptr,
            _ => false,
        }
    {
        ancestors.pop();
    }

    if ancestors.iter().any(|(ptr, _)| ptr == &current_ptr) {
        let mut iter = ancestors.iter_mut();

        let first = &unsafe { iter.next().unwrap_unchecked() }.1;

        let mut message = iter.rev().take(4).rev().fold(
            String::from("Circular reference detected at: \".."),
            |mut acc, (_, key)| {
                if !key.starts_with('[') {
                    acc.push('.');
                }
                acc.push_str(key);
                acc
            },
        );

        if !first.starts_with('[') {
            message.push('.');
        }

        message.push_str(first);
        message.push('"');

        return Err(Exception::throw_type(ctx, &message));
    }
    ancestors.push((
        current_ptr,
        key.map(|k| k.into()).unwrap_or_else(|| {
            ["[", itoa_buffer.format(index.unwrap_or_default()), "]"]
                .concat()
                .into()
        }),
    ));

    Ok(())
}