You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/gosub-engine/crates/gosub_bindings/src
    
    the code of the file until where you have to start completion: use std::ffi::c_char;
use std::ffi::CStr;
use std::ptr;

pub mod wrapper;

use gosub_html5::parser::document::{Document, DocumentBuilder};
use gosub_html5::parser::Html5Parser;
use gosub_rendering::render_tree::{Node, NodeType, RenderTree, TreeIterator};
use gosub_shared::bytes::{CharIterator, Confidence, Encoding};
use wrapper::node::CNode;

/// Initialize a render tree and return an owning pointer to it.
/// If the HTML fails to parse or the html string fails t
    
pub unsafe extern "C" fn gosub_rendertree_init(html: *const c_char) -> *mut RenderTree {
    let html_str = unsafe {
        if let Ok(html_str) = CStr::from_ptr(html).to_str() {
            html_str
        } else {
            return ptr::null_mut();
        }
    };
    let mut chars = CharIterator::new();
    chars.read_from_str(html_str, Some(Encoding::UTF8));
    chars.set_confidence(Confidence::Certain);

    let doc = DocumentBuilder::new_document(None);
    let parse_result = Html5Parser::parse_document(&mut chars, Document::clone(&doc), None);

    if parse_result.is_ok() {
        let mut rendertree = Box::new(RenderTree::new(&doc));
        rendertree.build();

        Box::into_raw(rendertree)
    } else {
        ptr::null_mut()
    }
}