use std::io;
use std::mem::{self, ManuallyDrop};
use std::ptr;
use std::task::Waker;
use parking_lot::Mutex;
use crate::Cancellation;
use State::*;
pub struct Completion {
state: ManuallyDrop<Box<Mutex<State>>>,
}
enum State {
Submitted(Waker),
Completed(io::Result<usize>),
Cancelled(Cancellation),
Empty,
}
impl Completion {
pub fn new(waker: Waker) -> Completion {
Completion {
state: ManuallyDrop::new(Box::new(Mutex::new(Submitted(waker)))),
}
}
pub fn addr(&self) -> u64 {
&**self.state as *const Mutex<State> as usize as u64
}
pub fn check(self, waker: &Waker) -> Result<io::Result<usize>, Completion> {
let mut state = self.state.lock();
match mem::replace(&mut *state, State::Empty) {
Submitted(old_waker) => {
let waker = if old_waker.will_wake(waker) { old_waker } else { waker.clone() };
*state = Submitted(waker);
drop(state);
Err(self)
}
Completed(result) => {
drop(state);
drop(ManuallyDrop::into_inner(self.state));
Ok(result)
}
_ => unreachable!()
}
}
pub fn cancel(self, callback: Cancellation) {
let mut state = self.state.lock();
match &*state {
Submitted(_) => {
*state = Cancelled(callback);
}
Completed(_) => {
drop(callback);
drop(state);
drop(ManuallyDrop::into_inner(self.state));
}
_ => unreachable!()
}
}
}
pub unsafe fn complete(cqe: iou::CompletionQueueEvent) {
if cqe.is_timeout() { return; }
let result = cqe.result();
let completion = cqe.user_data() as *mut Mutex<State>;
if completion != ptr::null_mut() {
let state: &Mutex<State> = &*completion;
let mut state = state.lock();
match mem::replace(&mut *state, State::Empty) {
Submitted(waker) => {
*state = Completed(result);
waker.wake();
}
Cancelled(callback) => {
drop(callback);
drop(state);
drop(Box::from_raw(completion));
}
_ => unreachable!()
}
}
}