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: park.rs
    path of file: ./repos/may/src
    
    the code of the file until where you have to start completion: use std::fmt;
use std::io::ErrorKind;
use std::ptr;
use std::sync::atomic::{AtomicBool, AtomicPtr, Ordering};
use std::sync::Arc;
use std::time::Duration;

use crate::cancel::Cancel;
use crate::coroutine_impl::{co_cancel_data, run_coroutine, CoroutineImpl, EventSource};
use crate::scheduler::get_scheduler;
use crate::sync::atomic_dur::AtomicDuration;
use crate::sync::AtomicOption;
use crate::timeout_list::TimeoutHandle;
use crate::yield_now::{get_co_para, yield_now, yield_with};

#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub enum ParkError {
    Canceled,
    Timeout,
}

pub struct DropGuard<'a>(&'a Park);
pub struct Park {
    // the coroutine that waiting for this park instance
    wait_co: Arc<AtomicOption<CoroutineImpl>>,
    // when true means the Park no need to block
    state: AtomicBool,
    // control how to deal with the cancellation, usually init one time
    check_cancel: AtomicBool,
    // timeout settings in 
    
    fn subscribe(&mut self, co: CoroutineImpl) {
        let cancel = co_cancel_data(&co);
        // if we share the same park, the previous timer may wake up it by false
        // if we not deleted the timer in time
        let timeout_handle = self
            .timeout
            .take()
            .map(|dur| get_scheduler().add_timer(dur, self.wait_co.clone()));
        self.set_timeout_handle(timeout_handle);

        let _g = self.delay_drop();

        // register the coroutine
        unsafe { self.wait_co.unsync_store(co) };

        // re-check the state, only clear once after resume
        if self.state.load(Ordering::Acquire) {
            // here may have recursive call for subscribe
            // normally the recursion depth is not too deep
            return self.fast_wake_up();
        }

        // register the cancel data
        cancel.set_co(self.wait_co.clone());
        // re-check the cancel status
        if cancel.is_canceled() {
            unsafe { cancel.cancel() };
        }
    }